Showing papers on "Platinum published in 2017"
TL;DR: H2-air performance gains are demonstrated with an iron-nitrogen-carbon catalyst synthesized with two nitrogen precursors that developed hierarchical porosity, and the proposed catalytically active site is FeN4.
Abstract: Platinum group metal–free (PGM-free) metal-nitrogen-carbon catalysts have emerged as a promising alternative to their costly platinum (Pt)–based counterparts in polymer electrolyte fuel cells (PEFCs) but still face some major challenges, including (i) the identification of the most relevant catalytic site for the oxygen reduction reaction (ORR) and (ii) demonstration of competitive PEFC performance under automotive-application conditions in the hydrogen (H 2 )–air fuel cell. Herein, we demonstrate H 2 -air performance gains achieved with an iron-nitrogen-carbon catalyst synthesized with two nitrogen precursors that developed hierarchical porosity. Current densities recorded in the kinetic region of cathode operation, at fuel cell voltages greater than ~0.75 V, were the same as those obtained with a Pt cathode at a loading of 0.1 milligram of Pt per centimeter squared. The proposed catalytic active site, carbon-embedded nitrogen-coordinated iron (FeN 4 ), was directly visualized with aberration-corrected scanning transmission electron microscopy, and the contributions of these active sites associated with specific lattice-level carbon structures were explored computationally.
1,159 citations
TL;DR: The Ru@C2N electrocatalyst, made of Ru nanoparticles dispersed within a nitrogenated holey two-dimensional carbon structure, exhibits high turnover frequencies and superior stability in both acidic and alkaline media, comparable to, or even better than, the Pt/C catalyst for the HER.
Abstract: Ruthenium nanoparticles homogeneously dispersed in a nitrogenated, two-dimensional carbon matrix show high turnover frequency and small overpotential for hydrogen evolution reaction both in acidic and alkaline media. The hydrogen evolution reaction (HER) is a crucial step in electrochemical water splitting and demands an efficient, durable and cheap catalyst if it is to succeed in real applications1,2,3. For an energy-efficient HER, a catalyst must be able to trigger proton reduction with minimal overpotential4 and have fast kinetics5,6,7,8,9. The most efficient catalysts in acidic media are platinum-based, as the strength of the Pt–H bond10 is associated with the fastest reaction rate for the HER11,12. The use of platinum, however, raises issues linked to cost and stability in non-acidic media. Recently, non-precious-metal-based catalysts have been reported, but these are susceptible to acid corrosion and are typically much inferior to Pt-based catalysts, exhibiting higher overpotentials and lower stability13,14,15. As a cheaper alternative to platinum, ruthenium possesses a similar bond strength with hydrogen (∼65 kcal mol–1)16, but has never been studied as a viable alternative for a HER catalyst. Here, we report a Ru-based catalyst for the HER that can operate both in acidic and alkaline media. Our catalyst is made of Ru nanoparticles dispersed within a nitrogenated holey two-dimensional carbon structure (Ru@C2N). The Ru@C2N electrocatalyst exhibits high turnover frequencies at 25 mV (0.67 H2 s−1 in 0.5 M H2SO4 solution; 0.75 H2 s−1 in 1.0 M KOH solution) and small overpotentials at 10 mA cm–2 (13.5 mV in 0.5 M H2SO4 solution; 17.0 mV in 1.0 M KOH solution) as well as superior stability in both acidic and alkaline media. These performances are comparable to, or even better than, the Pt/C catalyst for the HER.
1,105 citations
TL;DR: It is reported that platinum atomically dispersed on α-molybdenum carbide (α-MoC) enables low-temperature (150–190 degrees Celsius), base-free hydrogen production through APRM, with an average turnover frequency reaching 18,046 moles of hydrogen per mole of platinum per hour.
