Showing papers in "Applied Catalysis B-environmental in 2021"
TL;DR: In this article, a review of the recent processes and advances on catalytic elimination of VOCs over nanoparticles catalysts is presented, and the perspectives to the scientific issues and challenges faced, as well as the future outlooks are proposed.
Abstract: Volatile organic compounds (VOCs) with the properties of volatility, toxicity and diffusivity pose a serious threat to human health and eco-environment. Catalytic oxidation technology has been considered as a highly efficient option for the treatment of VOCs. This review systematically summarizes the recent processes and advances on catalytic elimination of VOCs over nanoparticles catalysts. Firstly, catalytic performances of catalysts for VOC degradation are evaluated and compared on the basis of unified performance metrics. Secondly, catalytic mechanisms of VOC oxidation, based on experimental and theoretical studies, are systematically introduced. Then, catalytic reactors employed in VOC elimination processes are summarized. In particular, photothermocatalysis by integrating (thermo)catalysis with photocatalysis is also elucidated. Lastly, the perspectives to the scientific issues and challenges faced, as well as the future outlooks are proposed. Collectively, this review will provide theoretical and experimental foundation for rational fabrication and application of nanoparticles catalysts toward VOC elimination in future.
299 citations
TL;DR: In this article, a heterogeneous Fenton-like catalysts biochar modified CuO2 (CuFeO2/BC) were fabricated by hydrothermal method without additional chemical reducing agent.
Abstract: The heterogeneous Fenton-like catalysts biochar modified CuFeO2 (CuFeO2/BC) were fabricated by hydrothermal method without additional chemical reducing agent. The systematic characterization demonstrated that higher CuFeO2 particles dispersion and larger BET surface area of CuFeO2/BC catalyst contributed to higher catalytic activity towards the tetracycline (TC) degradation compared to pure-phase CuFeO2. The optimum conditions for TC removal were 598.63 mg L-1 of CuFeO2/BC-1.0, 57.63 mM of H2O2 and pH = 6.27 according to the result of a response surface methodology based on the central composite design. The CuFeO2/BC-1.0 exhibited an excellent reusability and good stability by recycling degradation. The OH was evidenced to the main active radical by scavenging experiments and electron spin resonance. The XPS revealed that the high catalytic efficiency was attributed to the synergistic effect of Fe3+/Fe2+ and Cu2+/Cu+ redox cycles, and the degradation intermediates of TC and toxicity analysis were evaluated.
286 citations
TL;DR: In this article, an efficient single-atom electrocatalyst with Fe-N-C sites embedded in 3D N-doped ordered mesoporous carbon framework has been proposed for oxygen reduction reaction (ORR) in alkaline electrolyte.
Abstract: Single-atom Fe-N-C electrocatalysts have emerged as the most promising oxygen reduction reaction (ORR) catalyst. However, the low Fe loading and inaccessibility of Fe-N-C sites limit the overall ORR activity. Here, we report an efficient single-atom electrocatalyst (Fe-N-C/N-OMC) with Fe-N-C sites embedded in three-dimensional (3D) N-doped ordered mesoporous carbon framework. Fe-N-C/N-OMC shows high half-wave potential, kinetic current density, turnover frequency and mass activity towards ORR in alkaline electrolyte. Experiments and theoretical calculations suggest that the ultra-high ORR activity stems from the boosted intrinsic activity of FeN4 sites by graphitic N dopants, high density of accessible active site generated by high Fe and N loadings and ordered mesoporous carbon structure as well as facilitated mass and electron transport in 3D interconnected pores. Fe-N-C/N-OMC also shows comparable ORR activity to Pt/C in acidic electrolyte. As the cathode for zinc-air battery, Fe-N-C/N-OMC exhibits high open-circuit voltage, high power density and remarkable durability.
282 citations
TL;DR: In this paper, a step-scheme photocatalytic mechanism based on S/Cl-CN/CdSe-D heterostructure was proposed, where the S atom is appropriate to be incorporated into the CN framework to replace N atom, which is beneficial to adjust the band gap.
Abstract: The poor utilization of visible light and the speedy recombination of photoexcited carriers limit the further development of carbon nitride polymer (CN) photocatalysts. It is a valid means for enhancing the photocatalytic ability to ameliorate the electronic and physicochemical properties via modifying the structure of CN. The sulfur- and chlorine-codoped graphite CN (S/Cl-CN) was successfully fabricated with low-cost ammonium chloride and thiourea as precursors. The introduction of Cl atoms will establish interlayer channels to promote interlayer charge migration and up-shifted conduction-band level. S atom is appropriate to be incorporated into the CN framework to replace N atom, which is beneficial to adjust the band gap. Then, inorganic-organic CdSe-diethylenetriamine (D) grown in situ are employed to fabricate a S/Cl-CN/CdSe-D heterojunction. S/Cl-CN/CdSe-D heterojunction exhibits greater hydrogen evolution activity compared to CN, S-CN, Cl-CN, S/Cl-CN, CdSe-D and CN/CdSe-D. Finally, Step-scheme (S-scheme) photocatalytic mechanism based on S/Cl-CN/CdSe-D heterostructure was proposed.
