mA Mg-1 Research Articles

Effects of pores structure of MgO-templated combined with KOH active porous carbon on its supported Pt catalysts for enhanced electrocatalytic reactions

Pore structures in carbon materials have been referred to regulate the properties of carbon, which are meaningful for improving electro-catalytic performance. Herein, a series of Pt-based porous carbon catalysts (Pt/MPC) are synthesized, which are used in hydrogen evolution reaction (HER), oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR). The coupling of template method and KOH activation is used to synthesize carbon carrier, then Pt NPs are loaded on it by NaBH4 reduction. The well-tuned catalyst Pt/MPC(131) exhibits an overpotential of 34 mV and 23 mV at the current density of 10 mA cm-2 in 1 M KOH and 0.5 M H2SO4 for HER (under 5.76 wt.% Pt load), respectively. The micropore regulated by KOH provides a high ion-accessible surface, and mesoporous formed by MgO template provide a fast channel for ion transport, which leads to great electron transport and increased exposure of Pt. Besides, the MOR activity of Pt/MPC(131) is 1932.05 mA mg-1, which is 2.68 times higher than that of commercial 20%Pt/C (721.14 mA mg-1), and has half-wave potential of 0.82 V on ORR. The abundant hierarchical pores and highly utilized Pt active sites are favorable for accelerating the sluggish kinetics of HER, MOR, and ORR. This work provides an anticipated perspective of applicable Pt-based catalyst for advanced electrocatalysts.

Ni- and Co-Based MOF-Derived NixCo3-xO4 Materials: As an Efficient Anode for Direct Methanol Fuel Cell Application.

Finding inexpensive and efficient anode materials is crucial for the oxidation of methanol in the direct methanol fuel cell (DMFC), which is the key electrode reaction. Herein, we report metal-organic framework (MOF)-derived Co3O4, NiO, and NixCo3-xO4 (where x = 1.5, 1, and 0.6) materials deposited on nickel foam as efficient anode material for methanol oxidation. Among them, NiCo2O4 exhibited the highest methanol oxidation activity, owing to its lowest charge-transfer resistance (0.097 Ω) and high electrochemically active surface area (1950 cm2), resulting in the lowest onset potential of 0.35 V vs Hg/HgO. The optimized Ni-to-Co ratio and synergistic effect between Ni and Co metals enable NiCo2O4 to achieve the highest mass activity of 151 mA mg-1 and geometric current density of 288 mA cm-2, demonstrating excellent durability over 14 h at 0.6 V. In addition, to optimize methanol concentration, all the electrocatalysts were tested in a range of methanol concentrations, showing 0.5 M methanol as the optimal concentration. This study focuses on optimizing the metal ratio and methanol concentration to achieve the highest catalytic activity. Additionally, this lays the foundation for developing diverse MOF-derived electrocatalysts and advancing DMFCs.

Harnessing the Potential of Hollow Graphitic Carbon Nanocages for Enhanced Methanol Oxidation Using PtRu Nanoparticles.

Direct Methanol Fuel Cell (DMFC) is a powerful system for generating electrical energy for various applications. However, there are several limitations that hinder the commercialization of DMFCs, such as the expense of platinum (Pt) at market price, sluggish methanol oxidation reaction (MOR) due to carbon monoxide (CO) formation, and slow electrooxidation kinetics. This work introduces carbon nanocages (CNCs) that were obtained through the pyrolysis of polypyrrole (Ppy) as the carbon source. The CNCs were characterized using BET, XRD, HRTEM, TEM, SEM, and FTIR techniques. The CNCs derived from the Ppy source, pyrolyzed at 750 °C, exhibited the best morphologies with a high specific surface area of 416 m2g-1, allowing for good metal dispersion. Subsequently, PtRu catalyst was doped onto the CNC-Ppy750 support using chemical reduction and microwave-assisted methods. In electrochemical tests, the PtRu/CNC-Ppy750 electrocatalyst demonstrated improved CO tolerance and higher performance in MOR compared to PtRu-supported commercial carbon black (CB), with values of 427 mA mg-1 and 248 mA mg-1, respectively. The superior MOR performance of PtRu/CNC-Ppy750 was attributed to its high surface area of CNC support, uniform dispersion of PtRu catalyst, and small PtRu nanoparticles on the CNC. In DMFC single-cell tests, the PtRu/CNC-Ppy750 exhibited higher performance, approximately 1.7 times higher than PtRu/CB. In conclusion, the PtRu/CNC-PPy750 represents a promising electrocatalyst candidate for MOR and anodic DMFC applications.

