Kinetics Of Hydrogen Oxidation Reaction Research Articles

Revealing interfacial charge redistribution of homologous Ru-RuS2 heterostructure toward robust hydrogen oxidation reaction

Precisely tailoring the surface electronic structures of electrocatalysts for optimal hydrogen binding energy and hydroxide binding energy is vital to improve the sluggish kinetics of hydrogen oxidation reaction (HOR). Herein, we employ a partial desulfurization strategy to construct a homologous Ru-RuS2 heterostructure anchored on hollow mesoporous carbon nanospheres (Ru-RuS2@C). The disparate work functions of the heterostructure contribute to the spontaneous formation of a unique built-in electric field, accelerating charge transfer and boosting conductivity of electrocatalyst. Consequently, Ru-RuS2@C exhibits robust HOR electrocatalytic activity, achieving an exchange current density and mass activity as high as 3.56 mA cm−2 and 2.13 mA μgRu-1, respectively, exceeding those of state-of-the-art Pt/C and most contemporary Ru-based HOR electrocatalysts. Surprisingly, Ru-RuS2@C can tolerate 1000 ppm of CO that lacks in Pt/C. Comprehensive analysis reveals that the directional electron transfer across Ru-RuS2 heterointerface induces local charge redistribution in interfacial region, which optimizes and balances the adsorption energies of H and OH species, as well as lowers the energy barrier for water formation, thereby promoting the HOR performance.

High‐Performance Anion Exchange Membrane Fuel Cells Enabled by Nitrogen Configuration Optimization in Graphene‐Coated Nickel for Enhanced Hydrogen Oxidation

Anion exchange membrane fuel cell (AEMFC) technology is attracting intensive attention, due to its great potential by using non‐precious‐metal catalysts (NPMCs) in the cathode and cheap bipolar plate materials in alkaline media. However, in such case, the kinetics of hydrogen oxidation reaction (HOR) in the anode is two orders of magnitude sluggish than that of acidic electrolytes, which is recognized as the grand challenge in this field. Herein, we report the rationally designed Ni nanoparticles encapsulated by N‐doped graphene layers (Ni@NG) using a facile pyrolysis strategy. Based on the density functional theory calculations and electrochemical performance analysis, it is witnessed that the rich Pyridinic‐N within the graphene shell optimizes the binding energy of the intermediates, thus enabling the fundamentally enhanced activity for HOR with robust stability. As a proof of concept, the resultant Ni@NG sample as the anode with a low loading (1.8 mg cm−2) in AEMFCs delivers a high peak power density of 500 mW cm−2, outperforming all of those of NPMC‐based analogs ever reported.

Symmetry-Broken Ru Nanoparticles with Parasitic Ru-Co Dual-Single Atoms Overcome the Volmer Step of Alkaline Hydrogen Oxidation.

Efficient dual-single-atom catalysts are crucial for enhancing atomic efficiency and promoting the commercialization of fuel cells, but addressing the sluggish kinetics of hydrogen oxidation reaction (HOR) in alkaline media and the facile dual-single-atom site generation remains formidable challenges. Here, we break the local symmetry of ultra-small ruthenium (Ru) nanoparticles by embedding cobalt (Co) single atoms, which results in the release of Ru single atoms from Ru nanoparticles on reduced graphene oxide (Co1 Ru1,n /rGO). In situ operando spectroscopy and theoretical calculations reveal that the oxygen-affine Co atom disrupts the symmetry of ultra-small Ru nanoparticles, resulting in parasitic Ru and Co dual-single-atom within Ru nanoparticles. The interaction between Ru single atoms and nanoparticles forms effective active centers. The parasitism of Co atoms modulates the adsorption of OH intermediates on Ru active sites, accelerating HOR kinetics through faster formation of *H2 O. As anticipated, Co1 Ru1,n /rGO exhibits ultrahigh mass activity (7.68 A mgRu -1 ) at 50 mV and exchange current density (0.68 mA cm-2 ), which are 6 and 7 times higher than those of Ru/rGO, respectively. Notably, it also displays exceptional durability surpassing that of commercial Pt catalysts. This investigation provides valuable insights into hybrid multi-single-atom and metal nanoparticle catalysis.

