Hydrogen Oxidation Reaction Catalyst Research Articles

Unraveling Stoichiometry Effect in Nickel‐Tungsten Alloys for Efficient Hydrogen Oxidation Catalysis in Alkaline Electrolytes

AbstractAnion‐exchange membrane fuel cells provide the possibility to use platinum group metal‐free catalysts, but the anodic hydrogen oxidation reaction (HOR) suffers from sluggish kinetics and its source is still debated. Here, over nickel‐tungsten (Ni−W) alloy catalysts, we show that the Ni : W ratio greatly governs the HOR performance in alkaline electrolyte. Experimental and theoretical studies unravel that alloying with W can tune the unpaired electrons in Ni, tailoring the potential of zero charge and the catalytic surface to favor hydroxyl adsorption (OHad). The OHad species coordinately interact with potassium (K+) ions, which break the K+ solvation sheath to leave free water molecules, yielding an improved connectivity of hydrogen‐bond networks. Consequently, the optimal Ni17W3 alloy exhibits alkaline HOR activity superior to the state‐of‐the‐art platinum on carbon (Pt/C) catalyst and operates steadily with negligible decay after 10,000 cycles. Our findings offer new understandings of alloyed HOR catalysts and will guide rational design of next‐generation catalysts for fuel cells.

Unraveling Stoichiometry Effect in Nickel-Tungsten Alloys for Efficient Hydrogen Oxidation Catalysis in Alkaline Electrolytes.

Anion-exchange membrane fuel cells provide the possibility to use platinum group metal-free catalysts, but the anodic hydrogen oxidation reaction (HOR) suffers from sluggish kinetics and its source is still debated. Here, over nickel-tungsten (Ni-W) alloy catalysts, we show that the Ni : W ratio greatly governs the HOR performance in alkaline electrolyte. Experimental and theoretical studies unravel that alloying with W can tune the unpaired electrons in Ni, tailoring the potential of zero charge and the catalytic surface to favor hydroxyl adsorption (OHad). The OHad species coordinately interact with potassium (K+) ions, which break the K+ solvation sheath to leave free water molecules, yielding an improved connectivity of hydrogen-bond networks. Consequently, the optimal Ni17W3 alloy exhibits alkaline HOR activity superior to the state-of-the-art platinum on carbon (Pt/C) catalyst and operates steadily with negligible decay after 10,000 cycles. Our findings offer new understandings of alloyed HOR catalysts and will guide rational design of next-generation catalysts for fuel cells.

Local Charge Transfer Unveils Antideactivation of Ru at High Potentials for the Alkaline Hydrogen Oxidation Reaction.

The activity of Ru-based alkaline hydrogen oxidation reaction (HOR) electrocatalysts usually decreases rapidly at potentials higher than 0.1 V (vs a reversible hydrogen electrode (RHE)), which significantly limits the lifetime of fuel cells. It is found that this phenomenon is caused by the overadsorption of the O species due to the overcharging of Ru nanoparticles at high potentials. Here, Mn1Ox(OH)y clusters-modified Ru nanoparticles (Mn1Ox(OH)y@Ru/C) were prepared to promote charge transfer from overcharged Ru nanoparticles to Mn1Ox(OH)y clusters. Mn1Ox(OH)y@Ru/C exhibits high HOR activity and stability over a wide potential range of 0-1.0 V. Moreover, a hydroxide exchange membrane fuel cell with a Mn1Ox(OH)y@Ru/C anode delivers a high peak power density of 1.731 W cm-2, much superior to that of a Pt/C anode. In situ X-ray absorption fine structure (XAFS) analysis and density functional theory (DFT) calculations reveal that Mn in Mn1Ox(OH)y clusters could receive more electrons from overcharged Ru at higher potentials and significantly decrease the overadsorption of the O species on Ru, thus permitting the HOR on Ru to proceed at high potentials. This study provides guidance for the design of alkaline HOR catalysts without activity decay at high potentials.

