Recent Development of Active Nanoparticle Catalysts for Fuel Cell Reactions

This review focuses on the recent advances in the synthesis of nanoparticle (NP) catalysts of Pt‐, Pd‐ and Au‐based NPs as well as composite NPs. First, new developments in the synthesis of single‐component Pt, Pd and Au NPs are summarized. Then the chemistry used to make alloy and composite NP catalysts aiming to enhance their activity and durability for fuel cell reactions is outlined. The review next introduces the exciting new research push in developing CoN/C and FeN/C as non‐Pt catalysts. Examples of size‐, shape‐ and composition‐dependent catalyses for oxygen reduction at cathode and formic acid oxidation at anode are highlighted to illustrate the potentials of the newly developed NP catalysts for fuel cell applications.     

Pt Dopant: Controlling the Ir Oxidation States toward Efficient and Durable Oxygen Evolution Reaction in Acidic Media

Dissolution of Ir oxides in Ir‐based catalysts, which is closely linked to the catalyst activity and stability toward the oxygen evolution reaction (OER) in acidic media, is a critical unresolved problem in the commercialization of water electrolysis. Doping foreign elements into the Ir oxides can accomplish an optimal combination of Ir oxidation states that is conducive to the leaching‐resistance of active catalytic sites. Here, it is reported that Pt doping into IrO_x‐based nanoframe is beneficial in both terms of activity and stability. The Pt‐doped IrO_x‐based nanoframe achieves the mass activity of 0.644 A mg^?1_Ir+Pt at 1.53 V_RHE, which is 15‐fold higher than that of the commercial IrO₂. During the accelerated durability test, the Ir^IV‐to‐Ir^III ratio of 5 is maintained in the presence of Pt dopant to effectively mitigate the degradation of Ir catalyst, leading to the superb catalyst durability in acidic media.     

“Ship‐in‐a‐Bottle” Growth of Noble Metal Nanostructures

Noble metal nanostructures are grown inside hollow mesoporous silica microspheres using “ship‐in‐a‐bottle” growth. Small Au seeds are first introduced into the interior of the hollow microspheres. Au nanorods with synthetically tunable longitudinal plasmon wavelengths and Au nanospheres are obtained through seed‐mediated growth within the microspheres. The encapsulated Au nanocrystals are further coated with Pd or Pt shells. The microsphere‐encapsulated bimetallic core/shell nanostructures can function as catalysts. They exhibit high catalytic performance and their stability is superior to that of the corresponding unencapsulated core/shell nanostructures in the catalytic oxidation of o‐phenylenediamine with hydrogen peroxide. Therefore, these hollow microsphere‐encapsulated metal nanostructures are promising as recoverable and efficient catalysts for various liquid‐phase catalytic reactions.     

Metal Nanocrystal‐Embedded Hollow Mesoporous TiO2 and ZrO2 Microspheres Prepared with Polystyrene Nanospheres as Carriers and Templates

Noble metal nanocrystals with different shapes and compositions are embedded in hollow mesoporous metal oxide microspheres through an ultrasonic aerosol spray. Polystyrene (PS) nanospheres are employed simultaneously as a hard template to create hollow interiors inside the oxide microspheres and as the carrier to bring pregrown metal nanocrystals, including Pd nanocubes, Au nanorods, and Au core/Pd shell nanorods, into the oxide microspheres. Calcination removes the PS template and causes the metal nanocrystals to adsorb on the inner surface of the hollow oxide microspheres. The catalytic performances of the Pd nanocube‐embedded TiO₂ and ZrO₂ microspheres are investigated using the reduction of 4‐nitrophenol as a model reaction. The presence of the mesopores in the oxide microspheres allows the reactant molecules to diffuse into the hollow interiors and subsequently interact with the Pd nanocubes. The embedding of the metal nanocrystals in the hollow oxide microspheres prevents the aggregation of the metal nanocrystals and reduces the loss of the catalyst during recycling. The Pd nanocube‐embedded ZrO₂ microspheres are found to exhibit a much higher catalytic activity, a much larger catalytic reaction rate, and a superior recyclability in comparison with a commercial Pd/C catalyst. This preparation approach could potentially be utilized to incorporate various types of mono‐ and multimetallic nanocrystals with different sizes, shapes, and compositions into hollow mesoporous oxide microspheres. Such a capability can facilitate the studies of the catalytic properties of various combinations of metal nanocrystals and metal oxide supports and therefore guide the design and creation of high‐performance catalysts.     