Morphology Variation of Ternary PdCuSn Nanocrystalline Assemblies and Their Electrocatalytic Oxidation of Alcohols.

Metal alloys not only increase the composition and spatial distribution of elements but also provide the opportunity to adjust their physicochemical properties. Recently, multimetallic alloy nanocatalysts have attracted great attention in energy applications and the chemical industry. This work presents the production of three ternary PdCuSn nanocrystalline assemblies with similar compositions via a one-step hydrothermal method. The shape variation of assembly units from nanosheets and nanowires to nanoparticles were realized by adjusting the percentage of Sn in metal precursors. Experimental data show that PdCuSn nanowire networks showed the best catalytic activity by virtue of their optimized morphological characteristics and microscopic electronic structure. With electrooxidation of methanol, ethanol, ethylene glycol, and glycerol at 30 °C, PdCuSn nanowire networks demonstrated catalytic activity of 1129, 2111, 2540, and 1445 mA mg-1, respectively. The catalytic activity for alcohol oxidation is attributed to the production of the electronic structure and morphology features that are most suitable. This is achieved by introducing the proper quantities of Cu and Sn components in the first stage of synthesis. This study would help with the construction of high-efficiency nanostructured alloy catalysts by regulating the electronic structure and morphology.

Ultra-Large Two-Dimensional Metal Nanowire Networks by Microfluidic Laminar Flow Synthesis for Formic Acid Electrooxidation.

Despite the great research interest in two-dimensional metal nanowire networks (2D MNWNs) due to their large specific surface area and abundance of unsaturated coordination atoms, their controllable synthesis still remains a significant challenge. Herein, a microfluidics laminar flow-based approach is developed, enabling the facile preparation of large-scale 2D structures with diverse alloy compositions, such as PtBi, AuBi, PdBi, PtPdBi, and PtAuCu alloys. Remarkably, these 2D MNWNs can reach sizes up to submillimeter scale (~220 μm), which is significantly larger than the evolution from the 1D or 3D counterparts that typically measure only tens of nanometers. The PdBi 2D MNWNs affords the highest specific activity for formic acid (2669.1 mA mg-1) among current unsupported catalysts, which is 103.5 times higher than Pt-black, respectively. Furthermore, in situ Fourier transform infrared (FTIR) experiments provide comprehensive evidence that PdBi 2D MNWNs catalysts can effectively prevent CO* poisoning, resulting in exceptional activity and stability for the oxidation of formic acid.

Modulating the Energy Barrier via the Synergism of Cu3P and CoP to Accelerate Kinetics for Bolstering Oxygen Electrocatalysis in Zn-Air Batteries.

Modulating the energy barrier of reaction intermediates to surmount sluggish kinetics is an utterly intriguing strategy for amplifying the oxygen reduction reaction. Herein, a Cu3P/CoP hybrid is incorporated on hollow porous N-doped carbon nanospheres via dopamine self-polymerization and high-temperature treatment. The resultant Cu3P/CoP@NC showcases a favorable mass activity of 4.41 mA mg-1 and a kinetic current density of 2.38 mA cm-2. Strikingly, the catalyst endows the aqueous Zn-air battery (ZAB) with a large power density of 209.0 mW cm-2, superb cyclability over 317 h, and promising application prospects in flexible ZAB. Theoretical simulations reveal that Cu functions as a modulator to modify the free energy of intermediates and adsorbs the O2 on the Co sites, hence rushing the reaction kinetics. The open and hydrophilic hollow spherical mesoporous structure provides unimpeded channels for reactant diffusion and electrolyte penetration, whereas the exposed inner and outer surfaces can confer a plethora of accessible actives sites. This research establishes a feasible design concept to tune catalytic activity for non-noble metal materials by construction of a rational nanoframework.

