Showing papers in "Applied Catalysis B-environmental in 2022"

In situ construction of S-scheme AgBr/BiOBr heterojunction with surface oxygen vacancy for boosting photocatalytic CO2 reduction with H2O

Abstract: S-scheme heterojunction has attracted much attention due to its unique structure and interface interaction. Herein, AgBr/BiOBr heterojunction with surface oxygen vacancies (OVs) was in situ synthesized by a facile chemical method. It was found that the evolution rates of photoreduction of CO2 to CO and CH4 with 0.33AB are 212.6 and 5.7 μmol g−1 h−1 respectively, which are 9.2 and 5.2 times higher than those of pure BiOBr. It was demonstrated that the S-scheme band structure could improve the utilization of sunlight, increase the reduction power of photogenerated electrons, and enhance the separation and transfer of photogenerated charge carriers. Furthermore, the OVs on the surface of BiOBr for AgBr/BiOBr heterojunction are conductive to the adsorption and activation of CO2 molecules. The synergetic effect of S-scheme band structure and OVs on photocatalytic reduction of CO2 was discussed. The work provides a facile method for in situ construction of S-scheme heterojunction with defect for CO2 photoreduction.

In situ construction of S-scheme AgBr/BiOBr heterojunction with surface oxygen vacancy for boosting photocatalytic CO2 reduction with H2O

Abstract: S-scheme heterojunction has attracted much attention due to its unique structure and interface interaction. Herein, AgBr/BiOBr heterojunction with surface oxygen vacancies (OVs) was in situ synthesized by a facile chemical method. It was found that the evolution rates of photoreduction of CO2 to CO and CH4 with 0.33AB are 212.6 and 5.7 μmol g−1 h−1 respectively, which are 9.2 and 5.2 times higher than those of pure BiOBr. It was demonstrated that the S-scheme band structure could improve the utilization of sunlight, increase the reduction power of photogenerated electrons, and enhance the separation and transfer of photogenerated charge carriers. Furthermore, the OVs on the surface of BiOBr for AgBr/BiOBr heterojunction are conductive to the adsorption and activation of CO2 molecules. The synergetic effect of S-scheme band structure and OVs on photocatalytic reduction of CO2 was discussed. The work provides a facile method for in situ construction of S-scheme heterojunction with defect for CO2 photoreduction.

Photo-Fenton degradation of tetracycline over Z-scheme Fe-g-C3N4/Bi2WO6 heterojunctions: Mechanism insight, degradation pathways and DFT calculation

Abstract: Herein, Fe-g-C3N4/Bi2WO6 Z-scheme heterojunction is elaborately designed to build a photo-Fenton system for the degradation of tetracycline (TC). In this study, the H2O2 decomposition performance of the Z-scheme heterojunction has been improved due to the doping of iron, improve photogenerated electrons transportability and facilitate spread of radicals, according to the efficacy analyses, and trapping experiment, ESR analysis as well as degradation pathways of TC. Moreover, DFT theoretical results suggest that the Z-scheme transfer route coupled with the generated photo–Fenton process builds a Z-scheme-charge-transfer platform for remarkable degradation of emerging pollutants, and the formation of Fe-N4 sites induces a spin polarization of the material and also introduces a defect state in the original forbidden band, which leads to extremely activity for the removal of TC in the photo-Fenton system. The study shows that 1O2 and •O2− are the main active species participating in the degradation process.

Dual optimization approach to Mo single atom dispersed g-C3N4 photocatalyst: Morphology and defect evolution

Abstract: Reasonable regulation of the interaction between metal center and the ligand to achieve a high-density atomic loading without agglomeration has been the formidable challenge to the development of single-atom catalysts (SACs). Herein, an advanced photocatalyst based on N-vacancy (Nv) tubular porous g-C3N4 (TCN) decorated with atomically dispersed Mo (Mo/Nv-TCN) is synthesized. The large specific surface area of the tubular morphology contributes to suppress the agglomeration of Mo atoms, while the N defect induces the formation of specific stable Mo-2 C/2 N configuration between the light absorbers and the Mo sites. As the active center of the photocatalytic reaction, single Mo atom causes the directional transfer of local charges on the surface of the support, while the Mo-2 C/2 N bond acts as a bridge for photoexcited charge transfer. As a result, the precisely designed Mo SACs system shows remarkable photoelectric properties and renders excellent photocatalytic performance for tetracycline (TC) degradation under visible light irradiation.

Defective g-C3N4/covalent organic framework van der Waals heterojunction toward highly efficient S-scheme CO2 photoreduction

Abstract: In this work, a novel van der Waals (vdW) heterojunction composite combining g-C3N4 with nitrogen vacancies and Tp-Tta COF manifests effective interface contact area and excellent photocatalytic CO2 reduction performance. First-principles density functional theory calculation and experimental results suggest that the presence of nitrogen vacancies in g-C3N4 can widen the Fermi level gap between C3N4 (NH) and Tp-Tta COF, promoting the recombination of invalid photogenerated carriers through S-scheme pathway. Benefitted from the accelerated transfer of photogenerated charges at the vdW heterostructure interface, the deactivation of oxygen vacancies in C3N4 (NH)/COF is prevented and much higher photocatalytic activity and stability are obtained. The efficient electron transfer and the affinity of Tp-Tta for CO2 are beneficial to the enhanced CO selectivity. This work provides insights for the design of S-scheme heterojunction photocatalyst for CO2 reduction.

