How Size and Strain Effect Synergistically Improve Electrocatalytic Activity: A Systematic Investigation Based on PtCoCu Alloy Nanocrystals

To reveal how the size effect and strain effect synergistically regulate the mass activity (MA) and specific activity (SA) of Pt alloy nanocrystal catalysts in oxygen reduction reaction (ORR), remains to be difficult due to the highly entangled factors. In this work, six ternary PtCoCu catalysts with sequentially changed composition, size, and compression strain are prepared. It is found that the smaller the alloy particles, the higher the electrochemical active surface area (ECSA) and MA values, that is, the particle size plays a decisive role in the size of the ECSA and MA. While, along alloy size decrease, the intrinsic activity SA first increases, then remains unchanged, and finally rapidly increases again. This detailed analysis shows that for the alloys above 4 nm, it is the surface coordination number that decides the SA, while for those below 4 nm, it is the well-regulated compression strain that determines the SA. Particularly, Pt₄₇Co₂₆Cu₂₇ demonstrates the MA of 1.19 A mg_Pt⁻¹ and SA of 1.48 mA cm⁻², being 7.9 and 6.4 times those of commercial Pt/C respectively, representing an especially superior ORR catalyst.     

“Wiring” Fe‐Nx‐Embedded Porous Carbon Framework onto 1D Nanotubes for Efficient Oxygen Reduction Reaction in Alkaline and Acidic Media

This study presents a novel metal‐organic‐framework‐engaged synthesis route based on porous tellurium nanotubes as a sacrificial template for hierarchically porous 1D carbon nanotubes. Furthermore, an ultrathin Fe‐ion‐containing polydopamine layer has been introduced to generate highly effective FeN_xC active sites into the carbon framework and to induce a high degree of graphitization. The synergistic effects between the hierarchically porous 1D carbon structure and the embedded FeN_xC active sites in the carbon framework manifest in superior catalytic activity toward oxygen reduction reaction (ORR) compared to Pt/C catalyst in both alkaline and acidic media. A rechargeable zinc‐air battery assembled in a decoupled configuration with the nonprecious pCNT@Fe@GL/CNF ORR electrode and Ni‐Fe LDH/NiF oxygen evolution reaction (OER) electrode exhibits charge–discharge overpotentials similar to the counterparts of Pt/C ORR electrode and IrO₂ OER electrode.     

Self-Sacrificing Template Synthesis of Carbon Nanosheets Assembled Hollow Spheres with Abundant Active Fe–N4O1 Moieties for Electrocatalytic Oxygen Reduction

Single-atom Fe–N–C (Fe₁–N–C) materials represent the benchmarked electrocatalysts for oxygen reduction reaction (ORR). However, single Fe atoms in the carbon skeletons cannot be fully utilized due to the mass transfer limitation, severely restricting their intrinsic ORR properties. Herein, a self-sacrificing template strategy is developed to fabricate ultrathin nanosheets assembled Fe₁–N–C hollow microspheres (denoted as Fe₁/N-HCMs) by rational carbonization of Fe³⁺ chelating polydopamine coated melamine cyanuric acid complex. The shell of Fe₁/N-HCMs is constructed by ultrathin nanosheets with thickness of only 2 nm, which is supposed to be an ideal platform to isolate and fully expose single metal atoms. Benefiting from unique hierarchical hollow architecture with highly open porous structure, 2 nm-thick ultrathin nanosheet subunits and abundant Fe–N₄O₁ active sites revealed by X-ray absorption fine structure analysis, the Fe₁/N-HCMs exhibit high ORR performance with a positive half-wave potential of 0.88 V versus the reversible hydrogen electrode and robust stability. When served as air-cathode catalysts with ultralow loading mass of 0.25 mg cm⁻², Fe₁/N-HCMs based Zn–air batteries present a maximum power density of 187 mW cm⁻² and discharge specific capacity of 806 mA h g_Zn⁻¹ in primary Zn–air batteries, all exceeding those of commercial Pt/C.     