Engineering of Pt@Ni,N-doped graphene electrocatalyst based on recycled water bottles waste as an efficient cathode material for PEM fuel cells

Fuel cells (FCs) represent one of the most promising clean power sources. Their cost represents a considerable challenge to their widespread commercialization because of their sensitivity and the expensive cost of the employed platinum electrocatalysts. Accordingly, one feature of a fuel cell device that many interested parties are looking for is the engineering of catalysts with a low Pt content. Herewith, Pt supported on nickel loaded nitrogen-doped graphene (Pt@Ni,N-G) was synthesized through a simple pyrolysis process of mineral water bottles waste with urea and nickel metal at 800 °C followed by loading Pt in different proportions via a simple reduction method in aqueous solution at room temperature. The physicochemical and electrochemical properties of a promising Pt@Ni,N-G cathode electrocatalyst for polymer electrolyte membrane fuel cell (PEMFC) were characterized and evaluated using a number of specialized techniques. The results showed that the high Pt@Ni,N-G content enhanced the catalytic activity of the oxygen reduction reaction (ORR), with a specific activity of 3.13 mA cm−2 and a mass activity of 12.35 mA μg−1Pt at −0.1 V. A maximum power density of 87.8 mW cm−2 was achieved which is closest to that of commercial Pt/C. Designing Pt@Ni,N-G electrocatalysts by recycling waste bottles is not only expected to reduce the cost of fuel cells by ~30 % to raise the industry standard but also protect the environment and humanity from harmful pollutants.

Synthesis of Monodispersed Pd Nanoparticles and Ultrathin Twisty Pd Nanowire Networks for Electrooxidation of Ethanol.

In recent years, preparing precious metal catalysts with a controllable morphology has become a hot research topic for researchers. In this study, monodispersed palladium (Pd) nanoparticles (NP) and ultrathin Pd twisty nanowire networks (TNN) were synthesized in a solvothermal system using N,N-dimethylformamide (DMF) and oleylamine (OAm) as solvents, Transmission electron microscopy (TEM) images reveal the successful synthesis of nanoparticles and ultrathin TNN microstructures. Electrochemical data show that the current densities of Pd-NP and Pd-TNN for the ethanol oxidation reaction (EOR) reach 1878 mA mg-1 and 1765 mA mg-1, respectively. Compared to commercial Pd/C, Pd-TNN and Pd-NP exhibit better catalytic stability, lower electron transfer barriers, and more resistance to catalyst poisoning. Temperature, pH value, and ethanol concentration are all favorable for the EOR. According to the experimental data, the mechanism of enhanced electrocatalytic activity of Pd-NP and Pd-TNN catalysts for ethanol oxidation is discussed. This paper presents a method for preparing catalysts with stabilized structures to develop Pd-based catalysts for electrocatalytic oxidation reactions.

Tuning the Structure of Pd@Ni-Co Nanowires and Their Electrochemical Properties.

One-dimensional transition metal materials are promising supports for precious metals used in energy production processes. Due to their electrochemical properties, 3d-group metals (such as Ni, Co, and Fe) can actively interact with catalysts by a strong metal-support interaction. This study shows that changing the Ni:Co ratio makes it possible to modulate the structure of the catalyst supports, which, in turn, provides a tool for designing their electrical and electrochemical properties. For example, Ni1-Co9 shows the highest electrical conductivity (5.8-10-4 S/cm) among all of the materials examined. On the contrary, the Pd@Ni7-Co3 system presents the highest mass activity (>2000 mA mg-1) at 0.7 V, exceeding by several times that of commercial Pt/C (>300 mA mg-1) at the same potential. Our study opens the gateway for applications of bimetallic transition metal nanowires in catalytic conversion and energy production processes.