A Core‐Shell Nanoporous Pt‐Cu Catalyst with Tunable Composition and High Catalytic Activity

Composition‐controlled fabrication of bimetallic catalysts is of significance in electrochemical energy conversion and storage. A novel nanoporous Pt‐Cu bimetallic catalyst with a Pt skin and a Pt‐Cu core, fabricated by electrochemically dealloying a bulk Pt‐Cu binary alloy using a potential‐controlled approach, is reported. The Pt/Cu ratio of the dealloyed nanoporous catalyst can be readily adjusted in a wide composition range by only controlling dealloying potential. The electro‐catalytic performance of the nanoporous Pt‐Cu catalyst shows evident dependence on Pt/Cu ratio although the surfaces of all the nanoporous catalysts are characterized to be covered by pure Pt. With optimal compositions, the dealloyed nanoporous Pt‐Cu catalyst possesses enhanced electrocatalytic activities toward oxygen reduction reaction and formic acid oxidation in comparison with the commercial Pt/C catalyst.     

Formation of Gold and Silver Nanoparticle Arrays and Thin Shells on Mesostructured Silica Nanofibers

Mesostructured silica nanofibers synthesized in high yields with cetyltrimethylammonium bromide as the structure‐directing agent in HBr solutions are used as templates for the assembly of Au and Ag nanoparticles and the formation of thin Au shells along the fiber axis. Presynthesized spherical Au and Ag nanoparticles are adsorbed in varying amounts onto the silica nanofibers through bifunctional linking molecules. Nonspherical Au nanoparticles with sharp tips are synthesized on the nanofibers through a seed‐mediated growth approach. The number density of nonspherical Au nanoparticles is controlled by varying the amount of seeded nanofibers relative to the amount of supplied Au precursor. This seed‐mediated growth is further used to form continuous Au shells around the silica nanofibers. Both the Au‐ and Ag‐nanoparticle/silica‐nanofiber hybrid nanostructures and silica/Au core/shell fibers exhibit extinction spectra that are distinct from the spectra of Au and Ag nanoparticles in solution, indicating the presence of new surface plasmon resonance modes in the silica/Au core/shell fibers and surface plasmon coupling between closely spaced metal nanoparticles assembled on silica nanofibers. Spherical Au‐ and Ag‐nanoparticle/silica‐nanofiber hybrid nanostructures are further used as substrates for surface‐enhanced Raman spectroscopy, and the enhancement factors of the Raman signals obtained on the Ag‐nanoparticle/silica‐nanofiber hybrid nanostructures are 2 × 10⁵ for 4‐mercaptobenzoic acid and 4‐mercaptophenol and 7 × 10⁷ for rhodamine B isothiocyanate. These hybrid nanostructures are therefore potentially useful for ultrasensitive chemical and biological sensing by using molecular vibrational signatures.     

Replicating the Defect Structures on Ultrathin Rh Nanowires with Pt to Achieve Superior Electrocatalytic Activity toward Ethanol Oxidation

Metal nanostructures with an ultrathin Pt skin and abundant surface defects are attractive for electrocatalytic applications owing to the increased utilization efficiency of Pt atoms and the presence of highly reactive sites. This paper reports a conformal, layer‐by‐layer deposition of Pt atoms on defective Rh nanowires for the faithful replication of surface defects (i.e., grain boundaries) on the Rh nanowires. The thickness of the Pt shell can be controlled from one monolayer up to 5.3 atomic layers. This series of Rh@Pt_nL (n = 1–5.3) core–sheath nanowires show greatly enhanced activity and durability in catalyzing the ethanol oxidation reaction in an acidic medium. Among others, the Rh @ Pt_3.5L nanowires show the greatest mass activity (809 mA mg^?1_Pt) and specific activity (1.18 mA cm^?2) after loaded on carbon support, which are 3.7 and 3.4 times those of the commercial Pt/C, respectively. In situ Fourier transform infrared spectroscopy studies indicate an enhanced interaction between the outermost Pt layer and the Rh nanowire can promote C? C bond cleavage for complete oxidation of ethanol to CO₂ while depress the dehydrogenation of ethanol to acetic acid. As the Pt shell thickness is increased, the selectivity for the CO₂ pathway decreases while that for acetic acid is increased.     

