High-Volumetric Density Atomic Cobalt on Multishell ZnxCd1-xS Boosts Photocatalytic CO2 Reduction.

The volumetric density of the metal atomic site is decisive to the operating efficiency of the photosynthetic nanoreactor, yet its rational design and synthesis remain a grand challenge. Herein, we report a shell-regulating approach to enhance the volumetric density of Co atomic sites onto/into multishell ZnxCd1-xS for greatly improving CO2 photoreduction activity. We first establish a quantitative relation between the number of shell layers, specific surface areas, and volumetric density of atomic sites on multishell ZnxCd1-xS and conclude a positive relation between photosynthetic performance and the number of shell layers. The triple-shell ZnxCd1-xS-Co1 achieves the highest CO yield rate of 7629.7 µmol g-1 h-1, superior to those of the double-shell ZnxCd1-xS-Co1 (5882.2 µmol g-1 h-1) and single-shell ZnxCd1-xS-Co1 (4724.2 µmol g-1 h-1). Density functional theory calculations suggest that high-density Co atomic sites can promote the mobility of photogenerated electrons and enhance the adsorption of Co(bpy)32+ to increase CO2 activation (CO2 → CO2* → COOH* → CO* → CO) via the S-Co-bpy interaction, thereby enhancing the efficiency of photocatalytic CO2 reduction.

Single-atom Mo-tailored high-entropy-alloy ultrathin nanosheets with intrinsic tensile strain enhance electrocatalysis.

The precise structural integration of single-atom and high-entropy-alloy features for energy electrocatalysis is highly appealing for energy conversion, yet remains a grand challenge. Herein, we report a class of single-atom Mo-tailored PdPtNiCuZn high-entropy-alloy nanosheets with dilute Pt-Pt ensembles and intrinsic tensile strain (Mo1-PdPtNiCuZn) as efficient electrocatalysts for enhancing the methanol oxidation reaction catalysis. The as-made Mo1-PdPtNiCuZn delivers an extraordinary mass activity of 24.55 A mgPt-1 and 11.62 A mgPd+Pt-1, along with impressive long-term durability. The planted oxophilic Mo single atoms as promoters modify the electronic structure of isolated Pt sites in the high-entropy-alloy host, suppressing the formation of CO adsorbates and steering the reaction towards the formate pathway. Meanwhile, Mo promoters and tensile strain synergistically optimize the adsorption behaviour of intermediates to achieve a more energetically favourable pathway and minimize the methanol oxidation reaction barrier. This work advances the design of atomically precise catalytic sites by creating a new paradigm of single atom-tailored high-entropy alloys, opening an encouraging pathway to the design of CO-tolerance electrocatalysts.

Selective Electrified Propylene-to-Propylene Glycol Oxidation on Activated Rh-Doped Pd.

Renewable-energy-powered electrosynthesis has the potential to contribute to decarbonizing the production of propylene glycol, a chemical that is used currently in the manufacture of polyesters and antifreeze and has a high carbon intensity. Unfortunately, to date, the electrooxidation of propylene under ambient conditions has suffered from a wide product distribution, leading to a low faradic efficiency toward the desired propylene glycol. We undertook mechanistic investigations and found that the reconstruction of Pd to PdO occurs, followed by hydroxide formation under anodic bias. The formation of this metastable hydroxide layer arrests the progressive dissolution of Pd in a locally acidic environment, increases the activity, and steers the reaction pathway toward propylene glycol. Rh-doped Pd further improves propylene glycol selectivity. Density functional theory (DFT) suggests that the Rh dopant lowers the energy associated with the production of the final intermediate in propylene glycol formation and renders the desorption step spontaneous, a concept consistent with experimental studies. We report a 75% faradic efficiency toward propylene glycol maintained over 100 h of operation.

Assembled RhRuFe Trimetallene for Water Electrolysis.