Temperature-Induced Interface Hybridization of WC Boosts NiCu Activity for Alkaline Hydrogen Oxidation Reaction.

The development of non-precious hydrogen oxidation reaction (HOR) catalysts is a major challenge for the commercialization of Pt-free fuel cells. Herein, a temperature-induced phase hybridization method is reported that greatly improves the catalytic performance of NiCu alloy for the HOR. The migration of W atoms hybridizes the interface of tungsten oxide (WOx) and tungsten carbide (WC) at the onset reduction temperature of WOx, leading to a greatly weakened H binding energy and an optimized OH binding energy, which endows NiCuW/WOx-WC@WC with favorable stability and CO resistance during HOR. The hybridization catalysts deliver a high mass activity of 29.37 mA mg-1 Ni and reach a peak power of 298 mW.cm-2 in H2-O2 anion exchange membrane fuel cells (AEMFCs).

Hierarchical PtCuMnP Nanoalloy for Efficient Hydrogen Evolution and Methanol Oxidation.

The higher amount of Pt usage and its poisoning in methanol oxidation reaction in acidic media is a major setback for methanol fuel cells. Herein, a promising dual application high-performance electrocatalyst has been developed for hydrogen evolution and methanol oxidation. A low Pt-content nanoalloy co-doped with Cu, Mn, and P is synthesized using a modified solvothermal process. Initially, ultrasmall ≈2.9 nm PtCuMnP nanoalloy is prepared on N-doped graphene-oxide support and subsequently, it is characterized using several analytical techniques and examined through electrochemical tests. Electrochemical results show that PtCuMnP/N-rGO has a low overpotential of 6.5 mV at 10 mA cm-2 in 0.3m H2SO4 and high mass activity for the hydrogen evolution reaction. For the methanol oxidation reaction, the PtCuMnP/N-rGO electrocatalyst exhibits robust performance. The mass activity of PtCuMnP/N-rGO is 6.790mA mg-1 Pt, which is 7.43 times higher than that of commercial Pt/C (20% Pt). Moreover, in the chronoamperometry test, PtCuMnP/N-rGO shows exceptionally good stability and retains 72% of the initial current density even after 20,000 cycles. Furthermore, the PtCuMnP/N-rGO electrocatalyst exhibits outstanding performance for hydrogen evolution and methanol oxidation along with excellent anti-poisoning ability. Hence, the developed bifunctional electrocatalyst can be used efficiently for hydrogen evolution and methanol oxidation.

Activating and Identifying the Active Site of RuS2 for Alkaline Hydrogen Oxidation Electrocatalysis

AbstractSearching for highly efficient and economical electrocatalysts for alkaline hydrogen oxidation reaction (HOR) is crucial for the development of alkaline polymer membrane fuel cells. Here, we report a valid strategy to active pyrite‐type RuS2 for alkaline HOR electrocatalysis by introducing sulfur vacancies. The obtained S‐vacancies modified RuS2−x exhibits outperformed HOR activity with a current density of 0.676 mA cm−2 and mass activity of 1.43 mA μg−1, which are 15‐fold and 40‐fold improvement than those of Ru catalyst. In situ Raman spectra demonstrate the formation of S−H bond during the HOR process, identifying the S atom of RuS2−x is the real active site for HOR catalysis. Density functional theory calculations and experimental results including in situ surface‐enhanced infrared absorption spectroscopy suggest the introduction of S vacancies can rationally modify the p orbital of S atoms, leading to enhanced binding strength between the S sites and H atoms on the surface of RuS2−x, together with the promoted connectivity of hydrogen‐bonding network and lowered water formation energy, contributes to the enhanced HOR performance.