Rational design of multifunctional electrocatalyst: An approach towards efficient overall water splitting and rechargeable flexible solid-state zinc–air battery

Abstract: Constructing an electrocatalyst with highly durable active and cost-effective core-shell with a porous carbon nanosheet for the development of high efficiency energy conversion and storage devices. Herein, we developed core-shell nickel-iron oxide on a highly porous N-doped carbon nanosheet (CS-NFO@PNC) via a facile solvothermal calcination route. The optimized CS-NFO@PNC-700 showed remarkable electrocatalytic activity towards ORR (0.85 V vs RHE), OER ƞ10 = 217 mV, and HER ƞ10 = 200 mV with excellent durability towards the corresponding half-cell reactions. Further, we investigated the ORR, OER, and HER mechanistic pathways of the electrocatalyst using the density functional theory. Finally, we fabricated a rechargeable liquid electrolyte-based zinc–air battery with CS-NFO@PNC-700 as the cathode which displayed an improved power density of 130 mW cm−2 at 217 mA cm−2 with excellent durability of 180 h. The rechargeable flexible quasi-solid-state zinc–air battery with CS-NFO@PNC-700 air cathode, which exhibited excellent long term durability over 40 h at 5 mA cm−2.

Graphene Aerogel-Based NiAl-LDH/g-C3N4 With Ultratight Sheet-Sheet Heterojunction for Excellent Visible-Light Photocatalytic Activity of CO2 Reduction

Abstract: NiAl-LDH (NALDH) nanosheets were in intimate contact with g-C3N4 (CN) nanosheets to form ultratight sheet-sheet heterojunctions, which interweaved into network framework with introduction of the graphene aerogel (GA). Notably, the NALDH/CN/GA-20 showed a remarkable CO production rate of 28.83 μmol·g−1·h−1 under visible light irradiation, which was 24 and 16 times those of pure NALDH and bare CN, respectively. Furthermore, it was far exceeding the reported conventional CO2 photocatalytic reduction efficiency. The ultratight sheet-sheet heterojunctions not only shorten the charge transmission distance, but result abundant active sites and coupling large interfaces. The unique structure promoted the transport and separation of photogenerated carriers, and facilitated effective mass transport and light absorption. Multi electron series reduction mechanism based on type-II photocatalytic system was proposed to explain the CO2 reduction pathway. This work provides insight for designing photocatalysts with ideal performance for CO2 reduction.

Synthesis of acidic MIL-125 from plastic waste: Significant contribution of N orbital for efficient photocatalytic degradation of chlorobenzene and toluene

Abstract: Development of efficient and stable catalyst for the degradation of chlorinated volatile organic compounds (VOCs) is a hot research topic. In this study, we used plastic-based terephthalic acid for the synthesis of MIL-125, which further modified by the -NH2 and -NO2 groups. DFT calculations revealed that the N orbitals had an important contribution in reducing the band gap, leading to easier hydrogen absorption and high electron transfer efficiency. Optical studies, XPS, TRES, NH3-TPD and pyridine IR further demonstrated that the amino modification promoted the visible absorption range and acidity of MIL-125 in comparison to the nitro modification, resulting in efficient catalytic degradation of chlorobenzene and toluene, even in the presence of water. This work provides an economically feasible strategy for modifying metal organic frameworks (MOFs) and suggests the possible VOCs degradation pathways with EPR, in situ FTIR, GC-MS and TG-MS analysis.

Synergy Between Cobalt and Nickel on NiCo2O4 Nanosheets Promotes Peroxymonosulfate Activation for Efficient Norfloxacin Degradation

Abstract: Developing an ultraefficient heterogeneous catalyst for peroxymonosulfate (PMS) activation at a wide pH range is a challenge. Herein, ultrathin NiCo 2 O 4 nanosheets (NiCo 2 O 4 NS, ~1 nm), with the dominant exposure of (311) facet, was designed for PMS activation. The NiCo 2 O 4 NS/PMS system exhibited superior degradation of norfloxacin (NOR) over a wide pH range. The synergistic effects between Ni and Co were the dominant activation mechanism. Compared with Co 3 O 4 , NiCo 2 O 4 NS adsorb PMS through a unique “bridge” mode, where both Co and adjacent Ni interact with the same O atom in PMS, increasing the number of electron transfer for enhanced breakage of O O bond. NiCo 2 O 4 NS with high cycling stability, could reach 100% degradation of other typical pollutants, and showed higher degradation performance in actual wastewater. This work unveils the intrinsic origin of the superior activity of Co-Ni spinel oxides for PMS activation for the first time, and demonstrates its application potential for organic contaminants degradation. • Ultrathin magnetic NiCo 2 O 4 nanosheet was synthesized by simple annealing hydroxides. • High PMS catalytic activity with 100% pollutant removal could be achieved. • The synergy between Co and Ni on highly active crystal (311) were realized. • Ni increases the Co-O covalency to favor Co-PMS adsorption and charge transfer. • Degradation pathway and intermediates’ ecotoxicity prediction were presented.