Industrializing water electrolyzers demands better electrocatalysts, especially for the anodic oxygen evolution reaction (OER). The prevailing OER catalysts are Ir or Ru-based nanomaterials, however, they still suffer from insufficient stability. An alternative yet considerably less explored approach is to upgrade Rh, a known stable but moderately active element for OER electrocatalysis, via rational structural engineering. Herein, a precise synthesis of assembled RhRuFe trimetallenes (RhRuFe TMs) with an average thickness of 1 nm for boosting overall water splitting catalysis is reported. Favorable mass transport and optimized electronic structure collectively render RhRuFe TMs with an improved OER activity of an overpotential of 330 mV to deliver 10 mA cm-2, which is significantly lower than the Rh/C control (by 601 mV) and reported Rh-based OER electrocatalysts. In particular, the RhRuFe TMs-based water splitting devices can achieve the current density of 10 mA cm-2 at a low voltage of 1.63 V, which is among the best in the Rh-based bifunctional catalysts for electrolyzers. The addition of Fe in RhRuFe TMs can modulate the strain/electron distribution of the multi-alloy, which regulates the binding energies of H* and OH* in hydrogen and oxygen evolution reactions for achieving the enhanced bifunctional OER and HER catalysis is further demonstrated.

Site-specific reactivity of stepped Pt surfaces driven by stress release.

Heterogeneous catalysts are widely used to promote chemical reactions. Although it is known that chemical reactions usually happen on catalyst surfaces, only specific surface sites have high catalytic activity. Thus, identifying active sites and maximizing their presence lies at the heart of catalysis research1-4, in which the classic model is to categorize active sites in terms of distinct surface motifs, such as terraces and steps1,5-10. However, such a simple categorization often leads to orders of magnitude errors in catalyst activity predictions and qualitative uncertainties of active sites7,8,11,12, thus limiting opportunities for catalyst design. Here, using stepped Pt(111) surfaces and the electrochemical oxygen reduction reaction (ORR) as examples, we demonstrate that the root cause of larger errors and uncertainties is a simplified categorization that overlooks atomic site-specific reactivity driven by surface stress release. Specifically, surface stress release at steps introduces inhomogeneous strain fields, with up to 5.5% compression, leading to distinct electronic structures and reactivity for terrace atoms with identical local coordination, and resulting in atomic site-specific enhancement of ORR activity. For the terrace atoms flanking both sides of the step edge, the enhancement is up to 50 times higher than that of the atoms in the middle of the terrace, which permits control of ORR reactivity by either varying terrace widths or controlling external stress. Thus, the discovery of the above synergy provides a new perspective for both fundamental understanding of catalytically active atomic sites and design principles of heterogeneous catalysts.

Strong d-π Orbital Coupling of Co-C4 Atomic Sites on Graphdiyne Boosts Potassium-Sulfur Battery Electrocatalysis.

Potassium-sulfur (K-S) batteries are severely limited by the sluggish kinetics of the solid-phase conversion of K2S3/K2S2 to K2S, the rate-determining and performance-governing step, which urgently requires a cathode with facilitated sulfur accommodation and improved catalytic efficiency. To this end, we leverage the orbital-coupling approach and herein report a strong d-π coupling catalytic configuration of single-atom Co anchored between two alkynyls of graphdiyne (Co-GDY). The d-π orbital coupling of the Co-C4 moiety fully redistributes electrons two-dimensionally across the GDY, and as a result, drastically accelerates the solid-phase K2S3/K2S2 to K2S conversion and enhances the adsorption of sulfur species. Applied as the cathode, the S/Co-GDY delivered a record-high rate performance of 496.0 mAh g-1 at 5 A g-1 in K-S batteries. In situ and ex situ characterizations coupling density functional theory (DFT) calculations rationalize how the strong d-π orbital coupling of Co-C4 configuration promotes the reversible solid-state transformation kinetics of potassium polysulfide for high-performance K-S batteries.

Carbon-Extraction-Induced Biaxial Strain Tuning of Carbon-Intercalated Iridium Metallene for Hydrogen Evolution Catalysis.

Metallene materials with atomic thicknesses are receiving increasing attention in electrocatalysis due to ultrahigh surface areas and distinctive surface strain. However, the continuous strain regulation of metallene remains a grand challenge. Herein, taking advantage of autocatalytic reduction of Cu2+ on biaxially strained, carbon-intercalated Ir metallene, we achieve control over the carbon extraction kinetics, enabling fine regulation of carbon intercalation concentration and continuous tuning of (111) in-plane (-2.0%-2.6%) and interplanar (3.5%-8.8%) strains over unprecedentedly wide ranges. Electrocatalysis measurements reveal the strain-dependent activity toward hydrogen evolution reaction (HER), where weakly strained Ir metallene (w-Ir metallene) with the smallest lattice constant presents the highest mass activity of 2.89 A mg-1Ir at -0.02 V vs reversible hydrogen electrode (RHE). Theoretical calculations validated the pivotal role of lattice compression in optimizing H binding on carbon-intercalated Ir metallene surfaces by downshifting the d-band center, further highlighting the significance of strain engineering for boosted electrocatalysis.