Stable High‐Index Faceted Pt Skin on Zigzag‐Like PtFe Nanowires Enhances Oxygen Reduction Catalysis

Selectively exposing active surfaces and judiciously tuning the near‐surface composition of electrode materials represent two prominent means of promoting electrocatalytic performance. Here, a new class of Pt₃Fe zigzag‐like nanowires (Pt‐skin Pt₃Fe z‐NWs) with stable high‐index facets (HIFs) and nanosegregated Pt‐skin structure is reported, which are capable of substantially boosting electrocatalysis in fuel cells. These unique structural features endow the Pt‐skin Pt₃Fe z‐NWs with a mass activity of 2.11 A mg^?1 and a specifc activity of 4.34 mA cm^?2 for the oxygen reduction reaction (ORR) at 0.9 V versus reversible hydrogen electrode, which are the highest in all reported PtFe‐based ORR catalysts. Density function theory calculations reveal a combination of exposed HIFs and formation of Pt‐skin structure, leading to an optimal oxygen adsorption energy due to the ligand and strain effects, which is responsible for the much enhanced ORR activities. In contrast to previously reported HIFs‐based catalysts, the Pt‐skin Pt₃Fe z‐NWs maintain ultrahigh durability with little activity decay and negligible structure transformation after 50 000 potential cycles. Overcoming a key technical barrier in electrocatalysis, this work successfully extends the nanosegregated Pt‐skin structure to nanocatalysts with HIFs, heralding the exciting prospects of high‐effcient Pt‐based catalysts in fuel cells.     

Ultrathin PtPd‐Based Nanorings with Abundant Step Atoms Enhance Oxygen Catalysis

The lack of highly active and stable catalysts with low Pt usage for the oxygen reduction reaction (ORR) is a major barrier in realizing fuel cell‐driven transportation applications. A general colloidal chemistry method is demonstrated for making a series of ultrathin PtPdM (M = Co, Ni, Fe) nanorings (NRs) for greatly boosting ORR catalysis. Different from the traditional ultrathin nanosheets, the ultrathin PtPdM NRs herein have a high portion of step atoms on the edge, high Pt utilization efficiency, and strong ligand effect from M to Pt and fast mass transport of reactants to the NRs. These key features make them exhibit greatly enhanced electrocatalytic activity for the ORR and the oxygen evolution reaction (OER). Among all the PtPdM NRs, the PtPdCo shows the highest ORR mass and specific activities of 3.58 A mg^?1 and 4.90 mA cm^?2 at 0.9 V versus reversible hydrogen electrode (RHE), 23.9 and 24.5‐fold larger than those of commercial Pt/C in alkaline electrolyte, respectively. The theoretical calculations reveal that the oxygen adsorption energy (E _O) can be optimized under the presence of step atoms exposed on the edge and ligand effect induced by Co. They are stable under ORR conditions with negligible changes after 30 000 cycles.     

Size‐Controlled Synthesis of Sub‐10 nm PtNi3 Alloy Nanoparticles and their Unusual Volcano‐Shaped Size Effect on ORR Electrocatalysis

Dealloyed Pt bimetallic core–shell catalysts derived from low‐Pt bimetallic alloy nanoparticles (e.g, PtNi₃) have recently shown unprecedented activity and stability on the cathodic oxygen reduction reaction (ORR) under realistic fuel cell conditions and become today's catalyst of choice for commercialization of automobile fuel cells. A critical step toward this breakthrough is to control their particle size below a critical value (≈10 nm) to suppress nanoporosity formation and hence reduce significant base metal (e.g., Ni) leaching under the corrosive ORR condition. Fine size control of the sub‐10 nm PtNi₃ nanoparticles and understanding their size dependent ORR electrocatalysis are crucial to further improve their ORR activity and stability yet still remain unexplored. A robust synthetic approach is presented here for size‐controlled PtNi₃ nanoparticles between 3 and 10 nm while keeping a constant particle composition and their size‐selected growth mechanism is studied comprehensively. This enables us to address their size‐dependent ORR activities and stabilities for the first time. Contrary to the previously established monotonic increase of ORR specific activity and stability with increasing particle size on Pt and Pt‐rich bimetallic nanoparticles, the Pt‐poor PtNi₃ nanoparticles exhibit an unusual “volcano‐shaped” size dependence, showing the highest ORR activity and stability at the particle sizes between 6 and 8 nm due to their highest Ni retention during long‐term catalyst aging. The results of this study provide important practical guidelines for the size selection of the low Pt bimetallic ORR electrocatalysts with further improved durably high activity.     