Atomically dispersed Iridium on Mo2C as an efficient and stable alkaline hydrogen oxidation reaction catalyst

Hydroxide exchange membrane fuel cells (HEMFCs) have the advantages of using cost-effective materials, but hindered by the sluggish anodic hydrogen oxidation reaction (HOR) kinetics. Here, we report an atomically dispersed Ir on Mo2C nanoparticles supported on carbon (IrSA-Mo2C/C) as highly active and stable HOR catalysts. The specific exchange current density of IrSA-Mo2C/C is 4.1 mA cm−2ECSA, which is 10 times that of Ir/C. Negligible decay is observed after 30,000-cycle accelerated stability test. Theoretical calculations suggest the high HOR activity is attributed to the unique Mo2C substrate, which makes the Ir sites with optimized H binding and also provides enhanced OH binding sites. By using a low loading (0.05 mgIr cm−2) of IrSA-Mo2C/C as anode, the fabricated HEMFC can deliver a high peak power density of 1.64 W cm−2. This work illustrates that atomically dispersed precious metal on carbides may be a promising strategy for high performance HEMFCs.

Balancing the Binding of Intermediates Enhances Alkaline Hydrogen Oxidation on D-Band Center Modulated Pd Sites.

Exploring efficient alkaline hydrogen oxidation reaction (HOR) electrocatalysts is of great concern for constructing anion exchange membrane fuel cells (AEMFCs). Herein, d-band center modulated PdCo alloys with ultralow Pd content anchored onto the defective carbon support (abbreviated as PdCo/NC hereafter) are proposed as highly efficient HOR catalyst. The as-prepared catalyst exhibits exceptional HOR performance compared to the Pt/C catalyst, achieving thermodynamically spontaneous and kinetically preferential reactions. Specifically, the resultant PdCo/NC demonstrates a marked enhancement in alkaline HOR performance, with the highest mass and specific activities of 1919.6 mA mgPd-1 and 1.9 mA cm-2, 51.1 and 4.2 times higher than those of benchmark of Pt/C, along with an excellent stability in a chronoamperometry test. In the analysis of in situ Raman spectra, it was discovered that tetrahedrally coordinated H-bonded water molecules were formed during the HOR process. This indicates that the promotion of interfacial water molecule formation and enhancement of HOR activities in PdCo/NC are facilitated by defect engineering and the turning of d-band center in PdCo alloy. The essential knowledge obtained in this study could open up a new direction for modifying the electronic structure of cost-effective HOR catalysts through electronic structure engineering.

Advanced Ru/Ti4O7 catalyst for Tolerating CO and H2S poisoning to hydrogen oxidation reaction

CO and H2S poisoning of Pt-based catalysts for hydrogen oxidation reaction (HOR) stands as one of the long-standing hindrances to the widespread commercialization of proton exchange membrane fuel cells. In this paper, a Ru/Ti4O7 catalyst is successfully synthesized by the microwave-thermal method. This Ru/Ti4O7 catalyst shows a much higher noble metal mass activity than those of commercial PtRu/C and conventional Ru/C catalysts. The performance of the Ru/Ti4O7 catalyst under the exist of CO or H2S shows insignificant current decay, which is far superior to commercial PtRu/C and Pt/C catalysts. In this Ru/Ti4O7 catalyst, the electron transfer between Ru and Ti to form d-p orbital hybridization is considered to be responsible for the favorable catalytic HOR performance and the corresponding CO and H2S tolerance. The interaction mechanism formed by electron transfer may open a promising way for the subsequent development of anti-poisoning catalysts for PEM fuel cell hydrogen oxidation reaction.

CO-Tolerant Hydrogen Oxidation Electrocatalysts for Low-Temperature Hydrogen Fuel Cells.