Low-Electronegativity Mn-Contraction of PtMn Nanodendrites Boosts Oxygen Reduction Durability.

Platinum metal (PtM, M=Ni, Fe, Co) alloys catalysts show high oxygen reduction reaction (ORR) activity due to their well-known strain and ligand effects. However, these PtM alloys usually suffer from a deficient ORR durability in acidic environment as the alloyed metal is prone to be dissolved due to its high electronegativity. Herein, we report a new class of PtMn alloy nanodendrite catalyst with low-electronegativity Mn-contraction for boosting the oxygen reduction durability of fuel cells. The moderate strain in PtMn, induced by Mn contraction, yields optimal oxygen reduction activity at 0.53 A mg-1 at 0.9 V versus reversible hydrogen electrode (RHE). Most importantly, we show that relative to well-known high-electronegativity Ni-based Pt alloy counterpart, the PtMn nanodendrite catalyst experiences less transition metals' dissolution in acidic solution and achieves an outstanding mass activity retention of 96 % after 10,000 degradation cycles. Density functional theory calculation reveals that PtMn alloys are thermodynamically more stable than PtNi alloys in terms of formation enthalpy and cohesive energy. The PtMn nanodendrite-based membrane electrode assembly delivers an outstanding peak power density of 1.36 W cm-2 at a low Pt loading and high-performance retention over 50 h operations at 0.6 V in H2 -O2 hydrogen fuel cells.

Intermetallic Nanocrystals for Fuel-Cells-Based Electrocatalysis.

Electrocatalysis underpins the renewable electrochemical conversions for sustainability, which further replies on metallic nanocrystals as vital electrocatalysts. Intermetallic nanocrystals have been known to show distinct properties compared to their disordered counterparts, and been long explored for functional improvements. Tremendous progresses have been made in the past few years, with notable trend of more precise engineering down to an atomic level and the investigation transferring into more practical membrane electrode assembly (MEA), which motivates this timely review. After addressing the basic thermodynamic and kinetic fundamentals, we discuss classic and latest synthetic strategies that enable not only the formation of intermetallic phase but also the rational control of other catalysis-determinant structural parameters, such as size and morphology. We also demonstrate the emerging intermetallic nanomaterials for potentially further advancement in energy electrocatalysis. Then, we discuss the state-of-the-art characterizations and representative intermetallic electrocatalysts with emphasis on oxygen reduction reaction evaluated in a MEA setup. We summarize this review by laying out existing challenges and offering perspective on future research directions toward practicing intermetallic electrocatalysts for energy conversions.

Precise synthetic control of exclusive ligand effect boosts oxygen reduction catalysis.

Ligand effect, induced by charge transfer between catalytic surface and substrate in core/shell structure, was widely proved to benefit Pt-catalyzed oxygen reduction reaction by tuning the position of d-band center of Pt theoretically. However, ligand effect is always convoluted by strain effect in real core/shell nanostructure; therefore, it remains experimentally unknown whether and how much the ligand effect solely contributes electrocatalytic activity improvements. Herein, we report precise synthesis of a kind of Pd3Ru1/Pt core/shell nanoplates with exclusive ligand effect for oxygen reduction reaction. Layer-by-layer growth of Pt overlayers onto Pd3Ru1 nanoplates can guarantee no lattice mismatch between core and shell because the well-designed Pd3Ru1 has the same lattice parameters as Pt. Electron transfer, due to the exclusive ligand effect, from Pd3Ru1 to Pt leads to a downshift of d-band center of Pt. The optimal Pd3Ru1/Pt1-2L nanoplates achieve excellent activity and stability for oxygen reduction reaction in alkaline/acid electrolyte.

Single-Atom Cr-N4 Sites with High Oxophilicity Interfaced with Pt Atomic Clusters for Practical Alkaline Hydrogen Evolution Catalysis.

