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Bulk properties of transition metal nitrides, an emerging class of materials studied using various DFT exchange and correlation functionals.

Electrochemical nitrogen reduction reaction (ENRR) under ambient conditions is beneficial compared to the energy intensive thermochemical Haber–Bosch process for NH3 production. Here, periodic density functional theory (DFT) calculations are carried out to study the ENRR on transition metal oxynitride (TMNO) catalysts. Our calculations show that the ENRR occurs at thermodynamically more favorable surface nitrogen vacancy (N-vac) sites compared to surface oxygen vacancy (O-vac) sites. The DFT results show that TiNO efficiently catalyzes the ENRR at a low applied potential (U) and its ENRR activity is predicted to be similar to that of VNO, a previously identified excellent ENRR catalyst. We observed a volcano like relationship between the DFT calculated nitrogen binding energy (NBE) and the limiting potential (UL), which suggests that the NBE can be used as a descriptor of the ENRR activity on TMNO based catalysts.

Transition metal based materials containing Fe have drawn great attention as oxygen evolution reaction (OER) catalysts. The nature of the electrocatalytic active species remains under debate due to the ambiguous physicochemical properties of the catalyst materials, such as the oxidation states and crystal structures. Here, in order to address this issue, transition metal Prussian blue analogues (TM-PBA, Na(TM)(Fe)(CN)6, TM = V, Fe, Co, and Ni) with an isomorphous structure are investigated for OER catalysis. Our combined experimental measurements and density functional theory (DFT) calculations reveal that TM-PBAs exhibit volcano-like OER activity with Ni-PBA located near the top of the volcano. Such a volcano-like activity profile can be attributed to the distinctive binding energy difference between *O and *OH on different TM-PBAs surfaces. This work demonstrates that TM-PBAs can be used as platform materials for understanding structure-property-activity relationships in OER catalysts.

Pt and Pd monolayer on transition metal nitrides as efficient and low-cost catalysts for hydrogen evolution reaction.

Significance Direct ethanol fuel cells are attracting growing attention as portable power sources due to their advantages such as higher mass-energy density than hydrogen and less toxicity than methanol. However, it is challenging to achieve the complete electrooxidation to generate 12 electrons per ethanol, resulting in a low fuel utilization efficiency. This manuscript reports the complete ethanol electrooxidation by engineering efficient catalysts via single-atom modification. The combined electrochemical measurements, in situ characterization, and density functional theory calculations unravel synergistic effects of single Rh atoms and Pt nanocubes and identify reaction pathways leading to the selective C–C bond cleavage to oxidize ethanol to CO 2 . This study provides a unique single-atom approach to tune the activity and selectivity toward complicated electrocatalytic reactions.

Summary Selective upgrading of underutilized ethane in shale gas with greenhouse gas CO2 can produce syngas via dry reforming (C–C bond scission) or ethylene via oxidative dehydrogenation (C–H bond scission). However, it remains challenging to identify active sites responsible for the selective bond cleavage in ethane due to the complexity of supported catalysts. Herein, the ethane-CO2 reaction over CeO2-supported catalysts was investigated to unravel the functions of distinct interfacial sites by combining kinetic measurements with in situ characterizations and calculations: the Pd/CeOx interface is responsible for supplying reactive oxygen species, electron-deficient oxygen species on Pd surface boosts the non-selective bond scission to produce syngas, electron-enriched oxygen in the FeOx/Pd interface enhances the selective scission of C–H bond to yield ethylene, and the FeOx/CeO2 interaction mediates oxygen supply and confines metal ensembles. The current work identifies opportunities for using different interfacial structures in upgrading abundant shale gas and CO2.