Carbon nanotube-bridged MXene nanoarchitectures decorated with ultrasmall Rh nanoparticles for efficient methanol oxidation

Rational design and precise synthesis of cost-effective and highly-active Pt-alternative anode catalysts are important paths to accelerate the application and promotion of direct methanol fuel cell. Herein, a robust and controllable synthetic strategy is developed to bottom-up construction of carbon nanotube-bridged Ti3C2Tx MXene nanoarchitectures decorated with ultrasmall Rh nanoparticles (denoted as Rh/CNT-MX) through a facile co-assembly process. The existence of MXene nanosheets with abundant anchoring sites can immobilize nano-sized Rh crystals and facilitate their dispersion, while the integration of CNT skeletons effectively separates the neighboring MXene layers and offers unimpeded electron transport channels, which are conducive to making full use of respective catalytic functions for each component. As a consequence, the optimized Rh/CNT-MX catalyst expresses superior methanol oxidation performance with a considerable electrochemically active surface area of 89.4 m2/g, high mass/specific activity of 911.0 mA/mg/1.02 mA/cm2, and reliable long-term durability, which has obvious competitive advantages over the conventional Rh/carbon black, Rh/CNT, Rh/MXene, as well as commercial Pt/carbon black and Pd/carbon black catalysts.

A sol-gel derived LaCoO3 perovskite as an electrocatalyst for Al-air batteries.

In this work, we report the performance of the LaCoO3 perovskite oxide as a cathode catalyst for an Al-air battery. LaCoO3 was prepared using the sol-gel method and its suitability as a catalyst has been studied. XRD studies of the perovskite revealed a monoclinic symmetry with no secondary phase being observed. An aggregated morphology with a porous structure was observed from SEM analysis. TEM studies showed that the aggregated LaCoO3 particles exhibited an average diameter of 49.94 nm. The surface area obtained using the BET method is found to be 9.088 m2 g-1. The electrochemical activity of LaCoO3 towards the oxygen reduction reaction (ORR) was higher than that of the bare glassy carbon electrode (GCE). From the kinetic studies, the number of electrons transferred was found to be 4.08, indicating that the reaction occurs through a 4e- pathway. The mass activity and specific activity were found to be 3.05 mA mg-1 and 0.33 mA cm-2 at 1.2 V (vs. the reversible hydrogen electrode (RHE)), respectively. The stability of LaCoO3 was studied using chronoamperometry and impedance analyses, which revealed less charge transfer resistance before and after the stability test. Subsequently, an Al-air battery was fabricated using LaCoO3 as the cathode and Al as the anode. Polyvinyl alcohol (PVA) based KOH gel was used as an electrolyte. The cell exhibited an open circuit voltage (OCV) of 1.35 V with a discharging capacity of 1770 mA h g-1. In addition, the power density was calculated to be 10.04 mW cm-2 at 0.6 V vs. RHE. Our studies suggest that LaCoO3 can be a promising candidate as a cathode for high-performance Al-air batteries.

Constructing Fully-Active and Ultra-Active Sites in High-Entropy Alloy Nanoclusters for Hydrazine Oxidation-Assisted Electrolytic Hydrogen Production.

The development of sufficiently high-efficiency systems and effective catalysts for electrocatalytic hydrogen production is of great significance but challenging. Here, high-entropy alloy nanoclusters (HEANCs) with full-active sites and super-active sites are innovatively constructed for hydrazine oxidation-assisted electrolytic hydrogen production. The HEANCs show an average size of only seven atomic layers (1.48nm). As the catalysts for both hydrogen evolution reaction (HER) and hydrazine oxidation reaction, the HEANC/C exhibits the best-level performance among reported electrocatalysts. Especially, the HEANC/C achieves an ultrahigh mass activity of 12.85 A mg-1 noble metals at -0.07V and overpotential of only 9.5mV for 10mA cm-2 for alkaline HER. Further, with HEANC/C as both anode and cathode catalysts, an overall hydrazine oxidation-assisted splitting (OHzS) electrolyzer shows a record mass activity of 250.2mA mg-1 catalysts at 0.1V and only requires working voltages of 0.025 and 0.181V to reach 10 and 100mA cm-2, respectively, outperforming those of overall water-splitting system and other reported chemicals-assisted hydrogen production systems. Active site libraries including 72 sites on HEANC surface are originally constructed by theoretical calculations, revealing that all sites on HEANC surface are effective active sites for OHzS; especially some are super-active sites, endowing the best-level performance of HEANC/C.