Although dispersing Pt atomic clusters (ACs) on a conducting support is a promising way to minimize the Pt amount required in hydrogen evolution reaction (HER), the catalytic mass activity and durability of Pt ACs are often unsatisfactory for alkaline HER due to their unfavorable water dissociation and challenges in stabilizing them against agglomeration and detachment. Herein, we report a class of single-atom Cr-N4 sites with high oxophilicity interfaced with Pt ACs on mesoporous carbon for achieving a highly active and stable alkaline HER in an anion-exchange-membrane water electrolyzer (AEMWE). The as-made catalyst achieves the highest reported Pt mass activity (37.6 times higher than commercial Pt/C) and outstanding operational stability. Experimental and theoretical studies elucidate that the formation of a unique Pt-Cr quasi-covalent bonding interaction at the interface of Cr-N4 sites and Pt ACs effectively suppresses the migration and thermal vibration of Pt atoms to stabilize Pt ACs and contributes to the greatly enhanced catalytic stability. Moreover, oxophilic Cr-N4 sites adjacent to Pt ACs with favorable adsorption of hydroxyl species facilitate nearly barrierless water dissociation and thus enhance the HER activity. An AEMWE using this catalyst (with only 50 µgPt cm-2) can operate stably at an industrial-level current density of 500 mA cm-2 at 1.8 V for >100 h with a small degradation rate of 90 µV h-1.

Fluorination of Covalent Organic Framework Reinforcing the Confinement of Pd Nanoclusters Enhances Hydrogen Peroxide Photosynthesis.

Metal-isolated clusters (MICs) physically confined on photoactive materials are of great interest in the field of photosynthesis of hydrogen peroxide (H2O2). Despite recent important endeavors, weak confinement of MICs in the reported photocatalytic systems leads to their low catalytic activity and stability. Herein, we report a new strategy of fluorinated covalent organic frameworks (COFs) to strongly confine Pd ICs for greatly boosting the photocatalytic activity and stability of H2O2 photosynthesis. Both experimental and theoretical results reveal that strong electronegative fluorine can increase the metal-support interaction and optimize the d-band center of Pd ICs, thus significantly enhancing the stability and activity of photocatalytic H2O2. An optimal TAPT-TFPA COFs@Pd ICs photocatalyst delivers a stable H2O2 yield rate of 2143 µmol h-1 g-1. Most importantly, the as-made TAPT-TFPA COFs@Pd ICs exhibit high catalytic stability over 100 h, which is the best among the reported materials.

Cooperative Rh-O5/Ni(Fe) Site for Efficient Biomass Upgrading Coupled with H2 Production.

Designing efficient and durable bifunctional catalysts for 5-hydroxymethylfurfural (HMF) oxidation reaction (HMFOR) and hydrogen evolution reaction (HER) is desirable for the co-production of biomass-upgraded chemicals and sustainable hydrogen, which is limited by the competitive adsorption of hydroxyl species (OHads) and HMF molecules. Here, we report a class of Rh-O5/Ni(Fe) atomic site on nanoporous mesh-type layered double hydroxides with atomic-scale cooperative adsorption centers for highly active and stable alkaline HMFOR and HER catalysis. A low cell voltage of 1.48 V is required to achieve 100 mA cm-2 in an integrated electrolysis system along with excellent stability (>100 h). Operando infrared and X-ray absorption spectroscopic probes unveil that HMF molecules are selectively adsorbed and activated over the single-atom Rh sites and oxidized by in situ-formed electrophilic OHads species on neighboring Ni sites. Theoretical studies further demonstrate that the strong d-d orbital coupling interactions between atomic-level Rh and surrounding Ni atoms in the special Rh-O5/Ni(Fe) structure can greatly facilitate surface electronic exchange-and-transfer capabilities with the adsorbates (OHads and HMF molecules) and intermediates for efficient HMFOR and HER. We also reveal that the Fe sites in Rh-O5/Ni(Fe) structure can promote the electrocatalytic stability of the catalyst. Our findings provide new insights into catalyst design for complex reactions involving competitive adsorptions of multiple intermediates.

Cu-Doped Heterointerfaced Ru/RuSe2 Nanosheets with Optimized H and H2 O Adsorption Boost Hydrogen Evolution Catalysis.