Highly efficient adsorption and catalytic degradation of ciprofloxacin by a novel heterogeneous Fenton catalyst of hexapod-like pyrite nanosheets mineral clusters

Abstract: Herein, a novel hexapod-like pyrite nanosheets mineral cluster was prepared via a facile hydrothermal method. Compared with classical homogeneous Fenton processes, this catalyst possessed a higher adsorption capacity and catalytic activity to ciprofloxacin (20 mg/L), which could be completely degraded within 10 min at pH 4.0. •OH was the main reactive oxygen species responsible for ciprofloxacin degradation. Br− (≥ 1 mM), I− (≥ 1 mM), and high concentration of F− ions (≥ 10 mM) exhibited an inhibition effect on ciprofloxacin degradation, but the Cl− ions (0–100 mM) did not show obvious effects on ciprofloxacin removal. Thirteen intermediates were qualitatively identified, and degradation mechanism was tentatively proposed for ciprofloxacin. Several toxic intermediates were produced, but they could be fully mineralized and detoxified by this heterogeneous Fenton catalyst after 30 min reaction. The work provides a novel heterogeneous Fenton catalyst to purify and detoxify antibiotics as well as other refractory organic pollutants contaminated wastewater.

Highly efficient adsorption and catalytic degradation of ciprofloxacin by a novel heterogeneous Fenton catalyst of hexapod-like pyrite nanosheets mineral clusters

Abstract: Herein, a novel hexapod-like pyrite nanosheets mineral cluster was prepared via a facile hydrothermal method. Compared with classical homogeneous Fenton processes, this catalyst possessed a higher adsorption capacity and catalytic activity to ciprofloxacin (20 mg/L), which could be completely degraded within 10 min at pH 4.0. • OH was the main reactive oxygen species responsible for ciprofloxacin degradation. Br − (≥ 1 mM), I − (≥ 1 mM), and high concentration of F − ions (≥ 10 mM) exhibited an inhibition effect on ciprofloxacin degradation, but the Cl − ions (0–100 mM) did not show obvious effects on ciprofloxacin removal. Thirteen intermediates were qualitatively identified, and degradation mechanism was tentatively proposed for ciprofloxacin. Several toxic intermediates were produced, but they could be fully mineralized and detoxified by this heterogeneous Fenton catalyst after 30 min reaction. The work provides a novel heterogeneous Fenton catalyst to purify and detoxify antibiotics as well as other refractory organic pollutants contaminated wastewater. • A novel catalyst hexapod-like pyrite nanosheets mineral cluster was synthesized. • Ciprofloxacin was removed through adsorption and Fenton catalytic degradation. • • OH was the dominant reactive oxygen species for ciprofloxacin degradation. • Thirteen intermediates were qualitatively determined and identified. • This heterogeneous Fenton catalyst is feasible in degrading antibiotics pollution.

Biochar co-doped with nitrogen and boron switching the free radical based peroxydisulfate activation into the electron-transfer dominated nonradical process

Abstract: In this study, N/B co-doped biochars were employed as metal-free activators of peroxydisulfate (PDS) for tetracycline degradation, more importantly, the roles of dopants and the relative contribution of radical vs nonradical oxidations were comprehensively investigated. Integrating with electron paramagnetic resonance and kinetics calculations, we showed that co-doping N and B into biochars not only boosted the catalytic activity but also switched the radical PDS-activated process into the electron transfer-dominated nonradical process. Compared with pristine biochar/PDS systems (22%), the nonradical contribution of N/B co-doped biochar/PDS systems increased to 59%, exhibiting outstanding stability and selectivity. Galvanic oxidation tests and theoretical simulations unveiled that doped biochars as conductive tunnels accelerate the potential difference-driven electron transfer from the highest occupied molecular orbital of pollutants to the lowest unoccupied molecular orbital of PDS due to the lower energy gap. This study provided new insights into the critical role of heteroatom-doped carbocatalysts in PDS nonradical activation.