Hollow Loofah‐Like N,O‐Co‐Doped Carbon Tube for Electrocatalysis of Oxygen Reduction

Designing a highly active doped‐carbon‐based oxygen reduction reaction (ORR) electrocatalyst with optimal stability is a must if large‐scale implementations of fuel cells are to be realized. Developing controllable doping strategies is essential for achieving highly active catalysts. Herein, a facile doping strategy is developed by designing a precursor material with unique core–shell nanostructure, whereby the Materials Institute Lavoisier (MIL) metal–organic framework (MOF) and polyaniline are core and shell components, and serving as oxygen and nitrogen precursors, respectively. A novel hollow loofah‐like carbon tube (HLCT) catalyst is derived from precursor material with controllable heteroatom‐doping concentrations through modulating the mass ratio of MOF/aniline. The optimal HLCT‐1/2 catalyst, with a MOF/aniline mass ratio of 1/2, exhibits excellent ORR activity and stability in an alkaline medium. Remarkably, the half‐wave potential (0.88 V) and the current density (4.35 mA cm^?2) at 0.85 V of HLCT‐1/2 catalyst surpass that of commercial Pt/C. Such superior catalytic properties can be attributed to the high specific surface area and abundant active sites of loofah‐shape carbon tubes. Moreover, the O dopant modulates the content and distribution of N species, leading to the enhanced adsorption strength of oxygen molecules on catalyst surface, promoting the activation of oxygen, and thus achieving higher electrocatalytic activity.     

Improved Hydrogen Production of Au–Pt–CdS Hetero‐Nanostructures by Efficient Plasmon‐Induced Multipathway Electron Transfer

The design of new functional materials with excellent hydrogen production activity under visible‐light irradiation has critical significance for solving the energy crisis. A well‐controlled synthesis strategy is developed to prepare an Au–Pt–CdS hetero‐nanostructure, in which each component of Au, Pt, and CdS has direct contact with the other two materials; Pt is on the tips and a CdS layer along the sides of an Au nanotriangle (NT), which exhibits excellent photocatalytic activity for hydrogen production under light irradiation (λ > 420 nm). The sequential growth and surfactant‐dependent deposition produce the three‐component Au–Pt–CdS hybrids with the Au NT acting as core while Pt and CdS serve as a co‐shell. Due to the presence of the Au NT cores, the Au–Pt–CdS nanostructures possess highly enhanced light‐harvesting and strong local‐electric‐field enhancement. Moreover, the intimate and multi‐interface contact generates multiple electron‐transfer pathways (Au to CdS, CdS to Pt and Au to Pt) which guide photoexcited electrons to the co‐catalyst Pt for an efficient hydrogen reduction reaction. By evaluating the hydrogen production rate when aqueous Na₂SO₃–Na₂S solution is used as sacrificial agent, the Au–Pt–CdS hybrid exhibits excellent photocatalytic activity that is about 2.5 and 1.4 times larger than those of CdS/Pt and Au@CdS/Pt, respectively.     

Template Synthesis of Aligned Carbon Nanotube Arrays using Glucose as a Carbon Source: Pt Decoration of Inner and Outer Nanotube Surfaces for Fuel‐Cell Catalysts

A facile method is developed to synthesize aligned arrays of open‐ended carbon nanotubes (CNTs) via in situ glucose polymerization in the inner pores of anodic aluminum oxide templates under hydrothermal conditions, followed by carbonization at high temperature. Pt nanoparticles are decorated on the surfaces of the as‐prepared CNTs using the incipient wet method based on the use of NaBH₄ as a reductant. Characterization of the resulting structures by transmission electron microscopy and field‐emission scanning electron microscopy demonstrates that the Pt nanoparticles are anchored on both the inner and outer walls of CNTs, thus giving rise to a shell–core–shell‐like nanotube composite. The electrocatalytic properties of the Pt–CNT–Pt electrodes are investigated for methanol oxidation by cyclic voltammetry and chronoamperometric measurements. It is found that the hybrid electrodes show superior catalytic performance compared to commercial carbon‐black‐supported Pt. The increased catalytic efficiency of Pt might be a result of the unique morphology of these structures.     