Ruthenium chalcogenide is a highly promising catalytic system as a Pt alternative for hydrogen evolution reaction (HER). However, well-studied ruthenium selenide (RuSe2 ) still exhibits sluggish HER kinetics in alkaline media due to the inappropriate adsorption strength of H and H2 O. Herein, xx report a new design of Cu-doped Ru/RuSe2 heterogeneous nanosheets (NSs) with optimized H and H2 O adsorption strength for highly efficient HER catalysis in alkaline media. Theoretical calculations reveal that the superior HER performance is attributed to a synergistic effect of the unique heterointerfaced structure and Cu doping, which not only optimizes the electronic structure with a suitable d-band center to suppress proton overbinding but also alleviates the energy barrier with enhanced H2 O adsorption. As a result, Cu-doped heterogeneous Ru/RuSe2 NSs exhibit a small overpotential of 23 mV at 10 mA cm-2 , a low Tafel slope of 58.5 mV dec-1 and a high turnover frequency (TOF) value of 0.88 s-1 at 100 mV for HER in alkaline media, which is among the best catalysts in noble metal-based electrocatalysts toward HER. The present Cu-doped Ru/RuSe2 NSs interface catalyst is very stable for HER by showing no activity decay after 5000-cycle potential sweeps. This work heralds that heterogeneous interface modulation opens up a new strategy for the designing of more efficient electrocatalysts.

Amorphous MoOx with High Oxophilicity Interfaced with PtMo Alloy Nanoparticles Boosts Anti-CO Hydrogen Electrocatalysis.

Advancing electrocatalysts for alkaline hydrogen oxidation/evolution reaction (HOR/HER) is essential for anion exchange membrane-based devices. The state-of-the-art Pt-based electrocatalysts for alkaline HOR suffer from low intrinsic activities and severe CO poisoning due to the challenge of simultaneously optimizing surface adsorption toward different adsorbates. Herein, this challenge is overcome by tuning an atomic MoOx layer with high oxophilicity onto PtMo nanoparticles (NPs) with optimized Had , OHad , and COad adsorption for boosting anti-CO-poisoning hydrogen-cycle electrocatalysis in alkaline media. For alkaline HOR, this catalyst exhibits high kinetics and an exchange current density of 3.19 mA µgPt -1 at 50 mV versus reversible hydrogen electrode and 0.83 mA cmPt -2 , 10.3- and 3.8-fold higher than those of commercial Pt/C, respectively. For alkaline HER, it achieves an unprecedented overpotential of 37 mV at 10 mA cm-2 . Experimental and theoretical studies show that the orchestrated electronic and oxophilic regulation of the PtMo/MoOx interface NPs simultaneously optimizes Had and OHad adsorption for boosting alkaline hydrogen electrocatalysis, whereas reactive oxygen from the amorphous MoOx atomic layer lowers the CO oxidation reaction barrier, leading to superior anti-poisoning ability even at 100 ppm CO.

Coordination Polymer Electrocatalysts Enable Efficient CO-to-Acetate Conversion.

Upgrading carbon dioxide/monoxide to multi-carbon C2+ products using renewable electricity offers one route to more sustainable fuel and chemical production. One of the most appealing products is acetate, the profitable electrosynthesis of which demands a catalyst with higher efficiency. Here, a coordination polymer (CP) catalyst is reported that consists of Cu(I) and benzimidazole units linked via Cu(I)-imidazole coordination bonds, which enables selective reduction of CO to acetate with a 61% Faradaic efficiency at -0.59 volts versus the reversible hydrogen electrode at a current density of 400 mA cm-2 in flow cells. The catalyst is integrated in a cation exchange membrane-based membrane electrode assembly that enables stable acetate electrosynthesis for 190 h, while achieving direct collection of concentrated acetate (3.3 molar) from the cathodic liquid stream, an average single-pass utilization of 50% toward CO-to-acetate conversion, and an average acetate full-cell energy efficiency of 15% at a current density of 250 mA cm-2 .

In situ characterisation for nanoscale structure-performance studies in electrocatalysis.

Recently, electrocatalytic reactions involving oxygen, nitrogen, water, and carbon dioxide have been developed to substitute conventional chemical processes, with the aim of producing clean energy, fuels and chemicals. A deepened understanding of catalyst structures, active sites and reaction mechanisms plays a critical role in improving the performance of these reactions. To this end, in situ/operando characterisations can be used to visualise the dynamic evolution of nanoscale materials and reaction intermediates under electrolysis conditions, thus enhancing our understanding of heterogeneous electrocatalytic reactions. In this review, we summarise the state-of-the-art in situ characterisation techniques used in electrocatalysis. We categorise them into three sections based on different working principles: microscopy, spectroscopy, and other characterisation techniques. The capacities and limits of the in situ characterisation techniques are discussed in each section to highlight the present-day horizons and guide further advances in the field, primarily aiming at the users of these techniques. Finally, we look at challenges and possible strategies for further development of in situ techniques.