Metal–organic framework supported Au nanoparticles with organosilicone coating for high-efficiency electrocatalytic N2 reduction to NH3

Abstract: The development of electrocatalysts for nitrogen reduction reaction (NRR) at ambient conditions, with both high NH3 yield and Faradaic efficiency, is currently a great challenge. To this aim, a unique metal–organic framework (MOF) crystalline matrix with disulfide trimeric unit as the building block was in situ synthesized by integration of dynamic covalent chemistry and coordination chemistry. This MOF with high porosity and excellent stability could be used as a host material to encapsulate well-dispersed Au nanoparticles (NPs) with ultrafine size of 1.9 ± 0.4 nm. After surface modification of [email protected] by using organosilicone, the hydrophobic-treated [email protected] (HT [email protected]) composite shows remarkable electrocatalytic performances for NRR, with the highest NH3 yield of 49.5 μg h–1 mgcat.–1 and the state-of-the-art Faradaic efficiency of 60.9% in water medium at ambient conditions. The favorable role of MOFs with functional sulfur groups on modulating the active Au sites and the great effect of hydrophobic coatings on suppressing the competitive hydrogen evolution reaction (HER) have been further demonstrated. This work provides a universal strategy to design composite electrocatalysts for high-efficient and long-term NH3 production.

Metal–organic framework supported Au nanoparticles with organosilicone coating for high-efficiency electrocatalytic N2 reduction to NH3

Abstract: The development of electrocatalysts for nitrogen reduction reaction (NRR) at ambient conditions, with both high NH3 yield and Faradaic efficiency, is currently a great challenge. To this aim, a unique metal–organic framework (MOF) crystalline matrix with disulfide trimeric unit as the building block was in situ synthesized by integration of dynamic covalent chemistry and coordination chemistry. This MOF with high porosity and excellent stability could be used as a host material to encapsulate well-dispersed Au nanoparticles (NPs) with ultrafine size of 1.9 ± 0.4 nm. After surface modification of Au@MOF by using organosilicone, the hydrophobic-treated Au@MOF (HT Au@MOF) composite shows remarkable electrocatalytic performances for NRR, with the highest NH3 yield of 49.5 μg h–1 mgcat.–1 and the state-of-the-art Faradaic efficiency of 60.9% in water medium at ambient conditions. The favorable role of MOFs with functional sulfur groups on modulating the active Au sites and the great effect of hydrophobic coatings on suppressing the competitive hydrogen evolution reaction (HER) have been further demonstrated. This work provides a universal strategy to design composite electrocatalysts for high-efficient and long-term NH3 production.

Interfacial electronic modulation by Fe2O3/NiFe-LDHs heterostructures for efficient oxygen evolution at high current density

Abstract: Designing and fabricating well-defined heterointerface catalysts with high electrocatalytic performance for oxygen evolution reaction (OER) at the industrial grade current density still remains a huge challenge. Here the flower-like nanosheets with rich Fe2O3/NiFe-layered double hydroxides (LDHs) heterointerfaces were fabricated, and they exhibit superior catalytic activity with a very low overpotential of 220 mV for OER at the industrial grade current density of 500 mA cm− 2 and fast reaction kinetics with a small Tafel slope of 32 mV dec−1. Based on the analyses of operando Raman spectra, DFT theoretical calculations and electrochemical characterizations, the superior electrocatalytic performance of catalysts for OER at the industrial grade current density can be attributed to Fe2O3/NiFe-LDHs heterointerfaces that can obviously promote interfacial electron transfer from Ni2+ to Fe3+ and optimize d-orbit electronic configuration with eg occupancy of Ni close to the unity, resulting in moderate adsorption/desorption energies of oxygenated intermediates, and thus facilitating remarkably electrocatalytic performance and superior intrinsic kinetics for OER in alkaline media.

Fe, N-doped carbonaceous catalyst activating periodate for micropollutant removal: Significant role of electron transfer

Abstract: In this study, the performance of periodate (PI) on sulfadiazine (SDZ) degradation was evaluated using coagulation solid waste fabricated catalyst (CWBC), obtained by simple pyrolysis. SDZ effectively underwent 98.94% remove within 90 min in the CWBC/PI system. Electron transfer was the predominant mechanism due to the development of an electronic cycle among SDZ, CWBC and PI, where the O 2 •− , PFRs, and the reactive iodine species had minor roles. Density functional theory calculations identified that Fe and N could change the electron configuration and break the chemical inertness of carbonaceous material. As a result, electrons on the carbon matrix of CWBC are inclined to travel through the formed Fe–O covalent bond to PI. Further analysis demonstrated that SO 4 2− , humic acid (HA), as well as anoxic conditions greatly facilitated SDZ degradation. This study provides a facile protocol for converting coagulation waste to an efficient catalyst and provides fundamental insights into the degradation mechanisms of micropollutants by activating PI. • A carbonaceous catalyst was prepared from coagulation waste to activate periodate. • Electron transfer has a dominant effect on sulfadiazine degradation. • Fe and N could change the electron configuration of carbonaceous catalyst. • Chemisorption between Fe and PI was the key step for the catalytic process. • Sulfadiazine removal can be significantly enhanced under anoxic conditions.