Symmetry‐Broken Ru Nanoparticles with Parasitic Ru‐Co Dual‐Single Atoms Overcome the Volmer Step of Alkaline Hydrogen Oxidation

AbstractEfficient dual‐single‐atom catalysts are crucial for enhancing atomic efficiency and promoting the commercialization of fuel cells, but addressing the sluggish kinetics of hydrogen oxidation reaction (HOR) in alkaline media and the facile dual‐single‐atom site generation remains formidable challenges. Here, we break the local symmetry of ultra‐small ruthenium (Ru) nanoparticles by embedding cobalt (Co) single atoms, which results in the release of Ru single atoms from Ru nanoparticles on reduced graphene oxide (Co1Ru1,n/rGO). In situ operando spectroscopy and theoretical calculations reveal that the oxygen‐affine Co atom disrupts the symmetry of ultra‐small Ru nanoparticles, resulting in parasitic Ru and Co dual‐single‐atom within Ru nanoparticles. The interaction between Ru single atoms and nanoparticles forms effective active centers. The parasitism of Co atoms modulates the adsorption of OH intermediates on Ru active sites, accelerating HOR kinetics through faster formation of *H2O. As anticipated, Co1Ru1,n/rGO exhibits ultrahigh mass activity (7.68 A mgRu−1) at 50 mV and exchange current density (0.68 mA cm−2), which are 6 and 7 times higher than those of Ru/rGO, respectively. Notably, it also displays exceptional durability surpassing that of commercial Pt catalysts. This investigation provides valuable insights into hybrid multi‐single‐atom and metal nanoparticle catalysis.

Improving Alkaline Hydrogen Oxidation through Dynamic Lattice Hydrogen Migration in Pd@Pt Core-Shell Electrocatalysts.

Tracking the trajectory of hydrogen intermediates during hydrogen electro-catalysis is beneficial for designing synergetic multi-component catalysts with division of chemical labor. Herein, we demonstrate a novel dynamic lattice hydrogen (LH) migration mechanism that leads to two orders of magnitude increase in the alkaline hydrogen oxidation reaction (HOR) activity on Pd@Pt over pure Pd, even ≈31.8 times mass activity enhancement than commercial Pt. Specifically, the polarization-driven electrochemical hydrogenation process from Pd@Pt to PdHx @Pt by incorporating LH allows more surface vacancy Pt sites to increase the surface H coverage. The inverse dehydrogenation process makes PdHx as an H reservoir, providing LH migrates to the surface of Pt and participates in the HOR. Meanwhile, the formation of PdHx induces electronic effect, lowering the energy barrier of rate-determining Volmer step, thus resulting in the HOR kinetics on Pd@Pt being proportional to the LH concentration in the in situ formed PdHx @Pt. Moreover, this dynamic catalysis mechanism would open up the catalysts scope for hydrogen electro-catalysis.

Improving Alkaline Hydrogen Oxidation through Dynamic Lattice Hydrogen Migration in Pd@Pt Core‐Shell Electrocatalysts

AbstractTracking the trajectory of hydrogen intermediates during hydrogen electro‐catalysis is beneficial for designing synergetic multi‐component catalysts with division of chemical labor. Herein, we demonstrate a novel dynamic lattice hydrogen (LH) migration mechanism that leads to two orders of magnitude increase in the alkaline hydrogen oxidation reaction (HOR) activity on Pd@Pt over pure Pd, even ≈31.8 times mass activity enhancement than commercial Pt. Specifically, the polarization‐driven electrochemical hydrogenation process from Pd@Pt to PdHx@Pt by incorporating LH allows more surface vacancy Pt sites to increase the surface H coverage. The inverse dehydrogenation process makes PdHx as an H reservoir, providing LH migrates to the surface of Pt and participates in the HOR. Meanwhile, the formation of PdHx induces electronic effect, lowering the energy barrier of rate‐determining Volmer step, thus resulting in the HOR kinetics on Pd@Pt being proportional to the LH concentration in the in situ formed PdHx@Pt. Moreover, this dynamic catalysis mechanism would open up the catalysts scope for hydrogen electro‐catalysis.

A Highly-Efficient Boron Interstitially Inserted Ru Anode Catalyst for Anion Exchange Membrane Fuel Cells.