277 citations
TL;DR: In this paper, a simple boron (B) doping of C3N4/ZnO was proposed to switch from the Z-scheme to type II.
Abstract: Heterojunction photocatalysts are very promising for solar hydrogen production due to their high efficiency in photo-driven charge generation and separation. A C3N4/ZnO heterostructure nanocomposite harvests a wide range of solar light from the UV and visible regions and retains a high redox potential due to its Z-scheme band structure. However, since both C3N4 and ZnO have sufficiently high conduction band energies to drive hydrogen photoreduction, a type II heterojunction is more beneficial for enhancing the hydrogen production efficiency in the current system. In this study, we first demonstrated the charge transfer mechanism switching from the Z-scheme to type II by simple boron (B) doping of C3N4/ZnO. The doping of C3N4 with low-electronegativity boron increases its Fermi level by 0.4 V, making it even higher than that of ZnO. As a result, the Fermi level alignment of B-doped C3N4 with ZnO causes a reversed band bending direction at the C3N4/ZnO junction. The resultant charge transfer switching from the Z-scheme (C3N4/ZnO) to type II (B-doped C3N4/ZnO) was confirmed by UPS and ESR analysis. Type II B-doped C3N4/ZnO shows a stable, drastic increase in the photocatalytic hydrogen evolution rate, approximately 2.9 times higher than that of undoped C3N4/ZnO. The decreased bandgap energy of B-doped C3N4/ZnO also contributes to an additional improvement in efficiency through enhanced light harvesting. Our work presents a simple but effective strategy to design highly capable heterojunction photocatalysts via charge transfer switching with a doping method.
275 citations
TL;DR: In this article, the pyridinic N-Co binding in Co3O4@NSC was found to accelerate the formation of HOCl at high level of Cl- in a peroxymonosulfate (PMS) reaction.
Abstract: In this work, Co3O4 embedded nitrogen and sulfur co-doped porous char (Co3O4@NSC) was prepared after one-pot pyrolysis of N, S in-rich rubber powder (RP) to determine the binding relationship between Co nanoparticles and multiple doped heteroatoms. Results indicated pyridinic N was more easily to coordinate with Co3O4 nanoparticles, forming the pyridinic N-Co binding in Co3O4@NSC, which was the dominant catalytic sites for peroxymonosulfate (PMS) activation. Paracetamol (PCM) degradation was greatly facilitated with Cl- surrounding in Co3O4@NSC/PMS system due to the formation of large amounts of HOCl generated from the direct reaction of Cl- with PMS. The Cl↓ serving as a precursor of HOCl by reacting with PMS can be further strengthened by pyridinic N-Co bindings in Co3O4@NSC than the NSC. As a result, the pyridinic Co-N sites not only acted as the essential catalytic sites for PMS activation, but also accelerated the formation of HOCl at high level of Cl-.
262 citations
TL;DR: In this article, ultrathin rhodium-doped nickel iron layered double hydroxide nanosheets are successfully synthesized, which exhibit outstanding hydrogen evolution reaction (HER) and OER performance, and advanced overall water splitting.
Abstract: Water splitting is a green strategy for hydrogen generation but greatly hindered by the sluggish anodic oxygen evolution reaction (OER). Herein, ultrathin rhodium-doped nickel iron layered double hydroxide nanosheets are successfully synthesized, which exhibit outstanding hydrogen evolution reaction (HER) and OER performance, and advanced overall water splitting. More impressively, the remarkable mass activity of 960 mA mg1 at 1.55 V (1.7 times larger than NiFe-LDH) for urea electro-oxidation reaction (UOR) shows the great potential to surmount the sluggish OER for overall water splitting. A urine-mediated electrolysis cell is subsequently configured, delivering a current density of 10 mA cm-2 with a potential of 1.35 V, which is 105 mV lower than that of urea-free counterpart. The enhanced catalytic activity and cell performance are attributed to the introduction of Rh into NiFe-LDH matrix by changing the electronic structure, allowing optimization of the adsorbed species, as confirmed by experimental measurements and computational analyses.
251 citations
TL;DR: In this article, a dual Z-scheme advanced photocatalyst g-C3N4/Bi4Ti3O12)/Bi4O5I2 was proposed for coupled photocatalytic H2 evolution and degradation of antibiotics with high efficiency.