Sustainable Hydrothermal Carbonization Synthesis of Iron/Nitrogen‐Doped Carbon Nanofiber Aerogels as Electrocatalysts for Oxygen Reduction

It is urgent to develop new kinds of low‐cost and high‐performance nonprecious metal (NPM) catalysts as alternatives to Pt‐based catalysts for oxygen reduction reaction (ORR) in fuel cells and metal–air batteries, which have been proved to be efficient to meet the challenge of increase of global energy demand and CO₂ emissions. Here, an economical and sustainable method is developed for the synthesis of Fe, N codoped carbon nanofibers (Fe–N/CNFs) aerogels as efficient NPM catalysts for ORR via a mild template‐directed hydrothermal carbonization (HTC) process, where cost‐effective biomass‐derived d (+)‐glucosamine hydrochloride and ferrous gluconate are used as precursors and recyclable ultrathin tellurium nanowires are used as templates. The prepared Fe/N‐CNFs catalysts display outstanding ORR activity, i.e., onset potential of 0.88 V and half‐wave potential of 0.78 V versus reversible hydrogen electrode in an alkaline medium, which is highly comparable to that of commercial Pt/C (20 wt% Pt) catalyst. Furthermore, the Fe/N‐CNFs catalysts exhibit superior long‐term stability and better tolerance to the methanol crossover effect than the Pt/C catalyst in both alkaline and acidic electrolytes. This work suggests the great promise of developing new families of NPM ORR catalysts by the economical and sustainable HTC process.     

High‐Indexed PtNi Alloy Skin Spiraled on Pd Nanowires for Highly Efficient Oxygen Reduction Reaction Catalysis

The catalytic performance of Pt‐based catalysts for oxygen reduction reactions (ORR) can generally be enhanced by constructing high‐index exposed facets (HIFs). However, the synthesis of Pt alloyed high‐index skins on 1D non‐Pt surfaces to further improve Pt utilization and stability remains a fundamental challenge for practical nanocrystals. In this work, Pd nanowires (NWs) are selected as a rational medium to facilitate the epitaxial growth of Pt and Ni. Based on the different nucleation and growth habits of Pt and Ni, a continuous PtNi alloy skin bounded with HIFs spiraled on a Pd core can be obtained. Here, the as‐prepared helical Pd@PtNi NWs possess high HIF densities, low Pt contents, and optimized oxygen adsorption energies, demonstrating an enhanced ORR mass activity of 1.75 A mg_Pt^?1 and a specific activity of 3.18 mA cm^?2, which are 10 times and 12 times higher than commercial Pt/C catalysts, respectively. In addition, the 1D nanostructure enables the catalyst to be highly stable after 30 000 potential sweeping cycles. This work successfully extends bulky high‐indexed Pt alloys to core–shell nanostructures with the design of a new, highly efficient and stable Pt‐based catalyst for fuel cells.     

Effective size-controlled synthesis and electrochemical characterization of ordered Pt nanopattern arrays from self-assembling block copolymer template

This work offers an effective size-controlled synthesis of platinum nanoparticle (Pt NP) arrays for electrocatalyst through self-assembled nanopatterns of block copolymers on titanium (Ti) wafers. Size, spacing and uniformity of Pt NP with loading of Pt to a minimum were investigated to be controlled and adjusted in order to improve the electrochemically active surface area (ECSA) and ECSA stability, and Pt concentration in copolymer/chloroplatinic acid (H₂PtCl₆) solution was verified to be one of the most important factors to control the arrays’ structure. In our case, the Pt NPs with predictable size of 5–16.5 nm could be obtained when the Pt concentration is larger than 0.05 mg ml^?1, which the dominant diameter is proved to be proportional to one-third power of the Pt concentration according to the linear relation of templates’ Pt/N mass ratio versus Pt concentration, and the Pt NPs remain highly ordered arrays with predictable spacing when the Pt concentration is larger than 0.125 mg ml^?1. Decrease in Pt concentration from 2 to 0.125 mg ml^?1 is an effective method to improve the ECSA and durability simultaneously. The Pt NP arrays exhibit not only a remarkable initial ECSA value of 106.2 m² g^?1, but also a pseudo-zero particle aggregation possibility during 3000-cycle voltammetry, which is attributed to the high Pt NP dispersion and the ordered arrays that improve the Pt utilization and lower the possibility of aggregation.     