Abstract: Polymer electrolyte membrane fuel cells (PEMFCs) running on hydrogen are attractive alternative power supplies for a range of applications, with in situ release of the required hydrogen from a stable liquid offering one way of ensuring its safe storage and transportation before use. The use of methanol is particularly interesting in this regard, because it is inexpensive and can reform itself with water to release hydrogen with a high gravimetric density of 18.8 per cent by weight. But traditional reforming of methanol steam operates at relatively high temperatures (200-350 degrees Celsius), so the focus for vehicle and portable PEMFC applications has been on aqueous-phase reforming of methanol (APRM). This method requires less energy, and the simpler and more compact device design allows direct integration into PEMFC stacks. There remains, however, the need for an efficient APRM catalyst. Here we report that platinum (Pt) atomically dispersed on α-molybdenum carbide (α-MoC) enables low-temperature (150-190 degrees Celsius), base-free hydrogen production through APRM, with an average turnover frequency reaching 18,046 moles of hydrogen per mole of platinum per hour. We attribute this exceptional hydrogen production-which far exceeds that of previously reported low-temperature APRM catalysts-to the outstanding ability of α-MoC to induce water dissociation, and to the fact that platinum and α-MoC act in synergy to activate methanol and then to reform it.
944 citations
TL;DR: In this paper, a detailed kinetic study of hydrogen adsorption and evolution on Pt(111) in a wide pH range is presented, highlighting the role of reorganization of interfacial water to accommodate charge transfer through the electric double layer, the energetics of which are controlled by how strongly water interacts with the interfacial field.
Abstract: Hydrogen evolution on platinum is a key reaction for electrocatalysis and sustainable energy storage, yet its pH-dependent kinetics are not fully understood. Here we present a detailed kinetic study of hydrogen adsorption and evolution on Pt(111) in a wide pH range. Electrochemical measurements show that hydrogen adsorption and hydrogen evolution are both slow in alkaline media, consistent with the observation of a shift in the rate-determining step for hydrogen evolution. Adding nickel to the Pt(111) surface lowers the barrier for hydrogen adsorption in alkaline solutions and thereby enhances the hydrogen evolution rate. We explain these observations with a model that highlights the role of the reorganization of interfacial water to accommodate charge transfer through the electric double layer, the energetics of which are controlled by how strongly water interacts with the interfacial field. The model is supported by laser-induced temperature-jump measurements. Our model sheds light on the origin of the slow kinetics for the hydrogen evolution reaction in alkaline media. Despite its role in electrocatalysis and hydrogen generation, a complete understanding of the hydrogen evolution reaction on platinum remains elusive. Here, a detailed kinetic study of hydrogen adsorption and evolution on Pt(111) highlights the role of interfacial water reorganization in the hydrogen adsorption step.
685 citations
TL;DR: Pt2 dimers can be fabricated with a bottom–up approach on graphene using atomic layer deposition, through proper nucleation sites creation, Pt1 single-atom deposition and attaching a secondary Pt atom selectively on the preliminary one.
Abstract: Supported metal clusters containing only a few atoms are of great interest. Progress has been made in synthesis of metal single-atom catalysts. However, precise synthesis of metal dimers on high-surface area support remains a grand challenge. Here, we show that Pt2 dimers can be fabricated with a bottom–up approach on graphene using atomic layer deposition, through proper nucleation sites creation, Pt1 single-atom deposition and attaching a secondary Pt atom selectively on the preliminary one. Scanning transmission electron microscopy, x-ray absorption spectroscopy, and theoretical calculations suggest that the Pt2 dimers are likely in the oxidized form of Pt2Ox. In hydrolytic dehydrogenation of ammonia borane, Pt2 dimers exhibit a high specific rate of 2800 molH2 molPt
−1 min−1 at room temperature, ~17- and 45-fold higher than graphene supported Pt single atoms and nanoparticles, respectively. These findings open an avenue to bottom–up fabrication of supported atomically precise ultrafine metal clusters for practical applications. Controlled fabrication of few-atoms supported catalysts is a major challenge in the synthesis of nanomaterials. Here, the authors show a bottom-up approach to precisely synthesize platinum dimers supported on graphene, which display higher catalytic activity and stability than single atoms and nanoparticles.
645 citations
TL;DR: An efficient approach to construct one-dimensional metal/sulfide heterostructures by directly sulfuring highly composition-segregated platinum-nickel nanowires is reported, highlighting a potentially powerful interface-engineering strategy for designing multicomponent heterostructure with advanced performance in hydrogen evolution reaction and beyond.