Abstract: Inspired by waste to energy production, we report construction of dual Z-scheme advanced photocatalyst g-C3N4/Bi4Ti3O12/Bi4O5I2 heterojunction for coupled photocatalytic H2 evolution and degradation of antibiotics with high efficiency. The optimal CTBT-30 i.e (40 %g-C3N4/Bi4Ti3O12)/30 % Bi4O5I2 photocatalyst exhibited an excellent rate of H2 production under visible light (56.2 mmol g−1 h−1) along with simultaneous 87.1 % ofloxacin (OFL) removal. The H2 production rate is manifolds higher than in ultrapure water, sulfadiazine, rhodamine B and higher in hole scavenging triethanolamine. The interfacial intimate coupling with well-matched energy bands, foster the charge separation with effective Z-scheme transfer facilitated by I3−/I− and Bi3+/Bi5+ and redox mediators. The scavenging of majority of holes for direct oxidation or via OH radical formation leaves photogenerated electrons (at CB of g-C3N4 and Bi4O5I2) free for H2 evolution from H2O. Such work is promising for designing high photo-absorbing heterojunction photocatalysts for dual functionalities of clean energy production and environmental detoxification.
245 citations
TL;DR: In this article, a series of polydopamine-modified TiO2 hollow spheres were fabricated by in situ self-polymerization of dopamine to systematically investigate the effect of PDA wrapping on the photocatalytic CO2 reduction activities.
Abstract: Photocatalytic CO2 conversion into solar fuels has been a promising strategy to utilize abundant solar energy and alleviate greenhouse effect. Herein, a series of polydopamine-modified TiO2 (TiO2@PDA) hollow spheres were fabricated by in situ self-polymerization of dopamine to systematically investigate the effect of PDA wrapping on the photocatalytic CO2 reduction activities of TiO2. Among all TiO2@PDA composite photocatalysts, the highest value of methane yield (1.50 μmol h−1 g−1) was achieved with 0.5 % PDA, which was 5 times than that of pure TiO2 (0.30 μmol h−1 g−1). The improvement of photocatalytic activity and methane selectivity was ascribed to the enhanced light absorption, promoted CO2 adsorption capacity, increased reduction power of photogenerated electrons, as well as efficient separation and transfer of photogenerated charge carriers induced by the S-scheme heterojunction between TiO2 and PDA. This work provides a facile surface modification method with cost-effective polymer materials in photocatalytic CO2 conversion.
243 citations
TL;DR: In this paper, the evolution of bio-Fe in Enteromorpha during thermal pyrolysis and the role of the derived Fe-N-C in peroxymonosulfate (PMS) activation and organic degradation was revealed.
Abstract: Enteromorpha as a seawater pollutant was innovatively converted into a functional carbocatalyst to driven Fenton-like reactions.After direct pyrolysis of Enteromorpha at 900 °C without additional chemicals, a large number of Fe clusters and single Fe sites are anchored onto N-doped carbon matrixes (Enteromorpha-derived Fe-N-C) with a high Fe loading of 0.84 wt.%. The Enteromorpha-derived Fe-N-C exhibits a high activity in the heterogeneous activation of peroxymonosulfate (PMS) for organic pollutant degradation. Radical quenching experiments and electrochemical analysis tests verify the nonradical oxidation by high-valence iron-oxo species and an electron-transfer pathway. The single Fe atoms, which only accounted for the minority of the Fe species in Fe-N-C, acted as the dominated reactive sites for the formation of highly oxidizing FeIV=O and FeV=O sites. This work unveils the evolution of bio-Fe in Enteromorpha during thermal pyrolysis and the role of the derived Fe-N-C in PMS activation and organic degradation.
237 citations
TL;DR: In this article, the synergistic effects of photocatalytic activations of peroxydisulfate (PDS) via the direct electron transfer PDS activation over P25M175 and indirect electron transfer PS activation over pristine MIL-88A were investigated.
Abstract: PDINH/MIL-88A(Fe) composites (PxMy) were fabricated from MIL-88A(Fe) and perylene-34,910-tetracarboxylic diimide (PDINH) via facile ball-milling strategy. The optimum P25M175 exhibited outstanding degradation performance toward chloroquine phosphate (CQ) by activating peroxydisulfate (PDS) under low power LED visible light. The synergistic effects of photocatalytic activations of PDS via the direct electron transfer PDS activation over P25M175 and indirect electron transfer PDS activation over pristine MIL-88A contributed to the boosted CQ degradation efficiency. The active species capture experimental data and electron spin resonance (ESR) determinations revealed that both active radicals (like SO4−, OH, O2−, h+) and nonradical singlet oxygen (1O2) participated in the CQ decomposition. The CQ degradation pathways and the toxicity evaluation of the intermediates were proposed based on LC–MS determination and DFT calculation. Also, P25M175 demonstrated good reusability and stability. The findings within this work offered deep insights into the mechanisms of organic pollutants degradation via photocatalysis-activated SR-AOP over Fe-MOF photocatalyst.
TL;DR: Li et al. as mentioned in this paper designed the shell-thickness-controlled Ni3C@Ni/g-C3N4 photocatalysts with intimate Schottky-junctions by an in situ high-temperature transformation strategy.