Sheet-Isolated MoS2 Used for Dispersing Pt Nanoparticles and its Application in Methanol Fuel Cells.

It is highly challenging to activate the basal plane and minimize the π-π stacking of MoS2 sheets, thus enhancing its catalytic performance. Here, we display an approach for making well-dispersed MoS2 . By using the N-doped multi-walled carbon nanotubes (NMWCNTs) as an isolation unit, the aggregation of MoS2 sheets was effectively reduced, favoring the dispersion of Pt nanoparticles (noted as Pt/NMWCNTs-isolated-MoS2 ). Excellent bifunctional catalytic performance for methanol oxidation and oxygen reduction reaction (MOR/ORR) were demonstrated by the produced Pt/NMWCNTs-isolated-MoS2 . In comparison to Pt nanoparticles supported on MoS2 (Pt/MoS2 ), the MOR activity (2314.14 mA mgpt -1 ) and stability (317.69 mA mgpt -1 after 2 h of operation) on Pt/NMWCNTs-isolatedMoS2 were 24 and 232 times higher, respectively. As for ORR, Pt/NMWCNTs-isolated-MoS2 holds large half-wave potential (0.88 V) and high stability (92.71 % after 22 h of operation). This work presents a tactic for activating the basal planes and reducing the π-π stacking of 2D materials to satisfy their applications in electrocatalysis. In addition, the proposed sheet-isolation method can be used for fabricating other 2D materials to promote the dispersion of nanoparticles, which assist its application in other fields of energy as well as the environment.

Anchoring Ultrasmall Pt Nanocrystals onto Carbon Nanohorn-Decorated 3D Graphene Networks to Boost Methanol Oxidation Reaction

The successful commercialization of the direct methanol fuel cell (DMFC) is inseparable from the development of advanced Pt-based anode catalysts with high electrocatalytic activity and acceptable manufacturing cost. Here, we present a robust bottom-up strategy to anchor ultrasmall Pt nanocrystals with an average diameter of only 2.3 nm onto carbon nanohorn-decorated three-dimensional (3D) graphene networks (Pt/CNH-G) through a controllable self-assembly process. The as-derived 3D Pt/CNH-G catalysts manifest a series of distinctive architectural advantages, such as interconnected porous frameworks, large accessible surface areas, plentiful active cones, highly dispersed Pt nanoparticles, and good electron conductivity. Consequently, the optimized Pt/CNH-G catalyst is endowed with exceptional methanol oxidation properties with a large electrochemical active surface area of 128.6 m2 g-1, a high mass activity of 1626.0 mA mg-1, and excellent long-term stability, which are significantly superior to those of conventional Pt catalysts supported by carbon black, carbon nanotube, carbon nanohorn, and graphene matrices.

Assembly of Alloyed PdM (Ag, Cu, and Sn) Nanosheets and Their Electrocatalytic Oxidation of Ethanol and Methanol.

Direct alcohol fuel cells are popular due to their high energy density, abundant sources, and ease of transportation and storage. Palladium-based nanosheet self-assembled materials have emerged as an effective catalyst for alcohol oxidation reactions. In this work, nanosheets were synthesized with the same feeding ratio assembly of alloyed PdM (M = Ag, Cu, and Sn). The introduction of the second element was able to enhance the catalytic response of the catalysts to alcohol electrooxidation. Among them, the PdCu alloy exhibited the best performance in terms of catalytic activity, toxicity resistance, and stability to ethanol oxidation reaction (EOR) and methanol oxidation reaction (MOR). The catalytic current densities for EOR can reach 2226, 2518, and 1598 mA mg-1 for PdAg, PdCu, and PdSn nanosheet assemblies, respectively. These are mainly attributed to better electronic effects, altered atomic distances within the cell for the d-band centers of Pd, and a larger electrochemical active surface area (ECSA). The optimized d-band center is beneficial to promote the catalytic performance of EOR and MOR. Experimental data also demonstrated that higher electrocatalytic temperature, higher pH, and higher alcohol concentration can accelerate the rate of alcohol electrooxidation. These results have the potential to be extended to Pd-M (M = other metals) nanosheets and help for a wider range of catalytic applications.