Plasmon‐Induced Hot Carrier Separation across Dual Interface in Gold–Nickel Phosphide Heterojunction for Photocatalytic Water Splitting

Precise control of the topology of metal nanocrystals and appropriate modulation of the metal–semiconductor heterostructure is an important way to understand the relationship between structure and material properties for plasmon‐induced solar‐to‐chemical energy conversion. Here, a bottom‐up wet chemical approach to synthesize Au/Ni₂P heterostructures via Pt‐catalyzed quasi‐epitaxial overgrowth of Ni on Au nanorods (NR) is presented. The structural motif of the Ni₂P is controlled using the aspect ratio of the Au NR and the effective micelle concentration of the C₁₆TAB capping agent. Highly ordered Au/Pt/Ni₂P nanostructures are employed as the photoelectrocatalytic anode system for water splitting. Electrochemical and ultrafast absorption spectroscopy characterization indicates that the structural motif of the Ni₂P (controlled by the outer‐shell deposition of Ni) helps to manipulate hot electron transfer during surface plasmon decay. With optimized Ni₂P thickness, Pt‐tipped Au NR with an aspect ratio of 5.2 exhibits a geometric current density of 10 mA cm^?2 with an overpotential of 140 mV. The photoanode displays unprecedented long‐term stability with continuous chronoamperometric performance of 50 h at an input potential of 1.5 V with over 30 days. This work provides definitive guidance for designing plasmonic–catalytic nanomaterials for enhanced solar‐to‐chemical energy conversion.     

Molecular Engineering of Noble Metal Aerogels Boosting Electrocatalytic Oxygen Reduction

Developing robust oxygen reduction reaction (ORR) electrocatalysts with high activity and durability remains great challenging while noble metal aerogels (NMAs) hold great potential because of their hierarchically porous morphology, excellent activity, and self-supported characteristic. Herein, a general molecular engineering strategy to synthesize molecule-noble metal aerogels (M-NMAs) via 3D assembly of metal nanoparticles (e.g., Pt, Pd, Au, Ag, and PtPd NPs) induced by metalloporphyrin as cross-linkers is reported. Due to the well synergy of NMAs and porphyrin molecule in creating the facile reaction pathway for ORR catalysis, these M-NMAs demonstrate boosted ORR activity and durability in different electrolytes. Particularly, the best PtPd-based M-NMA delivers 1.47 A mg_Pt⁻¹ and 2.13 mA cm⁻² in mass and specific activities, which are 11.3 and 14.2 times higher than those of the commercial Pt/C catalyst, respectively. Thus, this work not only provides a simple and universal functional engineering approach of NMAs with catalytic molecules, but also opens an avenue of the rational design for superior ORR electrocatalysts.     

Self‐Catalyzed Growth of Co,N‐Codoped CNTs on Carbon‐Encased CoSx Surface: A Noble‐Metal‐Free Bifunctional Oxygen Electrocatalyst for Flexible Solid Zn–Air Batteries

The self‐catalyzed growth of nanostructures on material surfaces is one of the most time‐ and cost‐effective ways to design multifunctional catalysts for a wide range of applications. Herein, the use of this technique to develop a multicomponent composite catalyst with CoS_x core encapsulated in an ultrathin porous carbon shell entangled with Co, N‐codoped carbon nanotubes is reported. The as‐prepared catalyst has a superior catalytic activity for oxygen evolution and oxygen reduction reactions, an ultralow potential gap of 0.74 V, and outstanding durability, surpassing most previous reports. Such superiority is ascribed, in part, to the unique 3D electrode architecture of the composite, which is favorable for transporting oxygen species and electrons and creates a synergy between the components with different functionalities. Moreover, the flexible solid Zn–air battery assembled with such an air electrode shows a steady discharge voltage plateau of 1.25 V and a round‐trip efficiency of 70% at 1 mA cm^?2. This work presents a simple strategy to design highly efficient bifunctional oxygen electrocatalysts and may pave the way for the practical application of these materials in many energy conversion/storage devices.     