Abstract: Herein, we designed the shell-thickness-controlled Ni3C@Ni/g-C3N4 photocatalysts with intimate Schottky-junctions by an in situ high-temperature transformation strategy. Meanwhile, we found that the cocatalysts with optimized Ni shell-layer thickness of 15 nm could achieve the best visible-light photocatalytic H2-production performance of 11.28 μmolh−1, with an apparent quantum yield (AQY) of 1.49 % at 420 nm, which was 16 times higher than that of Ni3C/g-C3N4. Moreover, an excellent stability is achieved. The well-defined density functional theory (DFT) calculations indicate that the “TOP_C1” sites of Ni3C@Ni can exhibit the H adsorption and Gibbs free energies of -0.07eV and 0.18 eV, respectively, which should be hydrogen-evolution active sites instead of two “HOLLOW” sites. Interestingly, the intimate Schottky-junctions, could hinder rapid charge recombination, increase reactive sites, boost catalytic kinetics and passivate unstable surface of Ni3C, thus achieving shell-thickness-dependent hydrogen evolution. Therefore, the Ni3C@Ni core–shell cocatalysts will open a new avenue for robust solar fuel production.
TL;DR: In this article, a Z-scheme 2D/2D α-Fe2O3/g-C3N4 heterojunction was constructed using an impregnation-hydrothermal method.
Abstract: Heterojunctions have attracted considerable attention for efficiently utilizing solar energy and improving conversion efficiency during pollutant degradation. Herein, carbon nitride and hematite (α-Fe2O3) are used to prepare a Z-scheme 2D/2D α-Fe2O3/g-C3N4 heterojunction using an impregnation-hydrothermal method. The unique 2D/2D structure has a high interfacial area and widely-dispersed active sites. The energy band structure of the Z-scheme heterojunction leads to broad visible-light absorption and promotes charge transfer. Optimizing the content of the α-Fe2O3 precursor in composite leads to a maximum efficiency of 60.8% for the removal of 600 ppb of NO, which is approximately 1.78 times that of g-C3N4 (34.2%). The photocatalytic performance is greatly promoted because of the formation of the heterojunction and the strong interfacial action between g-C3N4 nanosheets and α-Fe2O3 nanoplates. Cycling experiments verify that the α-Fe2O3/g-C3N4 heterojunction has good stability and reusability. The α-Fe2O3/g-C3N4 heterojunction therefore has great potential in sustainable and efficient pollutant degradation.
TL;DR: In this article, high-efficient N-doped carbon materials were prepared by direct carbonization of polyaniline (PANI) at 700 °C-1000 °C.
Abstract: N-doped carbonaceous materials are promising efficient catalysts for peroxymonosulfate (PMS) activation In this study, the high-efficient N-doped carbon materials were prepared by direct carbonization of polyaniline (PANI) at 700 °C–1000 °C It was optimized that the CPANI-9 (carbonized polyaniline prepared at 900 °C) exhibited excellent catalytic performance to activate PMS for phenol degradation, which was efficient over a wide pH range (pH 35∼9) In the CPANI-9/PMS system, the PMS adsorption/activation was identified as the key step determining the reaction rate The quenching experiments and electron paramagnetic resonance demonstrated that the non-radical pathway was dominant in phenol degradation and singlet oxygen (1O2) was the main active specie Graphitic N, pyridinic N, defects and ketonic groups (C O) were identified as catalytic sites Interestingly, only the presence of PO43− greatly decreased the phenol degradation rate and PMS decomposition The CPANI-9/PMS system could also degrade effectively various organic pollutants, indicating that it had potential practical application
TL;DR: In this paper, the degradation rate constant and TOC removal efficiency of TC−HCl in 120 min over the Co/V-g-C3N4-2 sample run up to 4.00 and 2.45 times as much as that of g-C 3N4, respectively.
Abstract: The photocatalytic activity of bimetallic co-doped g-C3N4 can be boosted dramatically, whereas the enhanced mechanisms essentially have been rarely revealed. Here, the prepared Co/V co-doped g-C3N4 significantly enhances the photocatalytic activity. The degradation rate constant and TOC removal efficiency of TC−HCl in 120 min over the Co/V-g-C3N4-2 sample run up to 4.00 and 2.45 times as much as that of g-C3N4, respectively. The outstanding photocatalytic performance is attributed to the improved charge separation efficiency and visible-light harvest ability. The density functional theory (DFT) investigations reveal the incorporation of Co/V into g-C3N4 can induce the bimetallic synergetic regulating effect on electronic structure, which results in improving the physical, optical and photoelectrochemical properties. Moreover, the significant degradation intermediates, pathway and mechanism of TC−HCl, and charge transfer behaviors are also discussed in depth. This work provides a meritorious instance to design and synthesize new bimetallic co-doped g-C3N4 materials in the photocatalytic application field.
