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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 (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. [ABSTRACT FROM AUTHOR]

Benefitting from the maximum atom utilization efficiency, special size quantum effects and tailored active sites, single‐atom catalysts (SACs) have been promising candidates for bifunctional catalysts toward water splitting. Besides, due to the unique structure and properties, some amorphous materials have been found to possess better performance than their crystalline counterparts in electrocatalytic water splitting. Herein, by combining the advantages of ruthenium (Ru) single atoms and amorphous substrates, amorphous molybdenum‐based oxide stabilized single‐atomic‐site Ru (Ru SAs‐MoO3−x/NF) catalysts are conceived as a self‐supported electrode. By virtue of the large surface area, enhanced intrinsic activity and fast reaction kinetics, the as‐prepared Ru SAs‐MoO3−x/NF electrode effectively drives both oxygen evolution reaction (209 mV @ 10 mA cm−2) and hydrogen evolution reaction (36 mV @ 10 mA cm−2) in alkaline media. Impressively, the assembled electrolyzer merely requires an ultralow cell voltage of 1.487 V to deliver the current density of 10 mA cm−2. Furthermore, such an electrode also exhibits a great application potential in alkaline seawater electrolysis, achieving a current density of 100 mA cm−2 at a low cell voltage of 1.759 V. In addition, Ru SAs‐MoO3−x/NF only has very small current density decay in the long‐term constant current water splitting test. [ABSTRACT FROM AUTHOR]

Electrocatalysis of the hydrogen evolution reaction (HER) is a vital and demanding, yet challenging, task to produce clean energy applications. Here, the RuRh2 bimetallene nanoring with rich structural defects is designed and successfully synthesized by a mixed‐solvent strategy, displaying ascendant HER performance with high mass activity at −0.05 and −0.07 V, separately higher than that of the commercial Pt catalyst. Also, it maintains steady hydrogen bubble evolution even after 30 000 potential cycles in acid media. Furthermore, the RuRh2 bimetallene nanoring shows an outstanding activity in both alkaline and neutral media, outperforming that of Pt catalysts and other reported HER catalysts. A combination of atomic‐scale structure observation and density functional theory calculations demonstrates that both the grain boundaries and symmetry breaking of RuRh2 bimetallene cannot only weaken the adsorption strength of atomic hydrogen, but also facilitate the transfer of electrons and the adsorption of reactants, further boosting the HER electrocatalytic performance in all pH values. [ABSTRACT FROM AUTHOR]

Interfacial engineering and defect modulation can provide abundant active sites for catalysts to further boost the catalysis process. In this work, we develop a strategy to grow multi‐heterogeneous cobalt phosphide (CoP) nanorods with rich interfaces and defects along the one‐dimensional (1D) nanostructure by dual incorporation of Fe and Ru (CoFeP@Ru). Such a catalyst exhibits high activity and stability towards the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), with overpotentials of only 38 mV in 0.5 M H2SO4 and 48 mV in 1.0 M KOH for HER, and an overpotential of 340 mV in 0.1 M KOH for OER at 10 mA cm−2. Finally, as the bifunctional catalyst, an alkali electrolyzer is assembled and delivers at a low cell voltage, with almost 100 % Faradaic efficiency. Our experimental results demonstrate that Fe incorporation can disturb or even break the periodic structure of cobalt phosphides, causing a redistribution of the electronic structure and electron density of activity sites, while Ru can significantly enhance the catalytic kinetics, as well as electrochemical and mechanical stability. [ABSTRACT FROM AUTHOR]