The severe performance degradation of low-temperature hydrogen fuel cells upon exposure to trace amounts of carbon monoxide (CO) impurities in reformate hydrogen fuels is one of the challenges that hinders their commercialization. Despite significant efforts that have been made, the CO-tolerance performance of electrocatalysts for the hydrogen oxidation reaction (HOR) is still unsatisfactory. This Perspective discusses the path forward for the rational design of CO-tolerant HOR electrocatalysts. The fundamentals of the CO-tolerant mechanisms on commercialized platinum group metal (PGM) electrocatalysts via either promoting CO electrooxidation or weakening CO adsorption are provided, and comprehensive discussions based on these strategies are presented with typical examples. Given the recent progress, some emerging strategies, including blocking CO diffusion with a barrier layer and developing non-PGM HOR catalysts, are also discussed. We conclude with a discussion of the strengths and limitations of these strategies along with the perspectives of the major challenges and opportunities for future research on CO-tolerant HOR electrocatalysts.

Unveiling the nature of Pt-induced anti-deactivation of Ru for alkaline hydrogen oxidation reaction

While Ru owns superior catalytic activity toward hydrogen oxidation reaction and cost advantages, the catalyst deactivation under high anodic potential range severely limits its potential to replace the Pt benchmark catalyst. Unveiling the deactivation mechanism of Ru and correspondingly developing protection strategies remain a great challenge. Herein, we develop atomic Pt-functioned Ru nanoparticles with excellent anti-deactivation feature and meanwhile employ advanced operando characterization tools to probe the underlying roles of Pt in the anti-deactivation. Our studies reveal the introduced Pt single atoms effectively prevent Ru from oxidative passivation and consequently preserve the interfacial water network for the critical H* oxidative release during catalysis. Clearly understanding the deactivation nature of Ru and Pt-induced anti-deactivation under atomic levels could provide valuable insights for rationally designing stable Ru-based catalysts for hydrogen oxidation reaction and beyond.

Tuning the apparent hydrogen binding energy to achieve high-performance Ni-based hydrogen oxidation reaction catalyst

High-performance platinum-group-metal-free alkaline hydrogen oxidation reaction catalysts are essential for the hydroxide exchange membrane fuel cells, which generally require high Pt loadings on the anode. Herein, we report a highly active hydrogen oxidation reaction catalyst, NiCuCr, indicated by the hydroxide exchange membrane fuel cell with a high peak power density of 577 mW cm−2 (18 times as high as the Ni/C anode) and a stability of more than 150 h (a degradation rate slower by 7 times than the Ni/C anode). The spectroscopies demonstrate that the alloy effect from Cu weakens the hydrogen binding, and the surface Cr2O3 species enhance the interfacial water binding. Both effects bring an optimized apparent hydrogen binding energy and thus lead to the high hydrogen oxidation reaction performance of NiCuCr. These results suggest that the apparent hydrogen binding energy determines the hydrogen oxidation reaction performance and that its tuning is beneficial toward high electrocatalytic performance.

Nickel-molybdenum hydrogen evolution and oxidation reaction electrocatalyst obtained by electrospinning

To accelerate the deployment of anion exchange membrane (AEM) technologies, and break free from our reliance on expensive and rare platinum group metals (PGM), this study explores a novel family of non-PGM electrocatalysts capable of both hydrogen evolution and oxidation. By thermal reduction, nanoparticles of nickel-molybdenum, 9:1 atomic ratio, were grown on fibrous carbon supports obtained by electrospinning and doped with carbon nanotubes (CNT). Complimentary characterization techniques confirm the integration of the CNT with the carbon fibers and a high loading of active alloy material on the support. In particular, XANES indicates a strong interaction between NiMo and the CNT. When supported on undoped carbon fibers, NiMo shows superior activity towards the hydrogen oxidation reaction (HOR) compared to the doped carbon supports. However, heat treating the catalysts in 10 % NH3/ 90 % N2 upsets this trend, while also improving the HOR performance of all the catalysts based on several performance indicators. In the case of NiMo on carbon fibers containing 7 wt% CNT, denoted as NiMo/CF(7 %), the ammonia heat treatment produced a five-fold increase in the kinetic current. The catalysts NiMo/CF(7 %)-NH3 and NiMo/CF(24 %)-NH3, also capable of hydrogen evolution, match other state-of-the-art PGM-free HOR catalysts for their remarkable specific activity.