Abstract: Comprising abundant interfaces, multicomponent heterostructures can integrate distinct building blocks into single entities and yield exceptional functionalities enabled by the synergistic components. Here we report an efficient approach to construct one-dimensional metal/sulfide heterostructures by directly sulfuring highly composition-segregated platinum-nickel nanowires. The heterostructures possess a high density of interfaces between platinum-nickel and nickel sulfide components, which cooperate synergistically towards alkaline hydrogen evolution reaction. The platinum-nickel/nickel sulfide heterostructures can deliver a current density of 37.2 mA cm−2 at an overpotential of 70 mV, which is 9.7 times higher than that of commercial Pt/C. The heterostructures also offer enhanced stability revealed by long-term chronopotentiometry measurements. The present work highlights a potentially powerful interface-engineering strategy for designing multicomponent heterostructures with advanced performance in hydrogen evolution reaction and beyond. Multicomponent, nanoscale heterostructures may exhibit notable catalytic properties imparted by the various building blocks. Here, the authors fabricate metal/sulfide heterostructures via direct sulfurization of segregated platinum-nickel nanowires, and assess their hydrogen evolution performance.
621 citations
TL;DR: A carbon black-supported cost-effective, efficient and durable platinum single-atom electrocatalyst with carbon monoxide/methanol tolerance for the cathodic oxygen reduction reaction in fuel cells is reported.
Abstract: For the large-scale sustainable implementation of polymer electrolyte membrane fuel cells in vehicles, high-performance electrocatalysts with low platinum consumption are desirable for use as cathode material during the oxygen reduction reaction in fuel cells. Here we report a carbon black-supported cost-effective, efficient and durable platinum single-atom electrocatalyst with carbon monoxide/methanol tolerance for the cathodic oxygen reduction reaction. The acidic single-cell with such a catalyst as cathode delivers high performance, with power density up to 680 mW cm-2 at 80 °C with a low platinum loading of 0.09 mgPt cm-2, corresponding to a platinum utilization of 0.13 gPt kW-1 in the fuel cell. Good fuel cell durability is also observed. Theoretical calculations reveal that the main effective sites on such platinum single-atom electrocatalysts are single-pyridinic-nitrogen-atom-anchored single-platinum-atom centres, which are tolerant to carbon monoxide/methanol, but highly active for the oxygen reduction reaction.
547 citations
TL;DR: A potential‐cycling method is demonstrated to synthesize a catalyst comprising single Pt atoms on CoP‐based nanotube arrays supported by a Ni foam, termed PtSA‐NT‐NF, which is directly used as HER cathodes and its electrocatalytic stability is better than that of Pt/C.
Abstract: Single-atom catalysts (SACs) have exhibited high activities for the hydrogen evolution reaction (HER) electrocatalysis in acidic or alkaline media, when they are used with binders on cathodes. However, to date, no SACs have been reported for the HER electrocatalysis in neutral media. We demonstrate a potential-cycling method to synthesize a catalyst comprising single Pt atoms on CoP-based nanotube arrays supported by a Ni foam, termed PtSA-NT-NF. This binder-free catalyst is centimeter-scale and scalable. It is directly used as HER cathodes, whose performances at low and high current densities in phosphate buffer solutions (pH 7.2) are comparable to and better than, respectively, those of commercial Pt/C. The Pt mass activity of PtSA-NT-NF is 4 times of that of Pt/C, and its electrocatalytic stability is also better than that of Pt/C. This work provides a large-scale production strategy for binder-free Pt SAC electrodes for efficient HER in neutral media.
411 citations
327 citations
TL;DR: In this article, the role of the support may have a significant effect on the catalytic properties, similar to that of the ligand molecules in homogeneous catalysts, and the support effect was demonstrated by preparing a single-atom platinum catalyst on two different supports.
Abstract: Single-atom catalysts (SACs) provide an ideal platform for reducing noble-metal usage. SACs also exhibit unusual catalytic properties due to the absence of a metal surface. The role of the support may have a significant effect on the catalytic properties, similar to that of the ligand molecules in homogeneous catalysts. Here, the support effect was demonstrated by preparing a single-atom platinum catalyst on two different supports: titanium carbide (Pt1/TiC) and titanium nitride (Pt1/TiN). The formation of single-atom Pt was confirmed by STEM, EXAFS, and in situ IR spectroscopy. Pt1/TiC showed higher activity, selectivity, and stability for electrochemical H2O2 production than Pt1/TiN. Density functional theory calculations presented that oxygen species have strong affinity into Pt1/TiN, possibly acting as surface poisoning species, and Pt1/TiC preserves oxygen–oxygen bonds more with higher selectivity toward H2O2 production. This work clearly shows that the support in SACs actively participates in the su...