Mesoporous Nitrogen‐Doped Carbon‐Nanosphere‐Supported Isolated Single‐Atom Pd Catalyst for Highly Efficient Semihydrogenation of Acetylene

Semihydrogenation of acetylene in the ethylene feed is a vital step for the industrial production of polyethylene. Despite their favorable reaction activity and ethylene selectivity, the Pd‐based intermetallic compound and single‐atom alloy catalysts still suffer from the limitation of atomic utilization derived from the partial exposure of active Pd atoms. Herein, a hard‐template Lewis acid doping strategy is reported that can overcome the inefficient utilization of Pd atoms. In this strategy, N‐coordinated isolated single‐atomic Pd sites are fully embedded on the inner walls of mesoporous nitrogen‐doped carbon foam nanospheres (ISA‐Pd/MPNC). This synthetic strategy has been proved to be applicable to prepare other ISA‐M/MPNC (M = Pt and Cu) materials. This ISA‐Pd/MPNC catalyst with both high specific surface area (633.8 m² g^?1) and remarkably thin pore wall (1–2 nm) exhibits higher activity than that of its nonmesoporous counterpart (ISA‐Pd/non‐MPNC) catalyst by a factor of 4. This work presents an efficient way to tailor and optimize the catalytic activity and selectivity by atomic‐scale design and structural control.     

Active Sites and Mechanism of Oxygen Reduction Reaction Electrocatalysis on Nitrogen‐Doped Carbon Materials

The oxygen reduction reaction (ORR) is a core reaction for electrochemical energy technologies such as fuel cells and metal–air batteries. ORR catalysts have been limited to platinum, which meets the requirements of high activity and durability. Over the last few decades, a variety of materials have been tested as non‐Pt catalysts, from metal–organic complex molecules to metal‐free catalysts. In particular, nitrogen‐doped graphitic carbon materials, including N‐doped graphene and N‐doped carbon nanotubes, have been extensively studied. However, due to the lack of understanding of the reaction mechanism and conflicting knowledge of the catalytic active sites, carbon‐based catalysts are still under the development stage of achieving a performance similar to Pt‐based catalysts. In addition to the catalytic viewpoint, designing mass transport pathways is required for O₂. Recently, the importance of pyridinic N for the creation of active sites for ORR and the requirement of hydrophobicity near the active sites have been reported. Based on the increased knowledge in controlling ORR performances, bottom‐up preparation of N‐doped carbon catalysts, using N‐containing conjugative molecules as the assemblies of the catalysts, is promising. Here, the recent understanding of the active sites and the mechanism of ORRs on N‐doped carbon catalysts are reviewed.     

Modest Oxygen‐Defective Amorphous Manganese‐Based Nanoparticle Mullite with Superior Overall Electrocatalytic Performance for Oxygen Reduction Reaction

Manganese‐based oxides have exhibited high promise as noncoinage alternatives to Pt/C for catalyzing oxygen reduction reaction (ORR) in basic solution and a mix of Mn^3+/4+ valence is believed to be vital in achieving optimum ORR performance. Here, it is proposed that, distinct from the most studied perovskites and spinels, Mn‐based mullites with equivalent molar ratio of Mn³⁺ and Mn⁴⁺ provide a unique platform to maximize the role of Mn valence in facile ORR kinetics by introducing modest content of oxygen deficiency, which is also beneficial to enhanced catalytic activity. Accordingly, amorphous mullite SmMn₂O_5?δ nanoparticles with finely tuned concentration of oxygen vacancies are synthesized via a versatile top‐down approach and the modest oxygen‐defective sample with an Mn³⁺/Mn⁴⁺ ratio of 1.78, i.e., Mn valence of 3.36 gives rise to a superior overall ORR activity among the highest reported for the family of Mn‐based oxides, comparable to that of Pt/C. Altogether, this study opens up great opportunities for mullite‐based catalysts to be a cost‐effective alternative to Pt/C in diverse electrochemical energy storage and conversion systems.     