Optimizing Nickel Orbital Occupancy via Co‐Modulation of Core and Shell Structures to Accelerate Alkaline Hydrogen Electro‐Oxidation Reaction

AbstractNickel‐based catalysts are recognized as a promising alternative to platinum‐based catalysts for the alkaline hydrogen oxidation reaction (HOR) yet suffer from poor stability and relatively low activity. Herein, a nitrogen ligand‐assisted approach is reported to encapsulate nickel‐copper nanoparticles within few carbon layers, and by modulating the core and shell components/structure, the charge distribution in the nanostructures can be finely regulated. The optimized Ni93Cu7@NC catalyst exhibits outstanding HOR activity with an intrinsic activity of 61.0 µA cm−2 and excellent stability, which is among the most advanced Ni‐based HOR catalysts. Notably, an alkaline exchange membrane fuel cell utilizing this catalyst achieves a peak power density of 381 mW cm−2 and maintains stability at 100 mA cm−2 for over 24 h. Experimental and theoretical investigations unveil that the electron re‐distribution at the interface of NiCu core and nitrogen‐doped carbon reduces the electron occupancy in Ni 4s‐H 1s bonding orbitals and Ni 3dz2/yz‐O 2p antibonding orbitals, leading to a weakened hydrogen binding energy and enhance hydroxide binding energy. Consequently, the limiting energy for the HOR is reduced following a bifunctional mechanism on the Ni93Cu7@NC. This work provides a core‐shell co‐modulation strategy to accurately regulate the electronic structure of transition metals to design robust catalysts.

Amorphous-crystalline RuTi nanosheets enhancing OH species adsorption for efficient hydrogen oxidation catalysis.

Anion exchange membrane fuel cells are a potentially cost-effective energy conversion technology, however, the electrocatalyst for the anodic hydrogen oxidation reaction (HOR) suffers from sluggish kinetics under alkaline conditions. Herein, we report that Ru-based nanosheets with amorphous-crystalline heterointerfaces of Ru and Ti-doped RuO2 (a/c-Ru/Ti-RuO2) can serve as a highly efficient HOR catalyst with a mass activity of 4.16 A mgRu-1, which is 19.8-fold higher than that of commercial Pt/C. Detailed characterization studies show that abundant amorphous-crystalline heterointerfaces of a/c-Ru/Ti-RuO2 nanosheets provide oxygen vacancies and unsaturated coordination bonds for balancing adsorption of hydrogen and hydroxyl species on Ru active sites to elevate HOR activity. Moreover, Ti doping can facilitate CO oxidation, leading to enhanced strength to CO poisoning. This work provides a strategy for enhancing alkaline HOR performance over Ru-based catalysts with heteroatom and heterointerface dual-engineering, which will attract immediate interest in chemistry, materials science and beyond.

Highly Dispersed Pt on Ceria with N-Doped Carbon As High Durable Catalyst for ORR and High Tolerant to H2s and CO for HOR in PEMFCs