320 citations
TL;DR: A facile approach is demonstrated to generate atomically dispersed platinum via photochemical reduction of frozen chloroplatinic acid solution using ultraviolet light to obtain atomically-dispersed platinum catalysts with high electrocatalytic performance.
Abstract: Photochemical solution-phase reactions have been widely applied for the syntheses of nanocrystals. In particular, tuning of the nucleation and growth of solids has been a major area of focus. Here we demonstrate a facile approach to generate atomically dispersed platinum via photochemical reduction of frozen chloroplatinic acid solution using ultraviolet light. Using this iced-photochemical reduction, the aggregation of atoms is prevented, and single atoms are successfully stabilized. The platinum atoms are deposited on various substrates, including mesoporous carbon, graphene, carbon nanotubes, titanium dioxide nanoparticles, and zinc oxide nanowires. The atomically dispersed platinum on mesoporous carbon exhibits efficient catalytic activity for the electrochemical hydrogen evolution reaction, with an overpotential of only 65 mV at a current density of 100 mA cm−2 and long-time durability (>10 h), superior to state-of-the-art platinum/carbon. This iced-photochemical reduction may be extended to other single atoms, for example gold and silver, as demonstrated in this study. Photochemical synthesis is a popular approach to fabricate metallic nanoparticles, however stabilizing individually-dispersed atoms by this method remains challenging. Here, the authors freeze their precursor solution prior to UV irradiation to obtain atomically-dispersed platinum catalysts with high electrocatalytic performance.
TL;DR: In this paper, the authors achieved pseudo-atomic-scale dispersion of Pt, i.e. individual atoms or subnanometer clusters, on the sidewalls of single-walled carbon nanotubes (SWNTs) with a simple and readily upscalable electroplating deposition method.
Abstract: The development of effective and inexpensive hydrogen evolution reaction (HER) electrocatalysts for future renewable energy systems is highly desired. Platinum-based materials are the most active electrocatalysts for catalyzing HER, but reducing the use of Pt is required because of the high price and scarcity of Pt. Here, we achieve pseudo-atomic-scale dispersion of Pt, i.e. individual atoms or subnanometer clusters, on the sidewalls of single-walled carbon nanotubes (SWNTs) with a simple and readily upscalable electroplating deposition method. These SWNTs activated with an ultralow amount of Pt exhibit activity similar to that of commercial Pt/C with a notably higher (∼66–333-fold) Pt loading for catalyzing the HER under the acidic conditions required in proton exchange membrane technology. These catalysts resemble pseudo-atomic-scale Pt systems which are mainly composed of a few to tens of Pt atoms dispersed on the sidewalls of the SWNTs. The Pt loading is only 0.19–0.75 atom % at the electrode surface,...
TL;DR: Ceria (CeO2) supports are unique in their ability to trap ionic platinum (Pt), providing exceptional stability for isolated single atoms of Pt, and upon oxidation the Pt–Sn clusters readily revert to the atomically dispersed species on CeO2, making Pt– Sn/Ce O2 a fully regenerable catalyst.
Abstract: Ceria (CeO2) supports are unique in their ability to trap ionic platinum (Pt), providing exceptional stability for isolated single atoms of Pt. The reactivity and stability of single-atom Pt species was explored for the industrially important light alkane dehydrogenation reaction. The single-atom Pt/CeO2 catalysts are stable during propane dehydrogenation, but are not selective for propylene. DFT calculations show strong adsorption of the olefin produced, leading to further unwanted reactions. In contrast, when tin (Sn) is added to CeO2, the single-atom Pt catalyst undergoes an activation phase where it transforms into Pt–Sn clusters under reaction conditions. Formation of small Pt–Sn clusters allows the catalyst to achieve high selectivity towards propylene because of facile desorption of the product. The CeO2-supported Pt–Sn clusters are very stable, even during extended reaction at 680 °C. Coke formation is almost completely suppressed by adding water vapor to the feed. Furthermore, upon oxidation the Pt–Sn clusters readily revert to the atomically dispersed species on CeO2, making Pt–Sn/CeO2 a fully regenerable catalyst.
TL;DR: Three of these phases were studied for their HER activity and by X-ray photoelectron spectroscopy for the first time and show excellent activity in the same range as the recently reported α-MoB and β-Mo2 C phases, indicating a strong boron-dependency of these borides for the HER.