The electrochemical CO2 reduction reaction (CO2 RR) to yield synthesis gas (syngas, CO and H2 ) has been considered as a promising method to realize the net reduction in CO2 emission. However, it is challenging to balance the CO2 RR activity and the CO/H2 ratio. To address this issue, nitrogen-doped carbon supported single-atom catalysts are designed as electrocatalysts to produce syngas from CO2 RR. While Co and Ni single-atom catalysts are selective in producing H2 and CO, respectively, electrocatalysts containing both Co and Ni show a high syngas evolution (total current >74 mA cm-2 ) with CO/H2 ratios (0.23-2.26) that are suitable for typical downstream thermochemical reactions. Density functional theory calculations provide insights into the key intermediates on Co and Ni single-atom configurations for the H2 and CO evolution. The results present a useful case on how non-precious transition metal species can maintain high CO2 RR activity with tunable CO/H2 ratios.

The electrochemical carbon dioxide reduction reaction (CO2RR) using copper (Cu)-based catalysts has received significant attention mainly because Cu is an element capable of producing hydrocarbons and oxygenates. One possible way to control the CO2RR performance at the electrode interface is by modifying catalysts with specific functional groups of different polymeric binders, which are necessary components in the process of electrode fabrication. However, the modification effect of the key functional groups on the CO2RR activity and selectivity is poorly understood over Cu-based catalysts. In this work, the role of functional groups (e.g., −COOH and −CF2 groups) in hydrophilic and hydrophobic polymeric binders on the CO2RR of Cu-based catalysts is investigated using a combination of electrochemical measurements, in situ characterization, and density functional theory (DFT) calculations. DFT results reveal that functional groups influence the binding energies of key intermediates involved in both CO2RR and the competing hydrogen evolution reaction, consistent with experimental observation of binder-dependent product distributions among formic acid, CO, CH4, and H2. This study provides a fundamental understanding that the selection of desired polymeric binders is a useful strategy for tuning the CO2RR activity and selectivity.

Transition metal carbides and nitrides are interesting non-precious materials that have been shown to replace or reduce the loading of precious metals for catalyzing several important electrochemical reactions. The purpose of this review is to summarize density functional theory (DFT) studies, describe reaction pathways, identify activity and selectivity descriptors, and present a future outlook in designing carbide and nitride catalysts for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), nitrogen reduction reaction (N2RR), CO2 reduction reaction (CO2RR) and alcohol oxidation reactions. This topic is of high interest to scientific communities working in the field of electrocatalysis and this review should provide theoretical guidance for the rational design of improved carbide and nitride electrocatalysts.

A greenhouse gas and mild oxidant, CO2 can effect the oxidative dehydrogenation (CO2-ODH) of light alkanes over heterogeneous catalysts. These catalysts are bifunctional in that they mediate CO2 reduction while oxidizing the alkanes, most notably the C2–C4 components in shale gas. In this way, one obtains CO and alkenes as value-added products. Although desirable, this transformation has proven challenging in terms of catalyst design, with most catalysts for the CO2-ODH being metal oxides that typically undergo rapid deactivation. More recently, bimetallic catalysts have been identified as promising systems to activate alkanes by either selectively cleaving C–H bonds to produce alkenes or breaking all the C–C and C–H bonds to produce the dry reforming products CO and H2. This Review describes general trends in the CO2-ODH of light alkanes. We will also outline how to use a combined approach involving flow reactor experiments, in operando characterization and density functional theory to determine whether a catalyst is intrinsically active for CO2-ODH or dry reforming. CO2 reacts with alkanes over heterogeneous catalysts to give CO, H2O and the corresponding alkene. This Review describes catalytic bimetallics and their oxides, as well as experimental and theoretical studies of their mechanisms.

The electrochemical carbon dioxide reduction reaction to syngas with controlled CO/H2 ratios has been studied on Pd-based bimetallic hydrides using a combination of in situ characterization and density functional theory calculations. When compared with pure Pd hydride, the bimetallic Pd hydride formation occurs at more negative potentials for Pd-Ag, Pd-Cu, and Pd-Ni. Theoretical calculations show that the choice of the second metal has a more significant effect on the adsorption strength of *H than *HOCO, with the free energies between these two key intermediates (i.e., ΔG(*H)–ΔG(*HOCO)) correlating well with the carbon dioxide reduction reaction activity and selectivity observed in the experiments, and thus can be used as a descriptor to search for other bimetallic catalysts. The results also demonstrate the possibility of alloying Pd with non-precious transition metals to promote the electrochemical conversion of CO2 to syngas. Converting solar energy to hydrogen fuel requires light-absorbers that well-match the wavelengths of incoming sunlight. Here, authors prepare a broadband visible-light-absorbing molecular complex that efficiently produces hydrogen from water.