Tuning Electronic Structure and Composition of FeNi Nanoalloys for Enhanced Oxygen Evolution Electrocatalysis via a General Synthesis Strategy.

Developing low-cost and efficient oxygen evolution electrocatalysts is key to decarbonization. A facile, surfactant-free, and gram-level biomass-assisted fast heating and cooling synthesis method is reported for synthesizing a series of carbon-encapsulated dense and uniform FeNi nanoalloys with a single-phase face-centered-cubic solid-solution crystalline structure and an average particle size of sub-5 nm. This method also enables precise control of both size and composition. Electrochemical measurements show that among Fex Ni(1- x ) nanoalloys, Fe0.5 Ni0.5 has the best performance. Density functional theory calculations support the experimental findings and reveal that the optimally positioned d-band center of O-covered Fe0.5 Ni0.5 renders a half-filled antibonding state, resulting in moderate binding energies of key reaction intermediates. By increasing the total metal content from 25 to 60 wt%, the 60% Fe0.5 Ni0.5 /40% C shows an extraordinarily low overpotential of 219 mV at 10 mA cm-2 with a small Tafel slope of 23.2 mV dec-1 for the oxygen evolution reaction, which are much lower than most other FeNi-based electrocatalysts and even the state-of-the-art RuO2 . It also shows robust durability in an alkaline environment for at least 50 h. The gram-level fast heating and cooling synthesis method is extendable to a wide range of binary, ternary, quaternary nanoalloys, as well as quinary and denary high-entropy-alloy nanoparticles.

Mechanistic Insights into OC-COH Coupling in CO2 Electroreduction on Fragmented Copper.

The carbon-carbon (C-C) bond formation is essential for the electroconversion of CO2 into high-energy-density C2+ products, and the precise coupling pathways remain controversial. Although recent computational investigations have proposed that the OC-COH coupling pathway is more favorable in specific reaction conditions than the well-known CO dimerization pathway, the experimental evidence is still lacking, partly due to the separated catalyst design and mechanistic/spectroscopic exploration. Here, we employ density functional theory calculations to show that on low-coordinated copper sites, the *CO bindings are strengthened, and the adsorbed *CO coupling with their hydrogenation species, *COH, receives precedence over CO dimerization. Experimentally, we construct a fragmented Cu catalyst with abundant low-coordinated sites, exhibiting a 77.8% Faradaic efficiency for C2+ products at 300 mA cm-2. With a suite of in situ spectroscopic studies, we capture an *OCCOH intermediate on the fragmented Cu surfaces, providing direct evidence to support the OC-COH coupling pathway. The mechanistic insights of this research elucidate how to design materials in favor of OC-COH coupling toward efficient C2+ production from CO2 reduction.

A General Synthetic Method for High-Entropy Alloy Subnanometer Ribbons.

High-entropy alloys (HEAs) are attracting intensive attention due to their broad compositional tunability and interesting catalytic properties. However, precisely shaping the HEAs into suprathin low-dimensional nanostructures for achieving diverse applications remains an enormous challenge owing to their intrinsic thermodynamic instability. Herein we propose a new and general low-temperature method for incorporating up to eight metallic elements into one single-phase subnanometer ribbon to achieve the thinnest HEA metal materials in the world. We experimentally demonstrate that synthetic processes for suprathin HEA subnanometer ribbons (SNRs) include (1) different metal atom nucleation via galvanic exchange reaction between different metal precursors and Ag nanowire template, (2) co-reduction of different metal precursors on nanowire template, and (3) the removal of the inner Ag core. Density functional theory (DFT) calculations reveal that the crystallization and stabilization of HEA SNRs strongly depend on the "highly dynamic" Ag from the template, and the crystallization levels of HEA subnanometer ribbons are closely correlated with the concentration of Pt and Pd. We demonstrate that the present synthetic method enables the flexible control of components and concentrations in HEAs SNRs for achieving a library of HEA SNRs and also superior electrocatalytic properties. The well-designed HEA SNRs show great improvement in catalyzing the oxygen reduction reaction of fuel cells and also high discharge capacity, low charge overpotential, and excellent durability for Li-O2 batteries. DFT calculations reveal the superior electrochemical performances are attributed to the strong reduction capability from high-concentration reductive elements in HEAs, while the other elements guarantee the site-to-site efficient electron transfer.