Developing high-performance electrocatalysts for alkaline hydrogen oxidation reaction (HOR) is crucial for the commercialization of anion exchange membrane fuel cells (AEMFCs). Here, boron interstitially inserted ruthenium (B-Ru/C) is synthesized and used as an anode catalyst for AEMFC, achieving a peak power density of 1.37W cm-2 , close to the state-of-the-art commercial PtRu catalyst. Unexpectedly, instead of the monotonous decline of HOR kinetics with pH as generally believed, an inflection point behavior in the pH-dependent HOR kinetics on B-Ru/C is observed, showing an anomalous behavior that the HOR activity under alkaline electrolyte surpasses acidic electrolyte. Experimental results and density functional theory calculations reveal that the upshifted d-band center of Ru after the intervention of interstitial boron can lead to enhanced adsorption ability of OH and H2 O, which together with the reduced energy barrier of water formation, contributes to the outstanding alkaline HOR performance with a mass activity of 1.716mA µgPGM -1 , which is 13.4-fold and 5.2-fold higher than that of Ru/C and commercial Pt/C, respectively.

Electrochemical properties of mechanically milled Ni-20Cr for H2 oxidation in alkaline fuel cells

The electrochemical properties of Ni-20Cr alloy subject to high-energy mechanical milling were investigated to analyze its potential as a catalyst in fuel cells for hydrogen oxidation reaction (HOR) in an alkaline medium. The kinetic properties of Ni-20Cr alloy decorated with Pt are also reported. Results showed that as the milling time increases, the HOR kinetics improve. Pt particles grow mainly on the surface of highly deformed Ni-20Cr particles. Ni-20Cr and Ni-20Cr/Pt with 12 and 8 h of milling, respectively, are good candidates for HOR in an alkaline medium.

A Highly Efficient pH‐Universal HOR Catalyst with Engineered Electronic Structures of Single Pt Sites by Isolated Co Atoms

AbstractDeveloping a high‐efficiency, stable, and CO‐toxicant‐resistant low‐cost hydrogen oxidation reaction (HOR) electrocatalyst is challenging but is vital for practical proton/anion exchange membrane fuel cells. Herein, an efficient pH‐universal HOR catalyst Pt1@Co1CN is fabricated, in which the electronic structure of single Pt sites is modulated by isolated Co atoms pre‐anchored on nitrogen‐doped carbon. Pt1@Co1CN exhibits superior HOR activity and durability under pH‐universal media than Pt1@CN (anchored single Pt atoms on nitrogen‐doped carbon) and commercial PtRu/C and Pt/C. More importantly, Pt1@Co1CN possesses much better CO anti‐poisoning ability than Pt1@CN and commercial PtRu/C and Pt/C. It is speculated that the superior pH‐universal HOR performance can be attributed to the inter‐regulation of adjacent Co and Pt sites, leading to the downshift of anti‐bonding state and consequently strengthening the *H adsorption, which promotes the kinetics of HOR.

Modifying charge transfer between rhodium and ceria for boosted hydrogen oxidation reaction in alkaline electrolyte

Sluggish kinetics of hydrogen oxidation reaction (HOR) in alkaline solution has restricted the rapid development of hydrogen economy. Constructing catalyst with metal-oxide heterostructures can enhance HOR performance; however, little studies concentrate on charge transfer between them, and the corresponding effects on reactions remain unclear. Herein, we report charge-transfer-adjustable CeO2/Rh interfaces uniformly dispersed on multiwalled carbon nanotube (CNT), which exhibit excellent alkaline HOR performance. Results confirm that the charge transfer from Rh to CeO2 could be conveniently tuned via thermal treatment. Consequently, the adsorption free energies of H* in Rh sites and OH* adsorption strength in CeO2 could be adjusted, as corroborated by density functional theory study. The optimized CeO2/Rh interfaces exhibit an exchange current density and a mass-specific kinetic current of 0.53 mA cmPGM−2 and 830 A gPGM−1 at an overpotential of 50 mV, respectively, which surpasses most of the advanced noble-metal-based electrocatalysts. This work provides a new insight of harnessing charge transfer of heterostructure to enhance catalytic activities.

Local Oxidation Induced Amorphization of 1.5‐nm‐Thick Pt–Ru Nanowires Enables Superactive and CO‐Tolerant Hydrogen Oxidation in Alkaline Media