Ethanol is a green, sustainable, and high-energy-density liquid fuel that holds great promise for direct liquid fuel cells (DLFCs). However, it remains highly challenging to develop electrocatalyst...

Electrochemical conversion of carbon dioxide (CO2) to value-added chemicals has attracted much attention in recent years as a potential alternative to fossil resources. Although significant works h...

CO2 hydrogenation over ZrO2-supported NiFe catalysts is investigated to illustrate the role of Fe in controlling the activity and selectivity, and to reveal the structure-function relationship between metal-oxide interfaces and catalytic selectivities. The Ni-ZrO2 interfaces and Ni-FeOx interfaces are identified as the most likely active sites for the methanation reaction and the reverse water-gas shift reaction, respectively, using combined in-situ and ex-situ characterization techniques. The reaction mechanisms of CO2 hydrogenation to CH4 on the Ni-ZrO2 interfacial sites and to CO on the Ni-FeOx interfacial sites are further revealed by combined in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT) calculations. Both experimental and theoretical results demonstrate that the binding energy of absorbed CO (*CO) is a key descriptor to predict CO2 hydrogenation selectivity: weak interaction (e.g., Ni-FeOx interfaces) promotes *CO desorption to increase CO selectivity, while moderate interaction (e.g., Ni-ZrO2 interfaces) facilitates further hydrogenation of *CO to produce CH4.

Electrochemical CO2 reduction reaction (CO2 RR) with renewable electricity is a potentially sustainable method to reduce CO2 emissions. Palladium supported on cost-effective transition-metal carbides (TMCs) are studied to reduce the Pd usage and tune the activity and selectivity of the CO2 RR to produce synthesis gas, using a combined approach of studying thin films and practical powder catalysts, in situ characterization, and density functional theory (DFT) calculations. Notably, Pd/TaC exhibits higher CO2 RR activity, stability and CO Faradaic efficiency than those of commercial Pd/C while significantly reducing the Pd loading. In situ measurements confirm the transformation of Pd into hydride (PdH) under the CO2 RR environment. DFT calculations reveal that the TMC substrates modify the binding energies of key intermediates on supported PdH. This work suggests the prospect of using TMCs as low-cost and stable substrates to support and modify Pd for enhanced CO2 RR activity.

The synergistic interaction among different components in complex catalysts is one of the crucial factors in determining catalytic performance. Here we report the interactions among the three components in controlling the catalytic performance of Cu–ZnO–ZrO2 (CZZ) catalyst for CO2 hydrogenation to methanol. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements under the activity test pressure (3 MPa) reveal that the CO2 hydrogenation to methanol on the CZZ catalysts follows the formate pathway. Density functional theory (DFT) calculations agree with the in situ DRIFTS measurements, showing that the ZnO–ZrO2 interfaces are the active sites for CO2 adsorption and conversion, while the presence of metallic Cu is also necessary to facilitate H2 dissociation and to provide hydrogen resource. The combined experiment and DFT results reveal that tuning the interaction between ZnO and ZrO2 can be considered as another important factor for designing high performance catalysts for methanol generation from CO2., Despite great efforts, the reaction mechanism of CO2 hydrogenation to methanol and the nature of the active sites on Cu–ZnO–ZrO2 (CZZ) catalysts are still under debate. Herein, the authors report the interactions among the three components in controlling the catalytic performance of CZZ catalyst for CO2 hydrogenation to methanol.