Proton Exchange Membrane Fuel Cells (PEMFCs) are one of the most promising clean and efficient energy conversion devices. However, carbon supported Pt-based electrocatalysts, widely used in PEMFCs, show poor stability due to the carbon oxidation and unstable Pt in practical application. Hydrogen starvation at anode and unprotected startup/shutdown of PEMFCs can arouse high potential over 1.3V resulting in severe carbon corrosion and irreversible performance loss. With increased electron conductivity, the doped metal oxides Ti3O5Mo0.2Si0.4 (TOMS) [1], Nb-TiO2 [ 2], Ta0.3Ti0.7O2 [ 3], Sb-SnO2 [ 4], W-SnOx and TiOx [ 5] show great potential as durable catalyst supports that can stand over 1.0V for PEMFCs. Furthermore, strong metal support interactions (SMSI) of Pt and the support also enhance the stability of Pt.CeO2 which exhibits good dynamic oxygen storage and release capacity, strong redox capacity, was deposited on N-doped carbon (NC) as support. Pt was highly dispersed on the CeO2/NC to form Pt/CeO2/NC catalyst. Accelerated degradation test (ADT) was carried out by sweeping voltage from 1.0V to 1.2V on a GC disk with a Pt loading of 20 μgPt·cm-2 in the oxygen saturated 0.1M HClO4 electrolyte with a scan rate of 10mV·s-1, while the Pt ring was held at 1.2V vs. RHE. Fig 1 shows the morphology of as-prepared CeO2/NC and Pt/CeO2/NC, the LSV and CV of Pt/CeO2/NC after different cycles of ADT. The specific mass activity at 0.9ViR free (im@0.9V) for oxygen reduction reaction (ORR) of Pt/CeO2/NC was 105mA×mg-1 and slightly increased about 8% after 10000 cycles.On the other hand, precious metal on CeO2 is high efficient CO oxidation catalyst [6-7] and widely applied for H2 purification from reformate gases. CeO2 was applied as H2S oxidant [8] too. This broadens the Pt/CeO2/NC as a high H2S and CO tolerant catalyst for hydrogen oxidation reaction (HOR). The high dispersion of Pt nano particle, the interaction between the poison gases and Pt and/or CeO2 was believed to contribute. The theoretical and experimental details will be presented at the symposium.Reference A. M. Esfahani, E. B. Easton. Applied Catalysis B: Environmental, 2020, 268, 118743.H. Cheng, Sankarasubramanian, I. Matanovic, P. Atanassov, V. Ramani. ChemSusChem, 2019, 12, 3468. Kumar, V. Ramani. ACS Catal. 2014, 4, 1516.Ozouf, G. Cognard,F. Maillard, M. Chatenet, L. Gu´etaz,M. Heitzmann, P. A. Jacques, C. Beauger. J. Electrochem. Soc., 2019, 165(6), F3036.T. Arai, O. Takashi, K. Amemiya, T. Takahashi. SAE Int. J. Alt. Power. 2017, 6 (1), 145.Y. Kardash1, E. A. Derevyannikova, E. M. Slavinskaya, A. I. Stadnichenko, V. A. Maltsev, A. V. Zaikovskii, S. A. Novopashin, A. I. Boronin1, K. M. Neyman. Frontiers in Chemistry, 2019, 7, 114. Maurer, J. Jelic, J. Wang, A. Gänzler, P. Dolcet, C. Wöll, Y. Wang, F. Studt, M. Casapu, J. Grunwaldt. Nature Catalysis, 2020, 3, 824.X. Zheng, Y. Li, L. Zhang, L. Shen, Y. Xiao, Y. Zhang,C. Au, L. Jiang. Applied Catalysis B: Environmental, 2019, 252, 98. Figure 1

Engineering Ru–RuO2 interface with regulated hydroxyl adsorption towards efficient and CO-tolerant hydrogen oxidation reaction