The development of hydrogen energy relies to a large extent on the electrocatalysts that are highly efficient and widely sourced. Although transition metal phosphides (TMPs) have made great achievements in reducing the overpotential of hydrogen evolution reaction (HER), improving oxygen evolution reaction (OER) performance that is relatively lagging in view of relatively large overpotentials and high kinetics energy barriers is yet to be achieved. Herein, we propose an extremely convenient and practical approach to prepare iron-doped cobalt phosphide nanoparticles (Fe–CoxP NPs) via a one-step method by introducing an iron element in the in situ synthesis of a metal–organic framework (ZIF-67) and then subjecting to a phosphate treatment. The as-obtained Fe–CoxP showed an excellent OER and acceptable HER activities. In particular, for OER, the optimized Fe-doped CoxP (Fe0.27Co0.73P) exhibits an ultra-low overpotential of 251 mV at a current density of 10 mA cm−2, a negligible electrocatalytic degradation after 3000 CV cycles, and time over 40 h-reliant current density stability. When employed as cathode and anode electrodes in water splitting, the current density of 10 mA cm−2 can be achieved at a potential of 1.68 V. Our facile synthetic strategy and innovative ideas are undoubtedly beneficial to the design and construction of advanced water-splitting electrocatalysts. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Co addition increases atomic vacancies of Pd 2 Ag twinned interface and forms oxygen vacancies on CoO x surface. • Synergistic effect of surface atomic vacancies and metal twinned interfaces of v-Pd 2 CoAg tunes its surface charge-density distribution electrocatalysts. • v-Pd 2 CoAg possesses remarkable high HER and ORR catalytic activity and stability. • Unsaturated metal sites for O or H activation are simultaneously produced, resulting in great increase in activity. Abstract The integration of different active sites into metallic catalysts, which may impart new properties and functionalities, is desirable yet challenging. Herein, a novel strategy is demonstrated to integrate atomic vacancies onto a twinned Pd 2 CoAg surface. This strategy shows that such integration is highly efficient for hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) catalysis at room temperature. We characterize the composition and structure of the twinned Pd 2 CoAg nanocrystals with vacancy (v-Pd 2 CoAg NCs) interfaces and it is shown that the Co addition not only increases the atomic vacancies of Pd 2 Ag twinned interface, but also leads to the formation of oxygen vacancies on the surface of CoO x. The synergistic effect of the surface atomic vacancies and metal twinned interfaces of v-Pd 2 CoAg NCs can tune the charge-density distribution on the surface of the electrocatalysts, and result in a 5 times increase in ORR mass activity than that of Pt/C at 0.9 V. This study provides a foundation for the rational design of 'active sites' for practical HER and ORR electrocatalysts. [ABSTRACT FROM AUTHOR]

The construction of a high efficiency and stable catalyst for use in electrochemical hydrogen generation has great significance for renewable energy technologies. Herein, we show for the first time that Ru decorated with NiCoP is an excellent hydrogen evolving catalyst in both acidic and alkaline conditions, close in performance to that of Pt/C. [ABSTRACT FROM AUTHOR]

Freestanding metal nanoclusters can tune, precisely and effectively, the Gibbs free energy (ΔGH) of atomic hydrogen on the surface of materials. This enables the enhancement of hydrogen evolution activity. In this paper, we report a study of freestanding Pd-Ru distorted icosahedral clusters (ico-clusters) with less than 600 atoms by using a simple one-pot synthesis method. This Pd-Ru ico-cluster can be used as an efficient electrocatalyst for the hydrogen evolution reaction (HER) in acidic water, which is a promising alternative to Pt. The experimental and theoretical results suggest that the face-centered cubic (fcc) freestanding Pd-Ru distorted ico-clusters with less than 600 atoms ensure increased active edges and distorted defect sites, which reduce the coordination number for the atoms on the catalyst surface. Furthermore, Ru is a more effective hydrogen dissociation source, whereas Pd has a better hydrogen storage function. Pd-Ru can tune the ΔGH of atomic hydrogen adsorbed on a catalyst and reach an optimal equilibrium state that improves the HER performance. Our studies represent a robust approach towards the development of freestanding Pd-Ru distorted ico-clusters and advanced catalysts with non-Pt content for HER and many other heterogeneous reactions. [ABSTRACT FROM AUTHOR]