Tungsten‐Doping‐Induced Surface Reconstruction of Porous Ternary Pt‐Based Alloy Electrocatalyst for Oxygen Reduction

Surface engineering has been found to be effective in promoting the catalytic activities of noble‐metal‐based nanocatalysts. In this contribution, by using the PtCu_xNi ternary alloy nanocrystal (NC) as the model catalyst, a surface tungsten(W)‐doping strategy, combining a surface oxidative acid treatment protocol, can effectively boost the electrocatalytic activities of the NCs in oxygen reduction reaction. The W‐doped PtCu_xNi alloy catalysts show obvious enhancement in electrochemical surface area and mass activity and slightly enhanced specific activity compared with the undoped catalyst. Based on the experimental evidence, it is proposed that the W doping involves a surface reconstruction by first removing the surface Pt atoms from the NC and then reducing them back to the surface. The existence of surface Ni atoms may be crucial in promoting the catalytic activities possibly through their electronic interactions to the active sites. The durability of the W‐doped PtCu_xNi catalysts is also enhanced possibly due to the pinning effect of surface W atoms. Therefore, the surface engineering of PtCu_xNi ternary alloy by W atoms can effectively modulate its activity and durability.     

An Advanced Nitrogen‐Doped Graphene/Cobalt‐Embedded Porous Carbon Polyhedron Hybrid for Efficient Catalysis of Oxygen Reduction and Water Splitting

A novel hybrid electrocatalyst consisting of nitrogen‐doped graphene/cobalt‐embedded porous carbon polyhedron (N/Co‐doped PCP//NRGO) is prepared through simple pyrolysis of graphene oxide‐supported cobalt‐based zeolitic imidazolate‐frameworks. Remarkable features of the porous carbon structure, N/Co‐doping effect, introduction of NRGO, and good contact between N/Co‐doped PCP and NRGO result in a high catalytic efficiency. The hybrid shows excellent electrocatalytic activities and kinetics for oxygen reduction reaction in basic media, which compares favorably with those of the Pt/C catalyst, together with superior durability, a four‐electron pathway, and excellent methanol tolerance. The hybrid also exhibits superior performance for hydrogen evolution reaction, offering a low onset overpotential of 58 mV and a stable current density of 10 mA cm^?2 at 229 mV in acid media, as well as good catalytic performance for oxygen evolution reaction (a small overpotential of 1.66 V for 10 mA cm^?2 current density). The dual‐active‐site mechanism originating from synergic effects between N/Co‐doped PCP and NRGO is responsible for the excellent performance of the hybrid. This development offers an attractive catalyst material for large‐scale fuel cells and water splitting technologies.     

Synergistically Enhanced Oxygen Reduction Electrocatalysis by Subsurface Atoms in Ternary PdCuNi Alloy Catalysts

For Pd‐based alloy catalysts, the selection of metallic alloying elements and the construction of composition‐gradient surface and subsurface layers are critical in achieving superior electrocatalytic activities in, e.g., the oxygen reduction reaction (ORR). Based on the Pd‐containing alloy, highly monodispersed PdCuNi ternary alloy nanocrystals are prepared through a wet‐chemical approach, and a solution‐based oxidative surface treatment protocol is utilized to activate the surface of the nanocrystals. A drastically enhanced ORR activity can be achieved by removing the surface Ni and Cu atoms through the surface treatment protocol. The treated catalyst demonstrates a mass activity of 0.45 A mg_Pd^?1 in alkaline medium, 5 and 2.4 times those of commercial Pt/C and Pd/C, respectively. The first‐principle calculation result suggests the critical roles of the coexistence of Ni and Cu atoms and their synergistic interaction beneath the outmost pure Pd layer in optimizing the oxygen binding energy for ORR. The calculation also suggests that the optimal binding energy of oxygen requires an appropriate Ni/Cu ratio in the subsurface layer. This work demonstrates a class of high‐performance Pt‐free ternary alloy ORR catalysts and may provide a general guideline for the structural design of Pd‐based ternary alloy catalysts.     