Abstract: Molybdenum-based materials have been considered as alternative catalysts to noble metals, such as platinum, for the hydrogen evolution reaction (HER). We have synthesized four binary bulk molybdenum borides Mo2 B, α-MoB, β-MoB, and MoB2 by arc-melting. All four phases were tested for their electrocatalytic activity (linear sweep voltammetry) and stability (cyclic voltammetry) with respect to the HER in acidic conditions. Three of these phases were studied for their HER activity and by X-ray photoelectron spectroscopy (XPS) for the first time; MoB2 and β-MoB show excellent activity in the same range as the recently reported α-MoB and β-Mo2 C phases, while the molybdenum richest phase Mo2 B show significantly lower HER activity, indicating a strong boron-dependency of these borides for the HER. In addition, MoB2 and β-MoB show long-term cycle stability in acidic solution.
TL;DR: It is reported that the thermoneutral catalyst can be prepared by simple doping of a platinum atom into a molecule-like gold nanocluster, which represents a class of catalysts that bridge homogeneous and heterogeneous catalysis and may provide a platform for the discovery of finely optimized catalysts.
Abstract: The theoretically predicted volcano plot for hydrogen production shows the best catalyst as the one that ensures that the hydrogen binding step is thermodynamically neutral. However, the experimental realization of this concept has suffered from the inherent surface heterogeneity of solid catalysts. It is even more challenging for molecular catalysts because of their complex chemical environment. Here, we report that the thermoneutral catalyst can be prepared by simple doping of a platinum atom into a molecule-like gold nanocluster. The catalytic activity of the resulting bimetallic nanocluster, PtAu24(SC6H13)18, for the hydrogen production is found to be significantly higher than reported catalysts. It is even better than the benchmarking platinum catalyst. The molecule-like bimetallic nanocluster represents a class of catalysts that bridge homogeneous and heterogeneous catalysis and may provide a platform for the discovery of finely optimized catalysts. Volcano plots for electrocatalytic hydrogen production show the best catalysts as those ensuring the hydrogen binding step is thermodynamically neutral. Here, the authors report fabrication of a highly active thermoneutral electrocatalyst via doping of a single platinum atom into a gold nanocluster.
TL;DR: It is demonstrated that the Au@Pt NPs could enhance detection sensitivity by 2 orders of magnitude, more than double that of conventional AuNPs.
Abstract: Au nanoparticles (AuNPs) as signal reporters have been utilized in colorimetric in vitro diagnostics (IVDs) for decades. Nevertheless, it remains a grand challenge to substantially enhance the detection sensitivity of AuNP-based IVDs as confined by the inherent plasmonics of AuNPs. In this work, we circumvent this confinement by developing unique dual-functional AuNPs that were engineered by coating conventional AuNPs with ultrathin Pt skins of sub-10 atomic layers (i.e., Au@Pt NPs). The Au@Pt NPs retain the plasmonic activity of initial AuNPs while possessing ultrahigh catalytic activity enabled by Pt skins. Such dual functionalities, plasmonics and catalysis, offer two different detection alternatives: one produced just by the color from plasmonics (low-sensitivity mode) and the second more sensitive color catalyzed from chromogenic substrates (high-sensitivity mode), achieving an “on-demand” tuning of the detection performance. Using lateral flow assay as a model IVD platform and conventional AuNPs as ...
TL;DR: The ultrafine structure of atomically dispersed Cu-Pt dual sites was confirmed with X-ray absorption fine structure (XAFS) measurements and exhibit excellent HER properties in acidic solution with an overpotential of only 22.8 mV.
Abstract: Designing highly active catalysts at an atomic scale is required to drive the hydrogen evolution reaction (HER). Copper–platinum (Cu-Pt) dual sites were alloyed with palladium nanorings (Pd NRs) containing 1.5 atom % Pt, using atomically dispersed Cu on ultrathin Pd NRs as seeds. The ultrafine structure of atomically dispersed Cu-Pt dual sites was confirmed with X-ray absorption fine structure (XAFS) measurements. The Pd/Cu-Pt NRs exhibit excellent HER properties in acidic solution with an overpotential of only 22.8 mV at a current density of 10 mA cm−2 and a high mass current density of 3002 A g−1(Pd+Pt) at a −0.05 V potential.
TL;DR: Density functional calculations explain the observations on the identity and concentration of alkali cations on the non-Nernstian pH shift, and demonstrate that cation-hydroxyl co-adsorption causes the apparent pH dependence of "hydrogen" adsorption in the step sites of platinum electrodes.