TL;DR: In this paper, a rod-like MnCeOx was synthesized by pyrolyzing Mn/Ce-BTC for toluene oxidation, and the 3Mn2Ce catalyst exhibits superior catalytic performance and stability under high humidity (10 % H2O).
Abstract: Herein, a series of rod-like MnCeOx are synthesized by pyrolyzing Mn/Ce-BTC for toluene oxidation. The 3Mn2Ce catalyst exhibits superior catalytic performance and stability under high humidity (10 % H2O). XRD, Raman, H2-TPR, O2-TPD, XPS and EXAFS results confirm that the formation of solid solution between Ce and Mn species and better reducibility play a key role in toluene oxidation. H2O-TPD, toluene-TPD, toluene-TPSR, in situ DRIFTS in different conditions and TD-GC–MS confirm that the introduction of water can promote toluene mineralization. H2O-TPD indicates that oxygen vacancies adsorbed H2O to provide HOH active sites and promote the conversion of Oads to Olatt. The degradation pathway of toluene was toluene→benzaldehyde→benzoate→CO2 and H2O. Additionally, the water promotion is also confirmed by DFT calculations. The promotion of water vapor is that the water vapor is conducive to the adsorption of toluene, benzaldehyde and oxygen, and promotes the activation of oxygen.
TL;DR: In this paper, nitrogen doped g-C3N4 (NCN) with the extremely narrow band gap was prepared and applied for the photodegradation of phenols, which enhanced the absorption of visible light and further promoted the photocatalytic activity.
Abstract: In this work, nitrogen doped g-C3N4 (NCN) with the extremely narrow band gap was prepared and applied for the photodegradation of phenols. Experiments and DFT (the density functional theory) computation identified that N-doping introduced in the g-C3N4 matrix by substituting C atoms. DFT, PL (photoluminescence) spectra, optical property characteristic and PEC (photoelectrochemical) indicated that NCN possess extremely narrow band gap, efficient photogenerated carrier separation and the charge transfer, which enhanced the absorption of visible light and further promoted the photocatalytic activity. As a result, NCN(2:2) showed about twice higher photodegradation efficiencies and 3 times rate constant than pristine g-C3N4. The radical trapping experiments showed that •O2- radical and h+ served as crucial active species during the whole photodegradation reaction. This work can provide a strategy to enhance the photocatalytic activity of photocatalysts via introduce foreign atoms in matrix.
TL;DR: In this paper, a hierarchical structure ZnIn2S4@PCN-224 via a solvothermal method is employed to establish a novel hierarchical structured ZnS4-based photocatalysis, which has a hydrogen production rate of 0.284 mmol h−1.
Abstract: As a typical member of sulfide family, ZnIn2S4 bears impressive activity in photocatalysis. Nonetheless, egregious recombination of photo-excited electron and hole pairs confines its practical usage. In this study, PCN-224, a metal organic framework (MOF) composed of porphyrin linkers and Zr clusters, is employed to establish a novel hierarchical structured ZnIn2S4@PCN-224 via a solvothermal method. These as-prepared composites are further evaluated by visible-light-driven photocatalysis and able to present steady performance. The optimized ZnIn2S4@PCN-224 has a hydrogen production rate of 0.284 mmol h−1 in absence of Pt, higher than many contrastive ZnIn2S4-based photocatalysts even in assistance of Pt cocatalyst. Besides, it is able to dominate the degradation of tetracycline hydrochloride (TCH), giving 99.9 % pollutant removal within 60 min, about 4.7 times higher than that catalyzed by ZnIn2S4. It is supposed that the great improvement in photocatalysis is ascribable to the establishment of Z-scheme junction between ZnIn2S4 and PCN-224.
TL;DR: In this article, the edge decoration effect of pyridine rings on carbon nitride (CN) has been investigated and shown to improve the photocatalytic HER rate of 2AP-CN-15.
Abstract: Intramolecular doping of conjugated nitrogen heterocycles in carbon nitride (CN) has been used to promote charge separation, but it also causes recombination of photogenerated electrons and holes due to their in-plane non-directional transfer. Herein, it achieves the dual regulation of adjusting electron hybridization structure and electron directional transfer from centre to edge of CN by grafting pyridine rings on the edge of CN framework, which effectively drives separation and avoids recombination of photogenerated carriers in plane. The photocatalytic HER rate of up to 6317.5 μmol g−1 h−1 is obtained over the optimum 2AP-CN-15 sample, which has 3.9-fold increase over primal CN. Moreover, the apparent quantum efficiency of HER reaches up to 20.1 % at 420 nm. This work performs an essential insight into edge decoration effect of pyridine rings on CN, which affords a new guidance for the modification of CN-like materials with conjugated nitrogen heterocycles for high-efficiency photocatalytic application.
TL;DR: In this paper, a facile one-pot pyrolytic strategy was employed to fabricate a nitrogen coordinated Co single-atom catalyst (SA Co-N/C catalyst) by using lignin as carbon sources.