Localized Surface Plasmon Resonance Enhanced Photocatalytic Hydrogen Evolution via Pt@Au NRs/C3N4 Nanotubes under Visible‐Light Irradiation

Au nanorods (NRs) decorated carbon nitride nanotubes (Au NRs/CNNTs) photocatalysts have been designed and prepared by impregnation–annealing approach. Localized surface plasmon resonance (LSPR) peaks of Au NRs can be adjusted by changing the aspect ratios, and the light absorption range of Au NRs/CNNTs is extended to longer wavelength even near‐infrared light. Optimal composition of Pt@Au NR₇₆₉/CNNT₆₅₀ has been achieved by adjusting the LSPR peaks of Au NRs and further depositing Pt nanoparticles (NPs), and the photocatalytic H₂ evolution rate is 207.0 µmol h^?1 (20 mg catalyst). Preliminary LSPR enhancement photocatalytic mechanism is suggested. On one hand, LSPR of Au NRs is beneficial for visible‐light utilization. On the other hand, Pt NPs and Au NRs have a synergetic enhancement effect on photocatalytic H₂ evolution of CNNTs, in which the local electromagnetic field can improve the photogenerated carrier separation and direct electron transfer increases the hot electron concentration while Au NRs as the electron channel can well restrain charge recombination, finally Pt as co‐catalyst can boost H⁺ reduction rate. This work provides a new way to develop efficient photocatalysts for splitting water, which can simultaneously extend light absorption range and facilitate carrier generation, transportation and reduce carrier recombination.     

PtCo@NCs with Short Heteroatom Active Site Distance for Enhanced Catalytic Properties

The crucial issue for fuel cells is to improve the activity and durability of Pt‐based catalysts. Herein, based on the short distance enhancement effects, a novel PtCo@NC catalyst with remarkably enhanced electrocatalytic properties for methanol oxidation reaction (MOR) in acidic electrolytes is developed by shortening the Pt–Co active site distance. In brief, a series of PtCo@NC catalysts with different Pt–Co biatomic arrangement are precisely synthesized by an in situ reduction‐fusion method, achieving Pt–Co structural evolution from a Pt/Co individual monometallic islet (A‐700 °C) to PtCo heterodimer (A‐800 °C) and then a PtCo alloy (A‐900 °C) embedded on nitrogen‐doped carbon matrixes. Compared with the Pt/Co monometallic islet and heterodimer, the PtCo@NC (A‐900 °C) with the shortest Pt–Co active site distance exhibits the highest mass activity of 2.30 A mg_Pt^?1, which is 12.23 times higher than that of commercial Pt/C and exceeds almost all the reported MOR catalysts in acidic electrolytes. Both experiments and density functional theory calculations reveal that the remarkably improved activity stems from the modification of electron distribution around Pt/Co metal centers, thus promoting the rate‐determining methanol dehydrogenation step and CO oxidative removal processes, which are dependent on the distance between bimetallic active sites.     

Ultrahigh Mass Activity for the Hydrogen Evolution Reaction by Anchoring Platinum Single Atoms on Active {100} Facets of TiC via Cation Defect Engineering

Improving the platinum (Pt) mass activity for low-cost electrochemical hydrogen evolution is an important and arduous task. Here, a selective etching-reducing fluidized bed reactor technique is reported to create Ti vacancies and firmly anchor single Pt atoms on the active {100} facets of titanium carbide (TiC) to increase the Pt utilization efficiency and improve catalytic activity significantly by a synergistic effect between Ti vacancies and Pt atoms. The generated Ti vacancies are negatively charged and stabilize Pt atoms by forming covalent Pt C bonds, showing excellent long-term durability. Pt single atoms (ultralow load of 1.2 µg cm⁻²) on the defective TiC {100} show remarkable activity (24.9 mV at 10 mA cm⁻²) and a mass activity (49.69 A mg⁻¹) ≈190 times that of the state-of-the-art Pt C catalyst and nearly double the previously reported best values. The developed cation defect engineering exhibits excellent potential for fabricating next-generation advanced single-atom catalysts for large-scale hydrogen evolution at a low cost.     

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

Developing 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.