Abstract: The successful deployment of advanced energy-conversion systems depends critically on our understanding of the fundamental interactions of the key adsorbed intermediates (hydrogen *H and hydroxyl *OH) at electrified metal-aqueous electrolyte interfaces. The effect of alkali metal cations (Li+ , Na+ , K+ , Cs+ ) on the non-Nernstian pH shift of the step-related voltammetric peak of the Pt(553) electrode is investigated over a wide pH window (1 to 13) by means of experimental and computational methods. The co-adsorbed alkali cations along the step weaken the OH adsorption at the step sites, causing a positive shift of the potential of the step-related peak on Pt(553). Density functional calculations explain the observations on the identity and concentration of alkali cations on the non-Nernstian pH shift, and demonstrate that cation-hydroxyl co-adsorption causes the apparent pH dependence of "hydrogen" adsorption in the step sites of platinum electrodes.
TL;DR: Fluorescence quenching was observed upon the interaction of GQDs with the target endotoxin (LPS), whereby the PABA tags acted as highly specific recognition receptors of the LPS core polysaccharide region.
Abstract: Magnetocatalytic hybrid Janus micromotors encapsulating phenylboronic acid (PABA) modified graphene quantum dots (GQDs) are described herein as ultrafast sensors for the detection of deadly bacteria endotoxins. A bottom-up approach was adopted to synthesize an oil-in-water emulsion containing the GQDs along with a high loading of platinum and iron oxide nanoparticles on one side of the Janus micromotor body. The two different "active regions" enable highly efficient propulsion in the presence of hydrogen peroxide or magnetic actuation without the addition of a chemical fuel. Fluorescence quenching was observed upon the interaction of GQDs with the target endotoxin (LPS), whereby the PABA tags acted as highly specific recognition receptors of the LPS core polysaccharide region. Such adaptive hybrid operation and highly specific detection hold considerable promise for diverse clinical, agrofood, and biological applications and integration in future lab-on-chip technology.
TL;DR: In this paper, a 3D ordered mesoporous Fe-N/C with open porous structure is successfully synthesized and the obtained shape is a rhombic dodecahedron which corresponds to a single mesoporus crystal with body-centered cubic structure (Im-3m).
TL;DR: A dynamic structural behavior of Pt nanoparticles on the ceria surface under reducing/oxidizing conditions was found at moderate temperatures and exploited to enhance the catalytic activity of Pt/CeO2 -based exhaust gas catalysts.
Abstract: A dynamic structural behavior of Pt nanoparticles on the ceria surface under reducing/oxidizing conditions was found at moderate temperatures ( H2>C3H6). This dynamic nature of Pt on ceria at such low temperatures (250–500 °C) was additionally confirmed by in situ environmental transmission electron microscopy. A general concept is proposed to adjust the noble metal dispersion (size, structure), for example, during operation of an exhaust gas catalyst.
TL;DR: The confinement of platinum nanoparticles within the molybdenum disulfide layered structure leads to enhanced hydrogen evolution reaction activity and stability compared to catalysts dispersed on carbon support, which points a way forward for using bulk intercalated compounds for energy related applications.
Abstract: Interface confined reactions, which can modulate the bonding of reactants with catalytic centres and influence the rate of the mass transport from bulk solution, have emerged as a viable strategy for achieving highly stable and selective catalysis. Here we demonstrate that 1T′-enriched lithiated molybdenum disulfide is a highly powerful reducing agent, which can be exploited for the in-situ reduction of metal ions within the inner planes of lithiated molybdenum disulfide to form a zero valent metal-intercalated molybdenum disulfide. The confinement of platinum nanoparticles within the molybdenum disulfide layered structure leads to enhanced hydrogen evolution reaction activity and stability compared to catalysts dispersed on carbon support. In particular, the inner platinum surface is accessible to charged species like proton and metal ions, while blocking poisoning by larger sized pollutants or neutral molecules. This points a way forward for using bulk intercalated compounds for energy related applications. Interface confined reactions are a viable strategy for achieving stable and selective catalysts. Here, the authors demonstrate that 1T'-enriched lithiated MoS2 can reduce metal ions in situ, forming zero valent platinum nanoparticle-intercalated MoS2, with enhanced hydrogen evolution activity.
TL;DR: In this article, an efficient nickel hydroxide-promoted PtNi(OH)x/γ-Al 2 O 3 catalysts for room temperature HCHO oxidation was developed.