AbstractLow‐dimensional amorphous metallic nanomaterials provide great possibility for creating high‐performance electrocatalysts owing to their conspicuous reacting merits derived from the flexible coordination structures, but remain extremely challenging in synthesis. Herein, this work reports a facile synthesis of carbon‐loaded amorphous 1.5‐nm‐thick Pt–Ru nanowires (NWs) through a local oxidation induced amorphization process. During annealing premade crystalline Pt–Ru NWs/C in air, a local‐oxidation of the oxyphilic Ru generates abundant random Ru–O bonds and disturbs the order bimetallic lattices. The as‐prepared amorphous Pt53Ru47 (a‐Pt53Ru47) NWs/C exhibits an extremely high activity (13.7 A mg−1 at 25 mV overpotential) and an excellent CO‐tolerance for alkaline hydrogen oxidation reaction (HOR) electrocatalysis, drastically outperforming the crystalline counterpart and commercial benchmarks. Mechanism studies indicate the Pt–Ru bimetallic effects as well as the rich disordered “Pt–Ru–O” and/or “Pt–O–Ru” atomic heterojunctions can weaken the *H binding energy and inversely strengthen the *OH adsorption, thus promoting the alkaline HOR kinetics. More uniquely, the small interatomic spaces derived from the disordered bond nets present a H2/*H‐selected permeability, which spatially obstruct the relatively larger CO molecules to poison the internal catalytic sites during HOR. The CO‐shielded internal catalytic sites and the enriched surface *OH jointly upgrade the CO‐tolerance of the a‐Pt53Ru47 NWs/C catalysts.

Nickel-Based Anode Catalysts for Efficient and Affordable Anion-Exchange Membrane Fuel Cells.

ConspectusLow-temperature ion-exchange membrane hydrogen fuel cells, as zero-emission power sources, can largely preserve the merits of gasoline engines, including rapid fueling, extended cruising range, and low maintenance cost. To enable the widespread prevalence of fuel-cell automobiles, the U.S. Department of Energy (DOE) has set a long-term fuel-cell system cost target of US$30 kW-1. Over past decades, proton-exchange membrane fuel cell (PEMFC) technology has developed rapidly, resulting in the first commercial sales of fuel-cell-powered vehicles. Although there has been great success, the mass market penetration of PEMFCs is currently hindered by the excessive reliance on expensive platinum group metal (PGM) catalysts. Anion-exchange membrane fuel cells (AEMFCs), because of the alkaline environment that permits the use of PGM-free catalysts, have become an alternative technology with inherent long-term cost advantages. Thus far, significant progress has been made in the exploration of PGM-free catalysts for the oxygen reduction reaction at the AEMFC cathode, some of which have shown intrinsic catalytic properties comparable to PGM catalysts. However, the development of PGM-free catalysts for the anodic hydrogen oxidation reaction (HOR) has lagged behind, presumably owing to its sluggish kinetics in alkali. In alkaline media, the HOR kinetics is about 2 orders of magnitude slower than that in acid, which demands higher PGM loadings to reach similar fuel-cell performance in PEMFCs. Since Raney nickel (Ni) was explored for alkaline HOR catalysis in 1960s, research on Ni-based HOR catalysts has begun and now is flourishing, primarily thanks to their favorable adsorption energies of key HOR intermediates (e.g., Ni-Had and Ni-OHad). At present, a number of strategies have been developed to improve HOR performances of Ni-based materials, such as alloying, Ni nitridation, and alloy amorphization, which yield cost-effective HOR catalysts that rival or even exceed the activity and stability of PGM counterparts.In this Account, we describe our recent research endeavors toward the development of efficient Ni-based HOR catalysts for practical AEMFC anodes. First, we briefly highlight the important merits of AEMFC technology and why Ni-based materials are appealing for alkaline HOR catalysis. Critical innovations in the design of Ni-based nanostructured and bulky catalysts were then discussed, showing their great promise to catalyze alkaline HOR that traditionally relied on PGMs. To demonstrate utility, performances of the elaborately designed Ni-based catalysts under realistic fuel-cell conditions were examined, along with an initial effort to develop a CO-tolerant AEMFC anode. We conclude by outlining future research directions that allow access to next-generation PGM-free HOR catalysts for advanced AEMFCs.

Self-Optimized Ligand Effect of Single-Atom Modifier in Ternary Pt-Based Alloy for Efficient Hydrogen Oxidation

Modifying the atomic and electronic structure of platinum-based alloy to enhance its activity and anti-CO poisoning ability is a vital issue in hydrogen oxidation reaction (HOR). However, the role of foreign modifier metal and the underlying ligand effect is not fully understood. Here, we propose that the ligand effect of single-atom Cu can dynamically modulate the d-band center of Pt-based alloy for boosting HOR performance. By in situ X-ray absorption spectroscopy, our research has identified that the potential-driven structural rearrangement into high-coordination Cu-Pt/Pd intensifies the ligand effect in Pt-Cu-Pd, leading to enhanced HOR performance. Thereby, modulating the d-band structure leads to near-optimal hydrogen/hydroxyl binding energies and reduced CO adsorption energies for promoting the HOR kinetics and the CO-tolerant capability. Accordingly, PtPdCu1/C exhibits excellent CO tolerance even at 1,000 ppm impurity.