Highly efficient photothermal catalysis of toluene over Co3O4/TiO2 p-n heterojunction: The crucial roles of interface defects and band structure

Abstract: The unique physicochemical properties presented in the interface of composite oxides would result in some new features. Herein, MO x /TiO 2 (M = Co, Mn, Ce, Cu, Fe) composites were constructed and successfully applied in the full spectrum light-assisted photothermal catalytic degradation of toluene. A unique p-n heterojunction with interface defects caused by lattice mismatch was constructed between TiO 2 and Co 3 O 4 . The relationship between interface properties, band structure and photothermal catalytic performance based on experimental results and theoretical calculations had been studied comprehensively. The interfacial oxygen vacancy could improve oxygen mobility and provide more surface reactive oxygen species. The built-in electric field generated by electron transfer at the interface effectively promoted electron-hole pairs migration in the opposite direction. More active radicals and holes were provided to enhance the photothermal performance of CoTi catalyst. Furthermore, the possible reaction pathway of toluene and the photothermal synergy mechanism was proposed. • Co 3 O 4 /TiO 2 p-n heterojunction was constructed for toluene photothermal catalysis. • Lattice mismatch resulted in the generation of oxygen vacancies at the interface. • The matched band structure promoted the electron migration. • Possible degradation pathway and photothermal synergistic mechanism was proposed.

Fe, N-doped carbonaceous catalyst activating periodate for micropollutant removal: Significant role of electron transfer

Abstract: In this study, the performance of periodate (PI) on sulfadiazine (SDZ) degradation was evaluated using coagulation solid waste fabricated catalyst (CWBC), obtained by simple pyrolysis. SDZ effectively underwent 98.94% remove within 90 min in the CWBC/PI system. Electron transfer was the predominant mechanism due to the development of an electronic cycle among SDZ, CWBC and PI, where the O2•−, PFRs, and the reactive iodine species had minor roles. Density functional theory calculations identified that Fe and N could change the electron configuration and break the chemical inertness of carbonaceous material. As a result, electrons on the carbon matrix of CWBC are inclined to travel through the formed Fe–O covalent bond to PI. Further analysis demonstrated that SO42−, humic acid (HA), as well as anoxic conditions greatly facilitated SDZ degradation. This study provides a facile protocol for converting coagulation waste to an efficient catalyst and provides fundamental insights into the degradation mechanisms of micropollutants by activating PI.

Graphene composites with Ru-RuO2 heterostructures: Highly efficient Mott–Schottky-type electrocatalysts for pH-universal water splitting and flexible zinc–air batteries

Abstract: Development of high-efficiency electrocatalysts for pH-universal overall water splitting is a critical step towards a sustainable hydrogen economy. Herein, graphene nanocomposites with Ru-RuO2 Mott-Schottky heterojunctions (Ru-RuO2@NPC) are prepared pyrolytically and exhibit a remarkable electrocatalytic activity at pH = 0–14 towards both oxygen/hydrogen evolution reactions and overall water splitting, as compared to commercial RuO2 and Pt/C. Ru-RuO2@NPC can also be used as an effective air cathode catalyst for flexible, rechargeable zinc-air batteries. Density functional theory calculations show that the formation of Ru-RuO2 heterojunctions moderately enhances the surface charge density of metallic Ru and brings the d states closer to Fermi level, as compared to that of RuO2 alone, leading to improved intrinsic electrocatalytic activity towards these important reactions. These results demonstrate the significance of Mott-Schottky heterojunctions in the development of high-efficiency electrocatalysts for various new energy technologies.

Boosting 2e− Oxygen Reduction Reaction in Garland Carbon Nitride With Carbon Defects for High-efficient Photocatalysis-self-Fenton Degradation of 2,4-Dichlorophenol

Abstract: Photocatalytic two-electron oxygen reduction reaction (2e - ORR) has been regarded as a promising strategy to solve the disadvantage of Fenton technology (constant addition of H 2 O 2 ). Herein, a photocatalysis-self-Fenton system was constructed on garland g-C 3 N 4 with carbon defects (GCN-PSFs) for pollutants degradation. Carbon defects in the obtained GCN not only accelerate charge separation but also improve 2e - ORR. As expected, the apparent rate constant for 2,4-DCP degradation by GCN-PSFs enhances to 0.070 min −1 , which is 5.4, 3.3 and 2.6 times as that of BCN, BCN-PSFs and GCN. The capture experiments and electron spin resonance indicate that the high activity is attributed to abundant ∙OH radicals, which are formed from the in-situ produced H 2 O 2 . Density functional theory (DFT) calculation confirms that the carbon defects in GCN is favorable for photocatalytic 2e - ORR to H 2 O 2 . This work provides a new insight for high-efficient degradation of organic pollutants by PSFs. • A photocatalysis-self-Fenton system was constructed based on garland g-C 3 N 4 . • Carbon defects accelerate charge separation and improve the O 2 adsorption ability. • Carbon defects in the Garland g-C 3 N 4 is favorable for photocatalytic 2e - ORR. • The photocatalysis-self-Fenton system is efficient for 2,4-Dichlorophenol degradation. • Abundant ∙OH radials were produced by efficient utilization of in-situ generated H 2 O 2 .