Owning to the similar hydrogen binding strength and lower price, Ru is considered as a promising substitute for Pt towards hydrogen oxidation reaction (HOR). However, the unoptimized intermediate adsorption on metallic Ru site makes Ru/C inferior to Pt/C benchmark in terms of lower HOR activity as well as CO tolerance. Herein, we developed a novel competitive adsorption strategy through the construction of Ru–RuO2 interface to enhance alkaline HOR performance and CO tolerance simultaneously. Specifically, the competitive adsorption of OH* between Ru and RuO2 could alleviate the strong affinity of OH* on Ru, which would promote both alkaline HOR and CO oxidation significantly. Besides, the engineered interface structure optimized hydrogen binding energy (HBE) via electronic modulation effect as well. Benefitting from these attributes, the as-designed Ru–RuO2/C catalyst exhibits remarkable HOR performance with a mass activity of 2.50 A mg−1 @ 50 mV, which is 10 and 5 times higher than that of Ru/C and commercial Pt/C, respectively. More strikingly, Ru–RuO2/C performs unprecedented anti-poisoning capacity towards CO, with only a small decrease of 6.9 % in the limiting current density in the presence of 30,000 ppm CO, far surpassing the commercial Pt/C catalyst. This work not only provides a cost-effective and robust HOR catalyst in alkaline media, but also opens up a new avenue to tailor the adsorption-desorption properties of intermediates on heterogenous electrocatalyst.

High-Stability RuNi/C Electrocatalyst for Efficient Hydrogen Oxidation Reaction in Alkaline Condition.

The Ru-based catalyst for hydrogen oxidation reaction (HOR) with remarkable activity and reliability at high potential range remains a formidable challenge. Herein, the RuNi/C nanoparticles are customized, in which NiRu alloy is tightly wrapped with a carbon layer, delivering 2.2-fold and 8.3-fold enhancement in kinetic current density than that of commercial Pt/C and Ru/C, respectively. Notably, the current density maintains 2.93mAcm-2 disk at 0.6 V vsRHE, which effectively improves the stability of Ru-based catalysts at high voltage. The NiRu alloy triggers electron redistribution between two metal elements and regulates the surface adsorption performance, coupled with a tightly wrapped outer carbon layer which is in situ formed with alloy as a good conductor of electronic and protection from the electrolyte. This work not only provides a novel electrocatalyst for efficient HOR with its potential for industrial application but also opens up a new avenue for designing highly active catalytic systems.

Boosting Alkaline Hydrogen Oxidation Activity of Ru Single-Atom Through Promoting Hydroxyl Adsorption on Ru/WC1- x Interfaces.

The sluggish kinetics of the hydrogen oxidation reaction (HOR) in alkaline conditions continue to pose a significant challenge for the practical implementation of anion-exchange membrane fuel cells. Developing single-atom catalysts can accelerate the pace of new HOR catalyst discovery for highly cost-effective and active HOR performance. However, single-atom catalysts (SACs) for the alkaline HOR have rarely been reported, and fundamental studies on the rational design of SACs are still required. Herein, the design of Ru SAC supported on the tungsten carbide (Ru SA/WC1- x ) via in situ high-temperature annealing strategy is reported. The resulting Ru SA/WC1- x catalyst exhibits remarkably enhanced HOR performance in alkaline media, a level of activity that can not be achieved with carbon-supported Ru SAC. Electrochemical results and density functional theory demonstrate that promoting the hydroxyl adsorption on Ru SA/WC1- x interfaces, which is derived from the low potential of zero charge of WC1- x support, has a significant effect on enhancing the HOR performance of SACs. This enhancement leads to 5.8 and 60.1 times higher Ru mass activity of Ru SA/WC1- x than Ru nanoparticles on carbon and Ru single-atom on N-doped carbon, respectively. This work provides new insights into the design of highly active SACs for alkaline HOR.

Hydrogen oxidation reaction catalysts derived from Co, Ni-coordination compounds and polymers (MOFs)

Aiming to obtain catalysts for the Hydrogen Oxidation Reaction (HOR) and to construct fuel cells completely free of noble metals, two Ni-MOFs, a Ni-coordination polymer, and a Ni-complex were synthesized, together with their corresponding Co and NiCo analogs. The following N-heterocyclic ligands were employed: 2-Methylimidazolate, imidazolate, nicotinate, 2,3-pyrazinedicarboxylate and pyrazinecarboxylate. These precursor compounds were pyrolyzed at 700 °C obtaining metallic nanoparticles embedded within N-doped mesoporous carbons. These materials were characterized by different physical and electrochemical techniques. The catalysts exhibited HOR activities (jη = 50 mv) comparable to the best-reported materials, i.e.: 1.3 and 0.6 mA cm−2disk for the Ni imidazolate and Ni nicotinate derived materials respectively. The results are relevant for the design of new catalysts and to construct alkaline anion exchange membrane fuel cells completely free of platinum group metals.