ZIF‐8/ZIF‐67‐Derived Co‐Nx‐Embedded 1D Porous Carbon Nanofibers with Graphitic Carbon‐Encased Co Nanoparticles as an Efficient Bifunctional Electrocatalyst

Herein, an approach is reported for fabrication of Co‐N_x‐embedded 1D porous carbon nanofibers (CNFs) with graphitic carbon‐encased Co nanoparticles originated from metal–organic frameworks (MOFs), which is further explored as a bifunctional electrocatalyst for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Electrochemical results reveal that the electrocatalyst prepared by pyrolysis at 1000 °C (CoNC‐CNF‐1000) exhibits excellent catalytic activity toward ORR that favors the four‐electron ORR process and outstanding long‐term stability with 86% current retention after 40 000 s. Meanwhile, it also shows superior electrocatalytic activity toward OER, reaching a lower potential of 1.68 V at 10 mA cm^?2 and a potential gap of 0.88 V between the OER potential (at 10 mA cm^?2) and the ORR half‐wave potential. The ORR and OER performance of CoNC‐CNF‐1000 have outperformed commercial Pt/C and most nonprecious‐metal catalysts reported to date. The remarkable ORR and OER catalytic performance can be mainly attributable to the unique 1D structure, such as higher graphitization degree beneficial for electronic mobility, hierarchical porosity facilitating the mass transport, and highly dispersed CoN_xC active sites functionalized carbon framework. This strategy will shed light on the development of other MOF‐based carbon nanofibers for energy storage and electrochemical devices.     

Colloidal Cobalt Phosphide Nanocrystals as Trifunctional Electrocatalysts for Overall Water Splitting Powered by a Zinc–Air Battery

Highly efficient and stable electrocatalysts, particularly those that are capable of multifunctionality in the same electrolyte, are in high demand for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). In this work, highly monodisperse CoP and Co₂P nanocrystals (NCs) are synthesized using a robust solution‐phase method. The highly exposed (211) crystal plane and abundant surface phosphide atoms make the CoP NCs efficient catalysts toward ORR and HER, while metal‐rich Co₂P NCs show higher OER performance owing to easier formation of plentiful Co₂P@COOH heterojunctions. Density functional theory calculation results indicate that the desorption of OH* from cobalt sites is the rate‐limiting step for both CoP and Co₂P in ORR and that the high content of phosphide can lower the reaction barrier. A water electrolyzer constructed with a CoP NC cathode and a Co₂P NC anode can achieve a current density of 10 mA cm^?2 at 1.56 V, comparable even to the noble metal‐based Pt/C and RuO₂/C pair. Furthermore, the CoP NCs are employed as an air cathode in a primary zinc–air battery, exhibiting a high power density of 62 mW cm^?2 and good stability.     

Facet-controlled Pt–Ir nanocrystals with substantially enhanced activity and durability towards oxygen reduction

Nanocrystals made of Pt–Ir alloys are fascinating catalysts towards the oxygen reduction reaction (ORR), but the lack of control over their surface atomic structures hinders further optimization of their catalytic performance. Here we report, for the first time, a class of highly active and durable ORR catalysts based on Pd@Pt–Ir nanocrystals with well-controlled facets. With an average of 1.6 atomic layers of a Pt₄Ir alloy on the surface, the nanocrystals can be made in cubic, octahedral, and icosahedral shapes to present Pt–Ir {1 0 0}, {1 1 1}, and {1 1 1} plus twin boundaries, respectively. The Pd@Pt–Ir nanocrystals exhibit not only facet-dependent catalytic properties but also substantially enhanced ORR activity and durability relative to a commercial Pt/C and their Pd@Pt counterparts. Among them, the Pd@Pt–Ir icosahedra deliver the best performance, with a mass activity of 1.88 A·mg⁻¹_Pt at 0.9 V, which is almost 15 times that of the commercial Pt/C. Our density functional theory (DFT) calculations attribute the high activity of the Pd@Pt–Ir nanocrystals, and the facet dependence of these activities, to easier protonation of O* and OH* under relevant OH* coverages, relative to the corresponding energetics on clean Pd@Pt surfaces. The DFT calculations also indicate that incorporating Ir atoms into the Pt lattice destabilizes OH–OH interactions on the surface, thereby raising the oxidation potential of Pt and greatly improving the catalytic durability.     