Electrifying chemical manufacturing using renewable energy is an attractive approach to reduce the dependence on fossil energy sources in chemical industries. Primary amines are important organic building blocks; however, the synthesis is often hindered by the poor selectivity because of the formation of secondary and tertiary amine byproducts. Herein, we report an electrocatalytic route to produce ethylamine selectively through an electroreduction of acetonitrile at ambient temperature and pressure. Among all the electrocatalysts, Cu nanoparticles exhibit the highest ethylamine Faradaic efficiency (~96%) at −0.29 V versus reversible hydrogen electrode. Under optimal conditions, we achieve an ethylamine partial current density of 846 mA cm−2. A 20-hour stable performance is demonstrated on Cu at 100 mA cm−2 with an 86% ethylamine Faradaic efficiency. Moreover, the reaction mechanism is investigated by computational study, which suggests the high ethylamine selectivity on Cu is due to the moderate binding affinity for the reaction intermediates., Industrial synthesis of primary amine often features poor selectivity because of the formation of secondary and tertiary amine byproducts. Here, the authors report an electrocatalytic route to ethylamine through selective electroreduction of acetonitrile at ambient temperature and pressure.

The electrochemical CO

Reacting CO2 and ethane to synthesize value-added oxygenate molecules represents opportunities to simultaneously reduce CO2 emissions and upgrade underutilized ethane in shale gas. Herein, we propose a strategy to produce C3 oxygenates using a tandem reactor. This strategy is achieved with a Fe3Ni1/CeO2 catalyst (first reactor at 600–800 °C) for CO2-assisted dehydrogenation and reforming of ethane to produce ethylene, CO, and H2, and a RhCox/MCM-41 catalyst (second reactor at 200 °C) enabling CO insertion for the production of C3 oxygenates (propanal and 1-propanol) via the heterogeneous hydroformylation reaction at ambient pressure. In-situ characterization using synchrotron spectroscopies and density functional theory (DFT) calculations reveal the effect of Rh–Co bimetallic formation in facilitating the production of C3 oxygenates. The proposed strategy provides an opportunity for upgrading light alkanes in shale gas by reacting with CO2 to produce aldehydes and alcohols. Reacting CO2 and ethane to achieve value-added C3 oxygenates offers opportunities to simultaneously reduce CO2 emissions and upgrade underutilized ethane in shale gas. Here, the authors report a successful oxygenate production strategy enabled by inserting CO2-derived CO into ethane-derived ethylene using a tandem reactor.

Dry reforming of methane provides opportunities of using CH4 and CO2 to produce syngas. The PtCo/CeO2 bimetallic catalyst shows higher activity and H2/CO ratio than the corresponding monometallic catalysts, mainly attributed to the synergistic effect of Pt-Co. Structural feature of the PtCo/CeO2 catalyst was revealed by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) of adsorbed CO and in situ techniques like X-ray diffraction (XRD), X-ray adsorption fine structure (XAFS) and ambient-pressure X-ray photoelectron spectroscopy (AP-XPS). Pt-Co alloy and separated Co particles co-existed in the bimetallic catalyst, whereas the former was determined as the dominant active structure with a Pt-Co-mixed-surface termination. During reaction, Pt and Co in the alloy structure nearly maintained their metallic state with slight oxygen decoration, yielding oxygen-metal site-pairs (O*-*). Combined kinetic investigations and DFT calculations reveal that the O*-modified catalytic surface of PtCo/CeO2 promotes C H bond activation with higher entropy contribution (less constraints) to compensate its higher activation barrier. Thermogravimetric analysis (TGA), transmission electron microscope (TEM) and Raman spectroscopy show that the PtCo/CeO2 catalyst is resistant to coke formation as effectively as Pt/CeO2 and can be easily regenerated by a mild CO2 treatment.