Abstract: In this work, a facile one-pot pyrolytic strategy was employed to fabricate a nitrogen coordinated Co single-atom catalyst (SA Co-N/C catalyst) by using lignin as carbon sources. The HAADF-STEM images and X-ray absorption spectra (XAS) analysis showed the isolated Co atoms less than 2 A throughout the entire SA Co-N/C architecture. Results showed that the single-atom Co sites served as the main active sites for naproxen (NPX) degradation via peroxymonosulfate (PMS) activation. This was confirmed by the high positive correlation (R2 = 0.9675) between the rate constants and Co amounts in all SA Co-N/C catalysts. In particular, the as-prepared SA Co-N/C catalyst with a very small Co loading (2.45 wt.%) exhibited exceptional high turnover frequency (TOF) value for NPX (4.82 min−1), which is promising for the potential application prospect. Electron transfer was induced by the single-atom Co sites, which was the dominated mechanism for the NPX degradation.
TL;DR: In this paper, a lead-free halide perovskite Z-scheme and type-II photocatalytic systems for the regulation products selectivity of CO2 reduction reaction are presented.
Abstract: Solar-energy-driven CO2 conversion into value-added chemical fuels holds great potential renewable energy generation. However, most of the photocatalysts facilitate a two-electron reduction process producing CO, hard for the eight-electron CH4 production pathways which can stockpile more solar energy for further utilization. Herein, we developed an in situ assembly strategy to fabricate the lead-free perovskite Cs2AgBiBr6@g-C3N4 Z-scheme system in toluene and the Cs2AgBiBr6@g-C3N4 type-II heterojunction structure in CH2Cl2. By combining the reducing ability of the conduction band of g-C3N4 and the oxidizing ability of the valence band of Cs2AgBiBr6 perovskite, this Z-scheme system exhibits superior CH4 production in photocatalytic CO2 reduction, in contrast to the high CO selectivity for the heterojunction photocatalysts, which is 10-fold and 16-fold higher than that of pure g-C3N4 and pure CABB, respectively. The stability (four consecutive photocatalytic cycles in solvent methanol as sacrificial reagent without obvious decrease of efficiency) and the mechanism (the prominent activity and the high CH4 production selectivity boosted by Z-scheme system) were demonstrated. In this work, the first report for constructing lead-free halide perovskite Z-scheme and type-II photocatalytic systems for the regulation products selectivity of CO2 reduction reaction provides a promising strategy for the fabrication other types of inorganic/organic heterojunction systems.
TL;DR: In this paper, a facile strategy is developed to synthesize M (M = Fe, Cu, Zn, Mo) doped bimetallic sulfide heterostructure Ni3S2/Co3S4 electrocatalysts.
Abstract: Rational design of low-cost and efficient electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is imperative for renewable energy conversion. Herein, for the first time, a facile strategy is developed to synthesize M (M = Fe, Cu, Zn, Mo) doped bimetallic sulfide heterostructure Ni3S2/Co3S4 electrocatalysts. The as-prepared bifunctional Cu-Ni3S2/Co3S4 electrode exhibits excellent electrocatalytic activity for HER and OER in 1 M KOH electrolyte, and it requires only an overpotential of 79 mV (150 mV) to deliver 10 mA cm−2 (20 mA cm-2) current density for HER process. Moreover, it shows a considerable low cell voltage of 1.49 V at the current density of 10 mA cm-2 in a two-electrode configuration which is far surpassing most of the reported bifunctional metal sulfides. Meanwhile, besides increasing the specific surface area of the electrocatalyst by optimizing the microstructure, the introduction of Cu cation could also stimulate the formation of high-valent Ni/Co sites, which can be verified by XPS technique. Density function theory calculations demonstrate that the Cu-doping boosts the formation of high valent Co sites and enhances the charge transfer performance of Ni and Co species, thus promotes intrinsic catalytic activity through modulating the d-band center of Co and reducing the adsorption energy of H and O-containing intermediates (H*, OH*, OOH*) on the surface of the catalyst. This work suggests the importance of exploitation of transition metal ion-doping for promoting the electrocatalytic activity of bimetallic sulfides.
TL;DR: In this paper, a new type of photocatalysts, Au nanodots@thiol-UiO-66@ZnIn2S4 nanosheets (Au@UiOS@ZIS), is elaborately designed for the photocatallytic H2 evolution from water splitting, where Au nano-nodots (NDs) are anchored in the pore space of thiol-functionalized UiO66 metal-organic framework (MOF).