Co2P-Fe2P heterogeneous nanoparticles: Efficient hydrogen oxidation/evolution electrocatalysts and surface reconstruction in alkaline media

Hydrogen evolution and oxidation are critical to realizing hydrogen energy recycling and to the hydrogen economy. Therefore, it is important to develop non-precious metal catalysts with high efficiency and stability for the hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR). In this study, we reported on the facile synthesis of Co2P-Fe2P heterogeneous nanoparticles on a porous carbon skeleton (Co2P-Fe2P/C), which exhibited high activity for both HOR and HER in alkaline conditions. The overpotential of Co2P-Fe2P/C toward HER was 77 mV at 10 mA cm−2, with a Tafel slope of 42 mV dec−1 and excellent stability under long-term testing after 120 h. The current density at 0.1 V for HOR was 1.68 mA cm−2, which was close to that of commercial Pt/C. In situ Raman spectroscopy indicated that surface reconstruction was involved for Co2P-Fe2P/C, CoFe2O4, and FeOOH, as detected during HOR. Density functional theory calculations revealed strong electron interaction between Fe2P and Co2P at the heterogeneous interfaces, resulting in an optimal hydrogen adsorption strength for HER. This study significantly contributes to the realization of low-cost and high-efficiency bifunctional catalysts for HER and HOR.

Recent Advances in Platinum Group Metal Based Alloys for Alkaline Hydrogen Oxidation Reaction

AbstractThe development of efficient electrocatalysts for alkaline hydrogen oxidation reaction (HOR) is crucial to realize the commercialized application of alkaline exchange membrane fuel cells. Platinum group metals (PGMs) have been extensively used as alkaline HOR catalysts because they exhibit high activity and stability. Currently, searching for methods to improve the catalytic activity and reduce the loading of PGMs is the main research interest of PGM‐based electrocatalysts. The alloying method has been regarded as an effective strategy. In this review, we summarized various kinds of PGM‐based alloys, including traditional random alloys, single‐atom alloys, high‐entropy alloys and intermetallic compounds, and highlighted the challenges and future directions regarding the development of advanced PGM‐based alloys.

Directional electronic tuning of Ni nanoparticles by interfacial oxygen bridging of support for catalyzing alkaline hydrogen oxidation.

Metallic nickel (Ni) is a promising candidate to substitute Pt-based catalysts for hydrogen oxidation reaction (HOR), but huge challenges still exist in precise modulation of the electronic structure to boost the electrocatalytic performances. Herein, we present the use of single-layer Ti3C2Tx MXene to deliberately tailor the electronic structure of Ni nanoparticles via interfacial oxygen bridges, which affords Ni/Ti3C2Tx electrocatalyst with exceptional performances for HOR in an alkaline medium. Remarkably, it shows a high kinetic current of 16.39 mA cmdisk-2 at the overpotential of 50 mV for HOR [78 and 2.7 times higher than that of metallic Ni and Pt/C (20%), respectively], also with good durability and CO antipoisoning ability (1,000 ppm) that are not available for conventional Pt/C (20%) catalyst. The ultrahigh conductivity of single-layer Ti3C2Tx provides fast transmission of electrons for Ni nanoparticles, of which the uniform and small sizes endow them with high-density active sites. Further, the terminated -O/-OH functional groups on Ti3C2Tx directionally capture electrons from Ni nanoparticles via interfacial Ni-O bridges, leading to obvious electronic polarization. This could enhance the Nids-O2p interaction and weaken Nids-H1s interaction of Ni sites in Ni/Ti3C2Txenabling a suitable H-/OH-binding energy and thus enhancing the HOR activity.