Renewable production of ammonia, a building block for most fertilizers, via the electrochemical nitrogen reduction reaction (ENRR) is desirable; however, a selective electrocatalyst is lacking. Here we show that vanadium nitride (VN) nanoparticles are active, selective, and stable ENRR catalysts with an ENRR rate and a Faradaic efficiency (FE) of 3.3 × 10

The oxidative dehydrogenation of n-butane to 1,3-butadiene using CO2 as a soft oxidant is investigated over oxide-supported NiFe bimetallic catalysts. Dry reforming of n-butane with CO2 to syngas is also studied under identical conditions for comparison. The Ni1Fe3/CeO2 catalyst is identified as a promising catalyst for the oxidative dehydrogenation to 1,3-butadiene via the C H bond cleavage, while the Ni3Fe1/CeO2 catalyst mainly promotes the dry reforming pathway via the C C bond scission. The oxidation states of Ni and Fe are determined by X-ray absorption fine structure (XAFS) measurements under reaction conditions. Density functional theory (DFT) calculations are performed to further understand the different reaction pathways. Furthermore, the effect of oxide supports is studied for the Ni1Fe3 bimetallic catalysts, showing that highly reducible supports, CeO2 and CeO2-ZrO2, promote the production of 1,3-butadiene, whereas the ZrO2 support significantly suppresses the oxidative dehydrogenation.

Tungsten carbide modified nickel (Ni-WC/C) catalyst is synthesized through the sequential impregnation method and evaluated for the electrooxidation of urea in alkaline electrolyte. Both the activity and stability of Ni are enhanced by the introduction of WC. In situ Fourier transform infrared (FTIR) measurements combined with electrochemical analysis were used to provide a better understanding of the mechanism for urea electrooxidation on the Ni-based catalysts. The formation of CO2 and NCO− species is detected during urea oxidation, and the synergistic effect resulting from the interaction of Ni and WC is also proposed. The Ni-WC/C electrode contributes to the improved C–N bond cleavage in urea than that on Ni/C, resulting in a higher activity. Furthermore, the introduction of WC also enhances the anti-poisoning ability, thus promoting more complete oxidation of urea to produce CO2, which leads to a higher energy conversion efficiency than that on Ni/C. This work provides a new strategy for designing highly efficient catalysts for urea electrooxidation.

Bimetallic Pt3Co alloys are the commercial electrocatalysts for the oxygen reduction reaction in a fuel cell, but their high Pt loading and durability are a concern. Working toward the goal of redu...

Ethylene (C2H4) is one of the most important raw materials for chemical industry. The tandem reactions of CO2-assisted dehydrogenation of ethane (C2H6) to ethylene creates an opportunity to effectively use the underutilized ethane from shale gas while mitigating anthropogenic CO2 emissions. Here we identify the most likely active sites over CeO2-supported NiFe catalysts by using combined in situ characterization with density-functional theory (DFT) calculations. The experimental and theoretical results reveal that the Ni–FeOx interfacial sites can selectively break the C–H bonds and preserve the C–C bond of C2H6 to produce ethylene, while the Ni–CeOx interfacial sites efficiently cleave all of the C–H and C–C bonds to produce synthesis gas. Controlled synthesis of the two distinct active sites enables rational enhancement of the ethylene selectivity for the CO2-assisted dehydrogenation of ethane.

Pt-based materials are the most efficient catalysts for the oxygen reduction reaction (ORR) in proton-exchange membrane fuel cells. However, fabrication of active and stable Pt catalysts still remains challenging. In this work, Pt-l-phenylalanine (Pt-LPHE) films, with highly dispersed Pt nanoparticles (NPs) featuring predominately (111) facets, have been prepared via a room-temperature electron reduction method. Loading Pt-LPHE onto carbon support produces a novel nanomaterial (Pt-AL/C), resulting in a simultaneous loading of highly dispersed Pt NPs and N doping. Density functional theory calculations demonstrate that the N dopants stabilize the Pt NPs and reduce the *O/*OH binding energies on the Pt NPs. As a result, the Pt-AL/C nanomaterial shows significantly enhanced ORR activity and stability over commercial Pt/C after 10 000 cycle stability tests. This work provides a novel eco-friendly and energy-neutral approach for preparing metal NPs with controllable structures and sizes.