Promoted self-construction of β-NiOOH in amorphous high entropy electrocatalysts for the oxygen evolution reaction

Abstract: The exploration of an efficient electrocatalyst for the oxygen evolution reaction (OER) is urgently required for sustainable renewable-energy conversion and storage. Due to the increased chemical complexity, multimetallic catalysts provide flexibility to alter their electronic and crystal structure to attain a superior intrinsic catalytic activity via synergistic effects, which is seldom accomplished using single metal catalysts. However, the high chemical complexity increases the difficulty to prepare elemental homogenous catalysts and reveal their synergistic effect during OER process, which further hinder the design of multimetallic catalysts. Here, high entropy concept is utilized to design an NiFeCoMnAl oxide with amorphous structure as OER catalyst. The direct evidence of active Ni sites is provided by the operando Raman measurements and Fe can modify oxygen intermediates binding energy on Ni sites. The X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) reveal that the incorporation of Mn can construct the electron-rich environment of active Ni center, and the relatively lower oxidation state of Ni facilitates the self-construction of β-NiOOH intermediates, which shows promoted OER activity as confirmed by density functional theory calculations. Doping Co can enhance the conductivity and doping Al leads to the formation of nanoporous structure through dealloying process, thus each component is essential for improving OER performance. The optimized NiFeCoMnAl catalyst exhibits an overpotential of 190 mV at 10 mA cm−2 in 1 M KOH solution, much superior to the ternary and quaternary counterparts. This work sheds light on understanding the origin of high entropy catalysts’ OER activity and thereby enables the rational design of multinary transition metallic catalysts.

Highly reactive Cu-Pt bimetallic 3D-electrocatalyst for selective nitrate reduction to ammonia

Abstract: Identifying electrocatalytic materials that generate fossil-free ammonia through N-recycling from polluted water sources is required. Bimetallic Cu-Pt foam electrodes were synthesized to enhance electrochemical reduction of nitrate (ERN) by the introduction of bimetallic catalytic sites. Electrodes were benchmarked against Cu foam using engineering figures of merit. Cu-Pt (180 s) electrode achieved 94% conversion of NO3--N in 120 min yielding 194.4 mg NH3- N L-1 gcat-1, with a selectivity towards ammonia (SNH3) of 84% and an electrical energy per order decrease by ~70% respect pristine Cu foam. Bimetallic electrodes with low Pt loadings (<0.50 wt%) demonstrated that synergistic effects of Cu-Pt nanointerfaces enabled hybridized mechanisms of catalytic electrochemical and hydrogenation reduction processes. These encouraging outcomes emphasize the potential of Cu-Pt foam electrodes to treat contaminated water sources with nitrate, while allowing a sustainable decentralized ammonia recovery. Enriched water for crops irrigation can therefore be a prospect use for this added value product.

Ball milling-assisted preparation of N-doped biochar loaded with ferrous sulfide as persulfate activator for phenol degradation: Multiple active sites-triggered radical/non-radical mechanism

Abstract: Designing Fe-carbon catalyst with multiple active sites for persulfate (PS) activation to water purification is challenging. Herein, nitrogen-doped biochar (NBC) loaded with ferrous sulfide (FeS) was synthesized via two-step ball milling. In FeS@NBC BM /PS system, both electron transfer process and reactive oxygen species (ROSs) including SO 4 ⋅ − , O ⋅ H , O 2 • − and 1 O 2 contributed to phenol degradation. Surface-bound S(II) not only interacted with PS for generating SO 4 • − , but also accelerated Fe(III)/Fe(II) circulation by reducing Fe(III). NBC was favorable for phenol adsorption and exposure of oxygen-containing groups, graphitic and pyridinic N active sites, which mediated electron transfer or ROSs formation. Owing to multiple active sites, this system fast achieved almost complete phenol degradation with excellent adaptability to wide pH range of 3–9, high anti-interference capacity to coexisting substances, and was efficient to various water matrices. Furthermore, phenol degradation pathways were elucidated by DFT calculations with intermediate products showing lower toxicity, demonstrating great potentials of proposed system. • Ball-milled N-doped biochar-supported FeS is synthesized for persulfate activation. • FeS@NBC BM shows 27.7 and 9.88-fold catalytic activity compared to NBC BM and FeS@BC. • Surface-bound S(II) participates in SO 4 • − formation and promotes Fe(III)/Fe(II) cycle. • Graphitic/pyridinic N mediate electron transfer or nucleophilic addition of PS. • Both radical and non-radical pathways are involved in phenol degradation process.