Boosting Hydrogen Oxidation Kinetics by Promoting Interfacial Water Adsorption on d-p Hybridized Ru Catalysts

The search for highly efficient and cost-effective electrocatalysts for hydrogen oxidation reaction (HOR) under alkaline electrolytes is essential for the commercial application of anion exchange membrane fuel cells. However, the kinetics of HOR in an alkaline media is much slower than that in an acidic electrolyte, which usually results in orders of magnitude decrease in the catalytic performance. Herein, we report the synthesis of d-p orbital hybridized Ru catalysts through Sn/Ga doping. Density functional theory (DFT) calculations and experimental results including H2-temperature programmed desorption (H2-TPD) and in situ Raman spectra unveil that the electronic structure modification of Ru derived from the unconventional d-p hybridization could lead to the promoted interfacial water adsorption ability and optimized hydrogen adsorption free energy during the alkaline HOR process. As expected, the d-p hybridized Ru catalyst shows much decreased formation energy of water, which contributes to the changed potential-determining step (PDS) and remarkable HOR activity with the mass activity up to 1790 mA mgRu–1. This work not only illustrates the key role of interfacial water adsorption ability but also provides a strategy for rationally designing advanced electrocatalysts for alkaline HOR.

Ru-doped WO3 enabling efficient hydrogen oxidation reaction in alkaline media.

Developing highly efficient hydrogen oxidation reaction (HOR) electrocatalysts in alkaline media is of great significance for anion exchange membrane fuel cells (AEMFCs). Herein, we report an efficient Ru-doped hexagonal tungsten trioxide (Ru-WO3) HOR electrocatalyst through a hydrothermal strategy. The prepared Ru-WO3 electrocatalyst exhibits enhanced HOR performance with a 6.1 times higher exchange current density and better durability than commercial Pt/C. Structural characterizations and theoretical calculations reveal that the uniformly distributed Ru was modulated by oxygen defects and the electron transfer from O to Ru modulated the H* adsorption of Ru sites. In addition, plenty of W sites can serve as hydroxyl adsorption sites to accelerate the HOR kinetics. This work not only provides an efficient HOR catalyst in alkaline media, but also promotes the fundamental understanding of the effect of modulation on the adsorption of H* and *OH in tungsten oxides with a relatively low oxidation state by Ru doping, broadening the range of HOR catalysts to Ru-doped metal oxides.

Steering Pt surface via N-doped carbon layer to highly active CO-tolerant hydrogen oxidation reaction catalyst in alkaline media

Improving the CO-tolerant ability of Pt-based electrocatalysts is crucial for fuel cells fed with industrial byproduct hydrogen. Herein, we present a novel core-shell structured Pt@NC/C catalyst consisting of ultrafine Pt nanoparticles (1.63 nm) as the core and ultrathin nitrogen-doped carbon layers (0.36 nm) as the shell. The catalyst exhibits excellent alkaline hydrogen oxidation reaction (HOR) activity with a mass activity of 187 A g−1Pt and a specific activity of 0.20 mA cm−2Pt, which are 1.3 and 2.2-folds to the counterpart Pt/C, respectively. More remarkably, it shows good anti CO-poisoning ability. In presence of H2 with 100 ppm CO, the HOR current degraded by 18.22% on 10% Pt/C versus only 4.81% on 10% Pt@NC/C-400. The combined X-ray photo-electron spectrum (XPS) analysis, COad stripping, CO oxidation and Zeta potential measurements imply that hydroxyl adsorption is enhanced on the NC covered Pt in 10% Pt@NC/C-400 possibly due to electron modulation induced by the strong metal and support interaction, which accelerates HOR kinetics and improvs anti-CO ability. This work provides a facile and feasible strategy to design efficient and CO-resistant Pt-based catalysts.