The oxygen evolution reaction (OER) has broad applications in electrochemical devices, but it often requires expensive and scarce Ir-based catalysts in acid electrolyte. Presented here is a framework to reduce Ir loading by combining core–shell iridium/metal nitride morphologies using in situ experiments and density functional theory (DFT) calculations. Several group VIII transition metal (Fe, Co, and Ni) nitrides are studied as core materials, with Ir/Fe4N core–shell particles showing enhancement in both OER activity and stability. In situ X-ray absorption fine structure measurements are used to determine the structure and stability of the core–shell catalysts under OER conditions. DFT calculations are used to demonstrate adsorbate binding energies as descriptors of the observed activity trends.

Disorder–Order transitions in a weakly adsorbed two-dimensional film have been identified for the first time using ambient-pressure scanning tunneling microscopy (AP-STM) and X-ray photoelectron spectroscopy (AP-XPS). As of late, great effort has been devoted to the capture, activation and conversion of carbon dioxide (CO2), a ubiquitous greenhouse gas and by-product of many chemical processes. The high stability and non-polar nature of CO2 leads to weak bonding with well-defined surfaces of metals and oxides. CO2 adsorbs molecularly on the rutile TiO2(110) surface with a low adsorption energy of ∼10 kcal mol−1. In spite of this weak binding, images of AP-STM show that a substantial amount of CO2 can reside on a TiO2(110) surface at room temperature forming two-dimensionally ordered films. We have employed microscopic imaging under in situ conditions, soft X-ray spectroscopy and theory to decipher the unique ordering behavior seen for CO2 on TiO2(110).

Ethane (CH3CH3), one of the primary components of shale gas, is an attractive candidate for the production of syngas (CO + H2) and ethylene (CH2CH2) via the selective C–C and C–H bond cleavage, respectively. Understanding the origin of the selective conversion is essential to the design of a good catalyst for CH3CH3 activation. Herein, we combined density functional theory (DFT) calculations with kinetic Monte Carlo (KMC) simulations to shed light on the mechanism of the oxidative C–H and C–C bond cleavage of CH3CH3 on a PtNi(111) model catalyst using CO2 as an oxidant, where the estimated selectivity is in good agreement with the experimental results on PtNi nanoparticles supported on CeO2. Our calculations show that PtNi is selective to CO via direct CO2 dissociation and the oxidative C–C bond scission of CH3CH3via the oxygenated (*C2HyO) intermediates. By comparison the CH2CH2 selectivity via the selective C–H bond scission of *CH3CH3 is much lower. The kinetic analysis suggests that the selectivity of PtNi toward syngas can be enhanced by facilitating the formation of key *C2HyO intermediates, while the selectivity toward CH2CH2 is promoted mainly by accelerating the C–H bond scission of *CH3CH2 to produce *CH2CH2.

The chemical transformation of CO2 not only mitigates the anthropogenic CO2 emission into the Earth’s atmosphere but also produces carbon compounds that can be used as precursors for the production of chemicals and fuels. The activation and conversion of CO2 can be achieved on multifunctional catalytic sites available at the metal/oxide interface by taking advantage of the synergy between the metal nanoparticles and oxide support. Herein, we look at the recent progress in mechanistic studies of CO2 hydrogenation to C1 (CO, CH3OH, and CH4) compounds on metal/oxide catalysts. On this basis, we are able to provide a better understanding of the complex reaction network, grasp the capability of manipulating structure and combination of metal and oxide at the interface in tuning selectivity, and identify the key descriptors to control the activity and, in particular, the selectivity of catalysts. Finally, we also discuss challenges and future research opportunities for tuning the selective conversion of CO2 on ...

The active sites over commercial copper/zinc oxide/aluminum oxide (Cu/ZnO/Al2O3) catalysts for carbon dioxide (CO2) hydrogenation to methanol, the Zn-Cu bimetallic sites or ZnO-Cu interfacial sites, have recently been the subject of intense debate. We report a direct comparison between the activity of ZnCu and ZnO/Cu model catalysts for methanol synthesis. By combining x-ray photoemission spectroscopy, density functional theory, and kinetic Monte Carlo simulations, we can identify and characterize the reactivity of each catalyst. Both experimental and theoretical results agree that ZnCu undergoes surface oxidation under the reaction conditions so that surface Zn transforms into ZnO and allows ZnCu to reach the activity of ZnO/Cu with the same Zn coverage. Our results highlight a synergy of Cu and ZnO at the interface that facilitates methanol synthesis via formate intermediates.