Zinc-Mediated Template Synthesis of Fe-N-C Electrocatalysts with Densely Accessible Fe-Nx Active Sites for Efficient Oxygen Reduction

Owing to their earth abundance, high atom utilization, and excellent activity, single iron atoms dispersed on nitrogen-doped carbons (Fe-N-C) have emerged as appealing alternatives to noble-metal platinum (Pt) for catalyzing the oxygen reduction reaction (ORR). However, the ORR activity of current Fe-N-C is seriously limited by the low density and inferior exposure of active Fe-N_x species. Here, a novel zinc-mediated template synthesis strategy is demonstrated for constructing densely exposed Fe-N_x moieties on hierarchically porous carbon (SA-Fe-NHPC). During the thermal treatment of 2,6-diaminopyridine/ZnFe/SiO₂ complex, the zinc prevents the formation of iron carbide nanoparticles and the SiO₂ template promotes the generation of hierarchically pores for substantially improving the accessibility of Fe-N_x moieties after subsequent leaching. As a result, the SA-Fe-NHPC electrocatalysts exhibit an unprecedentedly high ORR activity with a half-wave potential (E_1/2) of 0.93 V in a 0.1 m KOH aqueous solution, which outperforms those for Pt/C catalyst and state-of-the-art noble metal-free electrocatalysts. As the air electrode in zinc–air batteries, the SA-Fe-NHPC demonstrates a large peak power density of 266.4 mW cm⁻² and superior long-term stability. Therefore, the developed zinc-mediated template synthesis strategy for boosting the density and accessibility of Fe-N_x species paves a new avenue toward high-performance ORR electrocatalysts.     

Simultaneously Integrating Single Atomic Cobalt Sites and Co9S8 Nanoparticles into Hollow Carbon Nanotubes as Trifunctional Electrocatalysts for Zn–Air Batteries to Drive Water Splitting

The development of rechargeable metal–air batteries and water electrolyzers are highly constrained by electrocatalysts for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). However, the construction of efficient trifunctional electrocatalysts for ORR/OER/HER are highly desirable yet challenging. Herein, hollow carbon nanotubes integrated single cobalt atoms with Co₉S₈ nanoparticles (CoSA + Co₉S₈/HCNT) are fabricated by a straightforward in situ self‐sacrificing strategy. The structure of the CoSA + Co₉S₈/HCNT are verified by X‐ray absorption spectroscopy and aberration‐corrected scanning transmission electron microscopy. Theoretical calculations and experimental results embrace the synergistic effects between Co₉S₈ nanoparticles and single cobalt atoms through optimizing the electronic configuration of the CoN₄ active sites to lower the reaction barrier and facilitating the ORR, OER, and HER simultaneously. Consequently, rechargeable liquid and all‐solid‐state flexible Zn–air batteries based on CoSA + Co₉S₈/HCNT exhibit remarkable stability and excellent power density of 177.33 and 51.85 mW cm^?2, respectively, better than Pt/C + RuO₂ counterparts. Moreover, the as‐fabricated Zn–air batteries can drive an overall water splitting device assembled with CoSA + Co₉S₈/HCNT and achieve a current density of 10 mA cm^?2 at a low voltage of 1.59 V, also superior to Pt/C + RuO₂. Therefore, this work presents a promising approach to an efficient trifunctional electrocatalyst toward practical applications.     