Abstract: Rational design of efficient noble metal catalysts and its application process by the interface promoted strategy is an emerging research field. Herein, highly efficient nickel hydroxide promoted PtNi(OH)x/γ-Al 2 O 3 catalysts for room temperature HCHO oxidation was developed. PtNi(OH)x/γ-Al 2 O 3 demonstrates remarkably better performance than the state of the art non-reductive oxide supported Pt catalysts, and ranges among the best performance of the reductive metal oxide supported Pt catalysts. A (>)99% HCHO conversion and a (>)100 h stable performance at 30 °C were obtained over PtNi(OH)x/γ-Al 2 O 3 with a 0.3 wt% Pt loading amount. Various characterizations, including in situ DRIFTS study, were performed to understand the reason for the enhanced performance of PtNi(OH)x/γ-Al 2 O 3 . The superior performance is attributed to the formation of enormous Pt/Ni(OH)x interface, and the preferred hydroxyl facilitated HCHO oxidation pathway through formate oxidation by the abundant associated hydroxyl groups nearby the Pt active sites. Such hydroxyl groups confined interface promotion strategy may bring new insight into the designing of highly efficient bimetallic catalysts and its potential technological applications for HCHO removal.
TL;DR: In this article, a model to design ORR active sites on extended surfaces can also be used to solve this apparent contradiction and provide accurate design rules for nanoparticles, since only surfaces and nanostructures with concave defects can surpass the activity of Pt(111), whereas convex defects are inactive.
Abstract: Experiments on model surfaces commonly help in identifying the structural sensitivity of catalytic reactions. Nevertheless, their conclusions do not frequently lead to devising superior "real-world" catalysts. For instance, this is true for single-crystal platinum electrodes and the oxygen reduction reaction (ORR), an important reaction for sustainable energy conversion. Pt(111) is substantially enhanced by steps, reaching a maximum at short terrace lengths of 3-4 atoms. Conversely, regular platinum nanoparticles with similar undercoordinated defects are less active than Pt(111) and their activity increases alongside the terrace-to-defect ratio. We show here that a model to design ORR active sites on extended surfaces can also be used to solve this apparent contradiction and provide accurate design rules for nanoparticles. Essentially, only surfaces and nanostructures with concave defects can surpass the activity of Pt(111), whereas convex defects are inactive. Importantly, only the latter are present in regular nanoparticles, which is why we design various concave nanoparticles with high activities.
TL;DR: In this article, a facile method for synthesizing two-dimensional nickel disulfide (NiS 2 ) by using Ni(OH) 2 on nickel foam as substrate was reported.
TL;DR: Platinum nanoparticles supported on graphite-rich boron carbide show a 50–100% increase in activity in acidic media and improved cycle stability compared to commercial carbon supported platinum nanoparticles, showing that purely electronic metal-support interactions can significantly improve oxygen reduction activity.
Abstract: D-band engineering via alloying platinum is a leading design principle for advanced oxygen reduction electrocatalysts, but stability remains a concern. Here the authors make Pt nanoparticles supported on graphite-rich boron carbide for enhanced activity and stability, iso…
TL;DR: The DMF-solvothermally synthesized nanocrystalline NiSe2 (DNC-NiSe2) exhibits superior performance of hydrogen evolution reaction (HER); it has a very low onset overpotential, a very high cathode current density, and an excellent long-term stability.
Abstract: For the first time, self-assembled coral-like hierarchical architecture constructed by NiSe2 nanocrystals has been synthesized via a facile one-pot DMF-solvothermal method. Compared with hydrothermally synthesized NiSe2 (H-NiSe2), the DMF-solvothermally synthesized nanocrystalline NiSe2 (DNC-NiSe2) exhibits superior performance of hydrogen evolution reaction (HER): it has a very low onset overpotential of ∼136 mV (vs RHE), a very high cathode current density of 40 mA/cm2 at ∼200 mV (vs RHE), and an excellent long-term stability; most importantly, it delivers an ultrasmall Tafel slope of 29.4 mV dec–1, which is the lowest ever reported for NiSe2-based catalysts, and even lower than that of precious platinum (Pt) catalyst (30.8 mV dec–1). The superior HER performance of DNC-NiSe2 is attributed to the unique self-assembled coral-like network, which is a benefit to form abundant active sites and facilitates the charge transportation due to the inherent high conductivity of NiSe2 nanocrystals. The DNC-NiSe2 is...