The Role of Discrepant Reactive Intermediates on Ru‐Ru2P Heterostructure for pH‐Universal Hydrogen Oxidation Reaction

AbstractDeveloping highly efficient electrocatalysts for hydrogen oxidation reaction (HOR) under alkaline media is essential for the commercialization of alkaline exchange membrane fuel cell (AEMFC). However, the kinetics of HOR in alkaline media is complicated, resulting in orders of magnitude slower than that in acid, even for the state‐of‐the‐art Pt/C. Here, we find that Ru‐Ru2P/C heterostructure shows HOR performance with a non‐monotonous variation in a whole pH region. Unexpectedly, an inflection point located at pH≈7 is observed, showing an anomalous behavior that HOR activity under alkaline media surpasses acidic media. Combining experimental results and theoretical calculations, we propose the roles of discrepant reactive intermediates for pH‐universal HOR, while H* and H2O* adsorption strengths are responsible for acidic HOR, and OH* adsorption strength is essential for alkaline HOR. This work not only sheds light on fundamentally understanding the mechanism of HOR but also provides new designing principles for pH‐targeted electrocatalysts.

The Role of Discrepant Reactive Intermediates on Ru-Ru2 P Heterostructure for pH-Universal Hydrogen Oxidation Reaction.

Developing highly efficient electrocatalysts for hydrogen oxidation reaction (HOR) under alkaline media is essential for the commercialization of alkaline exchange membrane fuel cell (AEMFC). However, the kinetics of HOR in alkaline media is complicated, resulting in orders of magnitude slower than that in acid, even for the state-of-the-art Pt/C. Here, we find that Ru-Ru2 P/C heterostructure shows HOR performance with a non-monotonous variation in a whole pH region. Unexpectedly, an inflection point located at pH≈7 is observed, showing an anomalous behavior that HOR activity under alkaline media surpasses acidic media. Combining experimental results and theoretical calculations, we propose the roles of discrepant reactive intermediates for pH-universal HOR, while H* and H2 O* adsorption strengths are responsible for acidic HOR, and OH* adsorption strength is essential for alkaline HOR. This work not only sheds light on fundamentally understanding the mechanism of HOR but also provides new designing principles for pH-targeted electrocatalysts.

Platinum-Water Interaction Induced Interfacial Water Orientation That Governs the pH-Dependent Hydrogen Oxidation Reaction.

Understanding the electrode-water interface structure in acid and alkali is crucial to unveiling the underlying mechanism of pH-dependent hydrogen oxidation reaction (HOR) kinetics. In this work, we construct the explicit Pt(111)-H2O interface models in both acid and alkali to investigate the relationship between the HOR mechanism and electrode-electrolyte interface structure using ab initio molecular dynamics and density functional theory. We find that the interfacial water orientation in the outer Helmholtz layer (OHP) induced by the Pt-water interaction governs the pH-dependent HOR kinetics on Pt(111). In alkali, the strong Pt-interfacial water electrostatic interaction behaves as a narrow OHP, which increases the proportion of "H-down" interfacial water and leads to less adsorbed water entering the inner Helmholtz plane (IHP), decreasing the work function of Pt(111). Furthermore, the more "H-down" interfacial water stabilizes the Had adsorption, prevents Had desorption, and suppresses the Volmer step of HOR by forming the solvated [Had···H2O···H2O] complex. Our work provided a visualized molecular-level mechanism to understand the nature of pH-dependent HOR kinetics.

Tailoring Interfacial Charge Transfer of Epitaxially Grown Ir Clusters for Boosting Hydrogen Oxidation Reaction

AbstractThe sluggish kinetics of hydrogen oxidation reaction (HOR) is one of the critical challenges for anion exchange membrane fuel cells. Here, we report epitaxial growth of Ir nanoclusters (<2 nm) on a MoS2 surface (Ir/MoS2) and optimize the alkaline HOR activity via tailoring interfacial charge transfer between Ir clusters and MoS2. The electron transfer from MoS2 to Ir clusters can effectively prevent the oxidation of Ir clusters, which is not the case for carbon‐supported Ir nanoclusters (Ir/C) synthesized using the same method. Moreover, the HOR performance of the Ir/MoS2 can be further optimized by tuning the hydrogen binding energy (HBE) via a precise annealing treatment. A substantial exchange current density of 1.28 mA cmECSA−2 is achieved in the alkaline medium, which is ∼10 times over that of Ir/C. The HOR mass‐specific activity of Ir/MoS2 heterostructure is as high as 182 mA mgIr−1. The experimental results and density functional theory calculations reveal that the significant improved HOR activity is attributed to the decreased HBE, which highlights epitaxial growth is an effective way for boosting catalytic activity of heterostructured catalysts.