The electrochemical carbon dioxide reduction reaction (CO2RR) to simultaneously produce carbon monoxide (CO) and hydrogen (H2) has been achieved on carbon supported palladium (Pd/C) nanoparticles in an aqueous electrolyte. The synthesis gas product has a CO to H2 ratio between 0.5 and 1, which is in the desirable range for thermochemical synthesis of methanol and Fischer–Tropsch reactions using existing industrial processes. In situ X-ray absorption spectroscopy in both near-edge (XANES) and extended regions (EXAFS) and in situ X-ray diffraction show that Pd has transformed into β-phase palladium hydride (β-PdH) during the CO2RR. Density functional theory (DFT) calculations demonstrate that the binding energies of both adsorbed CO and H are significantly weakened on PdH than on Pd surfaces, and that these energies are potential descriptors to facilitate the search for more efficient electrocatalysts for syngas production through the CO2RR.

The selective hydrogenation of biomass-derived 2(5H)-furanone to γ-butyrolactone (GBL) was studied over Pt-Ni and Pt-Co bimetallic model surfaces and supported catalysts. The reactions of 2(5H)-furanone were investigated on Ni/Pt(1 1 1) and Co/Pt(1 1 1) bimetallic surfaces using temperature-programmed desorption (TPD), revealing that the Ni-terminated bimetallic Ni-Pt-Pt(1 1 1) surface was more active and selective to produce GBL. Parallel density functional theory (DFT) calculations also confirmed the higher hydrogenation activity on Ni-Pt-Pt(1 1 1) due to bimetallic effect. The promising results on model surfaces were extended to SiO2-supported catalysts. The hydrogenation activity in terms of the initial turnover frequency (TOF) followed the trend of Pt-Ni > Pt-Co > Pt > Ni > Co, where the TOF over Pt-Ni was almost twice higher than that over Pt. With the excellent correlation between model surfaces and supported catalysts, the Pt-Ni bimetallic catalyst was identified as a promising option for the selective hydrogenation of 2(5H)-furanone to GBL.

The electrochemical CO

Electrochemical conversion of carbon dioxide (CO

Despite recent intense interest in the development of catalysts for the electrochemical nitrogen reduction reaction (ENRR), mechanistic understanding and catalyst design principles remain lacking. In this work, we develop a strategy to determine the density of initial and steady-state active sites on ENRR catalysts that follow the Mars-van Krevelen mechanism via quantitative isotope-exchange experiments. This method allows the comparison of intrinsic activities of active sites and facilitates the identification and improvement of active-site structures for ENRR. Combined with detailed density functional theory calculations, we show that the rate-limiting step in the ENRR is likely the initial N≡N bond activation via the addition of a proton and an electron to the adsorbed N2 on the N vacancies to form N2 H. The methodology developed and mechanistic insights gained in this work could guide the rational catalyst design in the ENRR.

The electrochemical carbon dioxide reduction reaction to syngas with controlled CO/H2 ratios has been studied on Pd-based bimetallic hydrides using a combination of in situ characterization and density functional theory calculations. When compared with pure Pd hydride, the bimetallic Pd hydride formation occurs at more negative potentials for Pd-Ag, Pd-Cu, and Pd-Ni. Theoretical calculations show that the choice of the second metal has a more significant effect on the adsorption strength of *H than *HOCO, with the free energies between these two key intermediates (i.e., ΔG(*H)–ΔG(*HOCO)) correlating well with the carbon dioxide reduction reaction activity and selectivity observed in the experiments, and thus can be used as a descriptor to search for other bimetallic catalysts. The results also demonstrate the possibility of alloying Pd with non-precious transition metals to promote the electrochemical conversion of CO2 to syngas., Converting solar energy to hydrogen fuel requires light-absorbers that well-match the wavelengths of incoming sunlight. Here, authors prepare a broadband visible-light-absorbing molecular complex that efficiently produces hydrogen from water.