TL;DR: In this article, a facile strategy was developed to prepare P-doped 2H-MoS2 film on conductive substrate via low-temperature heat treatment, which showed improved catalytic performance in H2 generation.
Abstract: Molybdenum disulfide (MoS2) has been considered as a promising alternative to platinum (Pt)-based catalyst for hydrogen evolution reaction (HER) due to its low cost and high catalytic activity. However, stable 2H phase of MoS2 (2H-MoS2) exhibits low catalytic activity in HER due to the inert basal plane and S-edge. Thus, to exploit the basal plane and S-edge for additional electrocatalytic activity, a facile strategy is developed to prepare P-doped 2H-MoS2 film on conductive substrate via low-temperature heat treatment. Due to the inherent difficulty of P-doping into MoS2 crystal structure, oxygen (O)-doping is utilized to aid the P-doping process, as supported by the first-principles calculations. Interestingly, P-doping could dramatically reduce Mo valence charge, which results in the functionalization of the inert MoS2 basal plane and S-edge. In agreement with simulation results, P-doped 2H-MoS2 electrode exhibits enhanced catalytic performance in H2 generation with low onset potential (130 mV) and small Tafel slope of 49 mV dec−1. The enhanced catalytic performance arises from the synergistic effect of the activated basal plane, S-edge, and Mo-edge sites, leading to favorable hydrogen adsorption energies. Most importantly, improved cyclic stability is achieved, which reveals chemically inert properties of P-doped 2H-MoS2 in acidic electrolyte.
TL;DR: In this paper, Wool-like metal electrodes used to produce nonthermal plasma were determined to serve as efficient catalysts for ammonia synthesis under atmospheric pressure without heating, and the catalytic activity of Pt, Pd, Ag, Cu, and Ni wools increased as the experiment was repeated, while that of Au, Fe, Mo, Ti, W, and Al was almost constant.
Abstract: Developing an ammonia synthesis process from N2 and H2 is of interest in the catalysis and hydrogen research community. Wool-like metal electrodes used to produce nonthermal plasma were determined to serve as efficient catalysts for ammonia synthesis under atmospheric pressure without heating. The catalytic activity of Pt, Pd, Ag, Cu, and Ni wools increased as the experiment was repeated, while that of Au, Fe, Mo, Ti, W, and Al was almost constant. The activity change was mainly due to migration of metals from the electrode to the inner wall of a silica reactor or increases in surface areas of metal catalysts. The order of the activity at each initial experiment was Au > Pt > Pd > Ag > Cu > Fe > Mo > Ni > W > Ti > Al. DFT calculations using Gaussian 09 and CASTEP were applied for energy changes in a reaction M3 + 1/2 N2 → M3N and in adsorption of a nitrogen atom on metal surface, in which M3 was a virtual minimum unit of the metal surface. The reactions were assumed to be an essential step in the ammonia ...
TL;DR: In this paper, an integrated approach using density functional theory (DFT), kinetics, and in situ X-ray spectroscopies was used to demonstrate how Zn addition to Pt/SiO2 formed high symmetry Pt1Zn1 nanoparticle alloys with isolated Pt surface sites that enable near 100% C2H4 selectivity during ethane dehydrogenation (EDH) with a 6-fold higher turnover rate (TOR) per mole of surface Pt at 600 °C compared to monometallic Pt/ SiO2.
Abstract: Supported metal nanoparticles are vital as heterogeneous catalysts in the chemical transformation of hydrocarbon resources. The catalytic properties of these materials are governed by the surface electronic structure and valence orbitals at the active metal site and can be selectively tuned with promoters or by alloying. Through an integrated approach using density functional theory (DFT), kinetics, and in situ X-ray spectroscopies, we demonstrate how Zn addition to Pt/SiO2 forms high symmetry Pt1Zn1 nanoparticle alloys with isolated Pt surface sites that enable near 100% C2H4 selectivity during ethane dehydrogenation (EDH) with a 6-fold higher turnover rate (TOR) per mole of surface Pt at 600 °C compared to monometallic Pt/SiO2. Furthermore, we show how DFT calculations accurately reproduce the resonant inelastic X-ray spectroscopic (RIXS) signatures of Pt 5d valence orbitals in the Pt/SiO2 and PtZn/SiO2 catalysts that correlate with their kinetic performance during EDH. This technique reveals that Zn mo...