Abstract: Herein, a new type of photocatalysts, Au nanodots@thiol-UiO-66@ZnIn2S4 nanosheets (Au@UiOS@ZIS), is elaborately designed for the photocatalytic H2 evolution from water splitting, where Au nanodots (NDs) are anchored in the pore space of thiol-functionalized UiO66 metal-organic framework (MOF) and ZnIn2S4 nanosheets are wrapped around the UiO66 MOF containing Au NDs. It is found that the different Au positions have a grateful effect on the transfer of photogenerated charge carriers. In Au@UiOS@ZIS, the photoexcited electrons transfers from ZnIn2S4 to UiOS and then to Au NDs, establishing a smooth transmission channel of electrons. As expected, the optimal sample (Au4@UiOS@ZIS40) presents a high photocatalytic H2 production rate of 391.6 μmol/h (10 mg of catalyst) under visible light irradiation, which is 435.1, 61.2 and 10.2 times higher than that of the pure UiOS, ZnIn2S4 and UiOS@ZIS, respectively.
TL;DR: In this article, both CuO nanoparticles and ZnO nanorods were anchored on thermally-exfoliated g-C3N4 nanosheets via isoelectric point-mediated annealing process as a novel nano-photocatalyst towards degradation of amoxicillin (AMOX).
Abstract: In this study, both CuO nanoparticles and ZnO nanorods were anchored on thermally-exfoliated g-C3N4 nanosheets (denoted as CZ@T-GCN) via isoelectric point-mediated annealing process as a novel nano-photocatalyst towards degradation of amoxicillin (AMOX). The features of prepared materials were characterized using BET, UV–vis DRS, XRD, FT-IR, XPS, FE-SEM, TEM, EIS and transient photocurrent techniques. These analyses demonstrated the successful formation of heterojunctions between components of CZ@T-GCN nanocomposite, which reflected in significantly increased electron-hole separation and enhanced degradation of AMOX as compared with pure substances. The investigation of influential operative parameters confirmed that the complete removal of AMOX could be attained under catalytic dosage of 0.9 g L−1 and pH of 7.0 within 120 min simulated sunlight illumination. Generation of OH upon illumination of catalysts was verified by terephthalic acid photoluminescence (TPA-PL) spectroscopy. Also, trapping tests proved that OH and O2 − were the major reactive radicals in AMOX decontamination. A novel double Z-scheme mechanism as well as a tentative pathway for fractionation of AMOX by CZ@T-GCN photocatalytic system were proposed in details. Only a marginal decrease in photocatalytic activity occurred after 5 consecutive tests. In an attempt to study the industrial applicability of catalyst, more than 79 % COD and 63 % TOC were eliminated under optimum conditions during 120 min illumination and the biodegradability of treated wastewater was also improved.
TL;DR: In this paper, a hybrid catalyst CdS/Ag2S/NiS is synthesized via hydrothermal and photodeposition methods, which shows a drastically elevated hydrogen production rate of 48.3 mmol g−1 h−1 under visible light.
Abstract: Cocatalysts play an indispensable role in photocatalytic H2 production via water splitting for the conversion of solar energy into storable chemical energy. Herein, the hybrid catalyst CdS/Ag2S/NiS is synthesized via hydrothermal and photodeposition methods. CdS/Ag2S/NiS shows a drastically elevated hydrogen production rate of 48.3 mmol g−1 h−1 under visible light due to the combined merits of the Schottky junction between CdS and metal-like Ag2S and the constructed p–n junction between CdS and NiS. Time-resolved photoluminescence spectroscopy and photochemical tests reveal the accelerated charge transfer and significantly reduced electron–hole pair recombination. Further investigation with in-situ surface photovoltage imaging technology demonstrates that the reduction cocatalyst Ag2S and oxidation cocatalyst NiS can serve as photogenerated electron and hole traps, respectively. This research not only provides insight into designing high-efficiency photocatalyst for hydrogen production but also utilize a brand new method for the confirmation of charge–carrier migration pathways.
TL;DR: In this article, a simple one-step sulfur doping method is proposed on the basis of exfoliated C3N4 nanosheet, which can directly regulate the band structure of g-C 3N4 and enhance its optical absorption ability.
Abstract: Exfoliating g-C3N4 into 2D nanosheet to minimize the stacking layer for the improvement of charge transfer and separation is considered to be the effective measure to enhance its photocatalytic performance. However, no matter what method is used, the exfoliated g-C3N4 nanosheet shows decreased optical absorption compared to the pristine bulk-like one. In this work, a simple one-step sulfur doping method is proposed on the basis of exfoliated g-C3N4 nanosheet, which can directly regulate the band structure of g-C3N4 and enhance its optical absorption ability. The proposed sulfur doping method redshift the light absorption edge of g-C3N4 nanosheet to the level of pristine bulk-like g-C3N4, and even induce the generation of a new n→π* absorption band. In addition, the introduced sulfur doping site can form a local electron accumulation point, so that to further improve the charge separation efficiency and surface charge transfer ability of g-C3N4 nanosheets.
TL;DR: In this paper, a 3-ZAC micro-needles film was used for the photoreduction of CO2 into CO under UV-vis light irradiation, which has the excellent photocatalytic performance and reusability.