Unique g-C3N4/PDI-g-C3N4 homojunction with synergistic piezo-photocatalytic effect for aquatic contaminant control and H2O2 generation under visible light

Abstract: Herein, a g-C3N4/PDI-g-C3N4 homojunction has been fabricated for piezo-photocatalytic atrazine removal and exhibited better performance than individual photocatalysis or piezocatalysis. The introduction of PDI induces the π-π interaction facilitating electrons migration, and twists the g-C3N4 plane into a more polar porous structure with enhanced piezoelectricity. The homojunction facilitates the photoelectron transfer at the g-C3N4/PDI-g-C3N4 interfaces. The photoelectricity and the piezoelectricity of g-C3N4/PDI-g-C3N4 were assessed. The finite element simulation showed that the porous structure of the g-C3N4/PDI-g-C3N4 is essential to the enhanced piezoelectricity. Astonishingly, the piezo-photocatalytic atrazine degradation rate under an optimized condition (pH=2.97) reached 94% within 60 minutes. Moreover, the g-C3N4/PDI-g-C3N4 homojunction produced 625.54 μM H2O2 during the one-hour piezo-photocatalysis. Given the quenching experiments, reactive species detection and the electronic band of g-C3N4/PDI-g-C3N4, the piezo-photocatalytic mechanism has been proposed. In addition, the degradation pathways and the reduced intermediates toxicity intermediates of atrazine have been investigated.

Unique g-C3N4/PDI-g-C3N4 homojunction with synergistic piezo-photocatalytic effect for aquatic contaminant control and H2O2 generation under visible light

Abstract: Herein, a g-C 3 N 4 /PDI-g-C 3 N 4 homojunction has been fabricated for piezo-photocatalytic atrazine removal and exhibited better performance than individual photocatalysis or piezocatalysis. The introduction of PDI induces the π-π interaction facilitating electrons migration, and twists the g-C 3 N 4 plane into a more polar porous structure with enhanced piezoelectricity. The homojunction facilitates the photoelectron transfer at the g-C 3 N 4 /PDI-g-C 3 N 4 interfaces. The photoelectricity and the piezoelectricity of g-C 3 N 4 /PDI-g-C 3 N 4 were assessed. The finite element simulation showed that the porous structure of the g-C 3 N 4 /PDI-g-C 3 N 4 is essential to the enhanced piezoelectricity. Astonishingly, the piezo-photocatalytic atrazine degradation rate under an optimized condition (pH=2.97) reached 94% within 60 min. Moreover, the g-C 3 N 4 /PDI-g-C 3 N 4 homojunction produced 625.54 μM H 2 O 2 during the one-hour piezo-photocatalysis. Given the quenching experiments, reactive species detection and the electronic band of g-C 3 N 4 /PDI-g-C 3 N 4 , the piezo-photocatalytic mechanism has been proposed. In addition, the degradation pathways and the reduced intermediates toxicity intermediates of atrazine have been investigated. • Unique g-C 3 N 4 /PDI-g-C 3 N 4 (CNPC) homojunction have been fabricated. • CNPC showed superior piezo-photocatalytic atrazine removal and H 2 O 2 generation. • The π-π stacked CNPC homojunction facilitated the charge transfer. • The enhanced polarity of CNPC is responsible for the piezoelectricity increases. • The results indicated the reduced toxicity of intermediates in the system.

Self-supported bimetallic phosphides with artificial heterointerfaces for enhanced electrochemical water splitting

Abstract: Rational design and exploitation of efficient and inexpensive catalysts for water electrolysis are highly desired, yet very challenging. Herein, for the first time, we report a nanostructured catalyst of nickel phosphides-ruthenium phosphides self-supported on nickel foam (Ni 2 P-Ru 2 P/NF) through an in situ growth-phosphorization process. As expected, by virtue of prominent intrinsic activity, rich electrochemically active sites, and high electronic conductivity, the resultant Ni 2 P-Ru 2 P/NF exhibits enhanced electrocatalytic behavior for the oxygen evolution reaction and hydrogen evolution reaction, which delivers low overpotentials of 160 and 101 mV at 10 mA cm 2 in alkaline media, respectively. Remarkably, the Ni 2 P-Ru 2 P/NF can dramatically accelerate full water splitting with an ultralow cell voltage of 1.45 V at 10 mA cm −2 , which far exceeds the benchmark Pt-C/NF//RuO 2 /NF (1.64 V) and ranks among the best electrocatalysts previously reported. A high-efficiency bifunctional electrocatalyst for the oxygen evolution reaction and hydrogen evolution reaction was designed by constructing the Ni 2 P-Ru 2 P heterointerfaces on nickel foam. Impressively, the resultant catalyst exhibits outstanding catalytic performance toward overall water splitting. • Self-supported Ni 2 P-Ru 2 P/NF with abundant artificial heterointerfaces is successfully synthesized in situ. • Unique 3D architectures with superhydrophilicity provide large surface area and rich exposed sites. • Ni 2 P-Ru 2 P/NF shows enhanced catalytic performance for OER and HER. • An ultralow cell voltage (1.45 V) and about 100% Faradaic yield toward over water splitting.