Pd Nanoparticle-Decorated Novel Ternary Bi2O2CO3-Bi2MoO6-CuO Heterojunction for Enhanced Photo-electrocatalytic Ethanol Oxidation.

Recently, photo-electrooxidation of fuel using a noble metal-semiconductor junction has been one of the most promising approaches in fuel cell systems. Herein, we report the development of a Pd-supported Bi2MoO6-Bi2O2CO3-CuO novel ternary heterojunction for ethanol oxidation in alkali in the presence and absence of visible light. Various spectroscopic and microscopic characterization techniques confirm strong coupling between palladium nanoparticles and Bi2MoO6-Bi2O2CO3-CuO ternary heterojunction supports. The photo-electrocatalytic efficacy of the synthesized catalysts was inspected by cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). The CV study reveals that the forward peak current density (in mA mg-1 of Pd) of the synthesized quaternary heterojunction was about 1482.5, which is 2.4, 4, and 4.6 times higher than that of Pd/CuO (608.3), Pd/Bi2MoO6-Bi2O2CO3 (368.3), and similarly synthesized Pd catalyst (321.5) under visible light radiation. The best heterojunction catalyst shows 2.21-fold higher peak current density in visible light compared to that in dark. CA study reveals that after operation for 6000 s, the current density of the quaternary electrode is 1.5 and 3.4 times greater than that of Pd/CuO and Pd/C catalysts, respectively. The greater photocurrent response, lower photoluminescence (PL) emission intensity, and smaller semicircle arc in the Nyquist plot of the quaternary catalyst demonstrate the efficient segregation and higher charge transfer conductance of photogenerated charges to facilitate the photo-electrooxidation process of ethanol. The stability test shows that the quaternary catalyst loses only 9.8 and 7.7% of its maximum current density after 500 cycles of CV operation in the dark and light, respectively, indicating that light energy is more beneficial in establishing high stability. The dramatic enhancement of the photo-electrocatalytic activity of the quaternary electrode is owing to the lower band gap, high ECSA, enhanced charge separation of photogenerated carriers (e--h+), and all cocatalytic support of Bi2MoO6, Bi2O2CO3, and CuO in Pd/ Bi2MoO6-Bi2O2CO3-CuO under visible light radiation. The morphology and structure of the used quaternary catalyst are tested using FESEM and PXRD. Finally, ex situ FTIR spectroscopy and HPLC techniques help understand the ethanol electrooxidation reaction mechanism.

Understanding Alkaline Hydrogen Oxidation Reaction on PdNiRuIrRh High‐Entropy‐Alloy by Machine Learning Potential

AbstractHigh‐entropy alloy (HEA) catalysts have been widely studied in electrocatalysis. However, identifying atomic structure of HEA with complex atomic arrangement is challenging, which seriously hinders the fundamental understanding of catalytic mechanism. Here, we report a HEA‐PdNiRuIrRh catalyst with remarkable mass activity of 3.25 mA μg−1 for alkaline hydrogen oxidation reaction (HOR), which is 8‐fold enhancement compared to that of commercial Pt/C. Through machine learning potential‐based Monte Carlo simulation, we reveal that the dominant Pd−Pd−Ni/Pd−Pd−Pd bonding environments and Ni/Ru oxophilic sites on HEA surface are beneficial to the optimized adsorption/desorption of *H and enhanced *OH adsorption, contributing to the excellent HOR activity and stability. This work provides significant insights into atomic structure and catalytic mechanism for HEA and offers novel prospects for developing advanced HOR electrocatalysts.