Abstract: Local Surface Plasma Resonance (LSPR) effect enhanced Z-scheme ZnO/Au/g-C3N4 micro-needles film (3-ZAC) has been prepared for the photoreduction of CO2 into CO under UV–vis light irradiation. Photoreduction experiments show that 3-ZAC has the excellent photocatalytic performance and reusability. The CO production can be achieved 689.7 μmol/m2 after 8 h reaction time, which is 4.5 higher than that of the pure ZnO film. 13C isotope test shows that CO is produced from CO2 by photoreduction. DFT calculations confirm that build-in electric field formed at g-C3N4/ZnO interface effectively promoted the electron transfer efficiency in Z-scheme interface. FDTD simulations prove that Au NPs not only act as electron-transfer bridge, but also as LSPR excited source to speed up the separation of electron-hole pairs. In-situ FTIR technique was used to investigate the CO2 photoreduction process. The above characteristics together maximize the electron transfer efficiency, which causes the material has enhanced photocatalytic performance.
TL;DR: MoSe2@Bi2S3/CdS is designed by solvothermal-hydrothermal strategy as discussed by the authors, which conforms to the characteristics of multi-channel charge transfer which favor the spatial separation of carriers.
Abstract: Inadequate separation of carriers is still major obstacles to the practical application of photocatalysis. The reasonable design of semiconductor photocatalysts is expected to break through this bottleneck. Herein, MoSe2@Bi2S3/CdS is designed by solvothermal-hydrothermal strategy. Thanks to the dual Z-Scheme heterojunction conforms to the characteristics of multi-channel charge transfer which favor the spatial separation of carriers. MoSe2@Bi2S3/CdS hollow structure increases the utilization rate of light source, the core-shell structure increases the interface area and the active sites. Moreover, full spectrum absorption endues MoSe2@Bi2S3/CdS with unpredictable photothermal effect, which can touch off near-field temperature rise to facilitate photocatalytic process. Profiting from the synergistic facilitation effect, MoSe2@Bi2S3/CdS exhibits excellent photocatalytic activity in the hydrogen evolution and pollutants removal of Cr (VI) and 2,4,6-trichlorophenol (TCP), which are up to 11.84 mmol/g/h, 98.7% and 99.2%, respectively. This dual functional MoSe2@Bi2S3/CdS photocatalyst may paves new opportunities for solving the energy crisis and environmental pollution.
TL;DR: CeTiOx with nanotube structure was used for selective catalytic reduction with NH3 (NH3-SCR) to remove NOx as mentioned in this paper, in which more than 98 % NO conversion can be achieved in the range of 180−390°C with 100 % N2 selectivity.
Abstract: Cerium and titanium oxides are considered as promising alternative catalysts for selective catalytic reduction with NH3 (NH3-SCR) to remove NOx. However, the poor SO2 or H2O tolerance and stability limit their practical applications. Herein, CeTiOx with nanotube structure (CeTiOx-T) was prepared by hydrothermal method and used for NH3-SCR reaction. CeTiOx-T shows the excellent catalytic activity, SO2 and H2O tolerance and stability, in which more than 98 % NO conversion can be achieved in the range of 180−390 °C with 100 % N2 selectivity. The characterizations verify that CeTiOx-T exhibits amorphous structure due to the strong interaction between Ce and Ti to form short-range ordered Ce-O-Ti species. As results, CeTiOx-T displays the larger BET surface area, more surface Bronsted acid amounts and chemisorbed oxygen, leading to its higher NH3-SCR performance. In situ DRIFTS results suggest the SCR reaction mainly follow L-H and E-R mechanisms at low and high temperature for over CeTiOx-T, respectively.
TL;DR: In this article, a hybrid consisted of single-domain PbTiO3 coated by CdS particles was selected as a model material to prove that the alternating piezoelectric field induced by periodic stress can destroy shielding effect.
Abstract: The polarization field with the function in carrier separation has aroused substantial interest. For heterojunction complexes, however, the static polarization field will be inevitably shielded by a large number of carriers. Herein, a novel hybrid consisted of single-domain PbTiO3 coated by CdS particles was selected as a model material to prove that the alternating piezoelectric field induced by periodic stress can destroy shielding effect. After the introduction of alternating piezoelectric potential by using ultrasonication, PbTiO3/CdS-10 % exhibited a much higher H2 production rate by piezo-photocatalysis (849.0 μmol h−1 g−1) than by individual piezocatalysis (400.6 μmol h−1 g−1) or photocatalysis (98.9 μmol h−1 g−1). Furthermore, the finite element simulation shows that PbTiO3/CdS heterostructure has a superior piezoelectric potential difference compare to pure PbTiO3 or pure CdS. Based on data analysis, the mechanism about the piezo-photo coupling effect was proposed, which will provide a reference for the design and development of high-efficiency piezo-photocatalyst.