Facile synthesis of MoP-Ru2P on porous N, P co-doped carbon for efficiently electrocatalytic hydrogen evolution reaction in full pH range

Abstract: Developing efficient, novel and pH-universal electrocatalysts toward hydrogen evolution reaction (HER) is a challenging and meaningful task for the large-scale and practical hydrogen application via electrocatalytic overall water-splitting. Herein, we propose one-pot strategy to prepare MoP and Ru2P nanoparticles supported on N, P co-doped carbon (MoP-Ru2P/NPC) with porous nanostructures. Benefiting from overly specific characters, the synthetical MoP-Ru2P/NPC displays low overpotentials of 47 mV, 126 mV and 82 mV to obtain 10 mA cm−2 in alkaline, neutral and acid electrolytes as well as remarkable stability. Moreover, a low cell voltage (1.49 V) is required to spur 10 mA cm−2 for full water-splitting in 1 M KOH with the MoP-Ru2P/NPC and commercial NiFe foam as the cathode and anode, respectively. Remarkably, the intermittent sustainable energies, including wind, solar and thermal energies, can drive hydrogen generation directly and then stored them accordingly.

Facile synthesis of MoP-Ru2P on porous N, P co-doped carbon for efficiently electrocatalytic hydrogen evolution reaction in full pH range

Abstract: Developing efficient, novel and pH-universal electrocatalysts toward hydrogen evolution reaction (HER) is a challenging and meaningful task for the large-scale and practical hydrogen application via electrocatalytic overall water-splitting. Herein, we propose one-pot strategy to prepare MoP and Ru2P nanoparticles supported on N, P co-doped carbon (MoP-Ru2P/NPC) with porous nanostructures. Benefiting from overly specific characters, the synthetical MoP-Ru2P/NPC displays low overpotentials of 47 mV, 126 mV and 82 mV to obtain 10 mA cm-2 in alkaline, neutral and acid electrolytes as well as remarkable stability. Moreover, a low cell voltage (1.49 V) is required to spur 10 mA cm-2 for full water-splitting in 1 M KOH with the MoP-Ru2P/NPC and commercial NiFe foam as the cathode and anode, respectively. Remarkably, the intermittent sustainable energies, including wind, solar and thermal energies, can drive hydrogen generation directly and then stored them accordingly.

Enhancement of persulfate activation by Fe-biochar composites: Synergism of Fe and N-doped biochar

Abstract: Persulfate-based (PS-based) advanced oxidation process is a promising technology for degradation of organic pollutants. PS activation needs efficient and economical catalysts and heterogeneous Fe-carbon composites are competitive. Herein, novel N-doped biochar-loaded nanoscale zero-valent iron (nZVI) composites (Fe@N-BC) were synthesized and evaluated for PS activation. Detailed characterization data indicated that graphitic and pyridine N structures were introduced by N-doping, which enhanced the anchoring, dispersion and loading of amorphous nZVI on biochar. Remarkably, the optimized Fe@N-BC material, Fe@N2-BC900, presented excellent catalytic performance for PS activation for lindane removal. The N-doped defects in biochar acted as reactive bridges and accelerated the electron transfer between nZVI and PS, showing strong synergistic effects toward nZVI. O 2 • − and 1O2 were the dominant active species in catalytic systems. Additionally, Fe@N2-BC900 catalyst showed effectiveness over a wide pH range for lindane removal. This work provides a new approach to the rational design and application of Fe@N-BC for persulfate activation in pollution control, which is certified by deep exploration of reaction mechanism.

Iron-cation-coordinated cobalt-bridged-selenides nanorods for highly efficient photo/electrochemical water splitting

Abstract: Water-electrolysis intends a favorable green technology to hold the worldwide energy and ecological disaster, but its efficacy is significantly restricted by the slow reaction kinetics of both the anodic oxygen evolution reaction (OER) and cathodic hydrogen evolution reaction (HER). Herein, the fabrication of multi-cation incorporated Fe 2+/3+ /Co 2+ species into selenides nanorods (Fe@Co/Se 2 -NRs) and corresponding analysis of their catalytic activity for electrochemical (EC) and solar-driven water splitting as a purpose of the composition are reported. This efficient approach can fabulously endow electronic structure modulation and the direct evidence of electron-transfer-route between transition-metals and selenides, which are vital to improving the electrocatalytic activity, has never been confirmed before. For the first time, we explored the electron-transfer route of intensely-coupled Fe@Co/Se 2 -NRs catalyst, in which the Fe 2+/3+ /Co 2+ species strongly-coupled to selenide through the Fe-coordinated Co-bridged-bond. Finally, density functional theory calculations disclose that the multi-cation doping effects into selenides are vital for enhanced electrocatalytic performance. • The self-templated approach developed for bifunctional OER/HER electrocatalysts. • Iron-Cation-Coordinated Cobalt-Bridged-Selenides Nanorods structure increases the number of active sites. • The Fe@Co/Se 2 -nanorods reveal superior bifunctional OER/HER performance. • Requires only 1.5 V@10 mA cm −2 for electrochemical and solar-to-hydrogen conversion efficacy of ∼ 7.0% for water splitting. • DFT and XAS analysis exposed the electron-transfer route of intensely coupled Fe@Co/Se 2 -NRs.