Metal–Organic Framework‐Derived Bamboo‐like Nitrogen‐Doped Graphene Tubes as an Active Matrix for Hybrid Oxygen‐Reduction Electrocatalysts

In this work, large size (i.e., diameter > 100 nm) graphene tubes with nitrogen‐doping are prepared through a high‐temperature graphitization process of dicyandiamide (DCDA) and Iron(II) acetate templated by a novel metal–organic framework (MIL‐100(Fe)). The nitrogen‐doped graphene tube (N‐GT)‐rich iron‐nitrogen‐carbon (Fe‐N‐C) catalysts exhibit inherently high activity towards the oxygen reduction reaction (ORR) in more challenging acidic media. Furthermore, aiming to improve the activity and stability of conventional Pt catalysts, the ORR active N‐GT is used as a matrix to disperse Pt nanoparticles in order to build a unique hybrid Pt cathode catalyst. This is the first demonstration of the integration of a highly active Fe‐N‐C catalyst with Pt nanoparticles. The synthesized 20% Pt/N‐GT composite catalysts demonstrate significantly enhanced ORR activity and H₂‐air fuel cell performance relative to those of 20% Pt/C, which is mainly attributed to the intrinsically active N‐GT matrix along with possible synergistic effects between the non‐precious metal active sites and the Pt nanoparticles. Unlike traditional Pt/C, the hybrid catalysts exhibit excellent stability during the accelerated durability testing, likely due to the unique highly graphitized graphene tube morphologies, capable of providing strong interaction with Pt nanoparticles and then preventing their agglomeration.     

Biomass Derived N‐Doped Porous Carbon Supported Single Fe Atoms as Superior Electrocatalysts for Oxygen Reduction

Exploring sustainable and high‐performance electrocatalysts for the oxygen reduction reaction (ORR) is the crucial issue for the large‐scale application of fuel cell technology. A new strategy is demonstrated to utilize the biomass resource for the synthesis of N‐doped hierarchically porous carbon supported single‐atomic Fe (SA‐Fe/NHPC) electrocatalyst toward the ORR. Based on the confinement effect of porous carbon and high‐coordination natural iron source, SA‐Fe/NHPC, derived from the hemin‐adsorbed bio‐porphyra‐carbon by rapid heat‐treatment up to 800 °C, presents the atomic dispersion of Fe atoms in the N‐doped porous carbon. Compared with the molecular hemin and nanoparticle Fe samples, the as‐prepared SA‐Fe/NHPC exhibits a superior catalytic activity (E _1/2 = 0.87 V and J _k = 4.1 mA cm^?2, at 0.88 V), remarkable catalytic stability (≈1 mV negative shift of E _1/2, after 3000 potential cycles), and outstanding methanol‐tolerance, even much better than the state‐of‐the‐art Pt/C catalyst. The sustainable and effective strategy for utilizing biomass to achieve high‐performance single‐atom catalysts can also provide an opportunity for other catalytic applications in the atomic scale.     

Atomically Dispersed Ni–N4 Sites Assist Pt3Ni Nanocages with Pt Skin to Synergistically Enhance Oxygen Reduction Activity and Stability

Currently, the rarity and high cost of platinum (Pt)-based electrocatalysts seriously limit their commercial application in fuel cells cathode. Decorating Pt with atomically dispersed metal–nitrogen sites possibly offers an effective pathway to synergy tailor their catalytic activity and stability. Here active and stable oxygen reduction reaction (ORR) electrocatalysts (Pt₃Ni@Ni–N₄–C) by in situ loading Pt₃Ni nanocages with Pt skin on single-atom nickel–nitrogen (Ni–N₄) embedded carbon supports are designed and constructed. The Pt₃Ni@Ni–N₄–C exhibits excellent mass activity (MA) of 1.92 A mg_Pt⁻¹ and specific activity of 2.65 mA cm_Pt⁻², together with superior durability of 10 mV decay in half-wave potential and only 2.1% loss in MA after 30 000 cycles. Theoretical calculations demonstrate that Ni–N₄ sites significant redistribute of electrons and make them transfer from both the adjacent carbon and Pt atoms to the Ni–N₄. The resultant electron accumulation region successfully anchored Pt₃Ni, that not only improves structural stability of the Pt₃Ni, but importantly makes the surface Pt more positive to weaken the adsorption of *OH to enhance ORR activity. This strategy lays the groundwork for the development of super effective and durable Pt-based ORR catalysts.