Developing bifunctional catalysts for both the hydrogen evolution reaction (HER) and the oxygen reduction reaction (ORR) is crucial for obtaining hydrogen easily by water splitting to promote electrochemical energy conversion in fuel cells. In this paper, we report a facile approach for the synthesis of Pd nanoparticle assemblies (NPAs) with porous structure as catalysts for both the HER and the ORR with desirable electrocatalytic activities and long-term stability. For the HER, the porous Pd NPAs exhibit a low onset potential, a small Tafel slope of 30 mV dec-1, and an exceptionally low overpotential of about 80 mV at a current density of 100 mA cm-2, and these porous Pd NPAs maintain their catalytic activity for at least 1000 cyclic voltammetry (CV) cycles of durability in 0.5 m H2SO4. As for the ORR, the porous Pd NPAs offer a remarkable catalytic activity with a diffusion-limiting current density of 3.85 mA cm-2, a half-potential of 0.837 V, and an onset potential of 0.926 V at 1600 rpm with a scan rate of 5 mV s-1. This study enables the design of novel bifunctional electrocatalysts in the renewable energy field. [ABSTRACT FROM AUTHOR]

[Display omitted] • DFT calculation predicts the enhanced stability of metastable CuRu x NS structures. • CuRu x NSs with rich in-situ metastable interfaces are designed and constructed. • CuRu 8 NSs possess outstanding alkaline HER activity and stability over 130 h. • CuRu 8 NSs have nearly 100% Faradaic yield for HER, showing high HER selectivity. • The coupling effect of metastable metal and 2D metal phases is key to catalysis. Precisely tuning the geometric and phase structure of noble metal-based heterostructure nanomaterials has been an effective way to induce a metastable defect interface system for the fast hydrogen evolution reaction (HER) kinetics in alkaline media. However, the unstable defect nature of metastable materials hinders their practical applications. Herein, as demonstrated by the theoretical calculation, the optimal Gibbs free energy of adsorbed H 2 O (ΔG H2O) and water dissociation (ΔG B) can be created for five-fold twinned Ru on Cu NSs with metastable interfaces. Thus, we successfully design and construct an in-situ metastable interface in five-fold twinned Ru supported on vertically oriented Cu nanosheets (Cu NSs) (devoted as CuRu x NSs). Among them, CuRu 8 NSs display unprecedented overpotentials of 8 and 39 mV at 10 and 100 mA cm−2, respectively. Furthermore, CuRu 8 NSs also demonstrate high intrinsic mass activity of 77.528 A g−1 at an overpotential of 20 mV and a large exchange current density of 5.014 mA cm−2, with outstanding stability (almost no activity degradation for 130 h). These represent one of the best alkaline HER catalysts to date for Ru-based catalysts. Importantly, CuRu 8 NSs possess nearly 100% Faradaic yield, confirming the high selectivity toward hydrogen evolution reaction. Furthermore, the fine structural analysis evidences that the in-situ incorporated five-fold twinned Ru nanoparticles coupled electronically with Cu NSs not only avoid migration and aggregation of the metal particles, but also effectively promote the formation of heterostructure nanosheet arrays with abundant active sites, enhancing the alkaline hydrogen evolution kinetics. [ABSTRACT FROM AUTHOR]

The theoretical predictions confirm that the compatible integration of Co 2 C and Co is beneficial to boost the water splitting kinetics. Experimentally, the designed Co-Co 2 C/CC heterostructure possesses abundant active sites, favorable kinetics and excellent intrinsic activity, thus exhibiting superior catalytic performance toward OER and HER. Furthermore, the assembled electrolyzer presents the excellent efficiency toward water electrolysis and can be driven by a commercial solar cell. [Display omitted] • Theoretical predictions confirm that the compatible integration of Co 2 C and Co can boost the water splitting kinetics. • The purposely Co-Co 2 C/CC possesses abundant active sites, favorable kinetics and excellent intrinsic activity. • The Co-Co 2 C/CC electrode exhibits superior OER and HER performance. • The assembled alkaline electrolyzer can be driven by a commercial solar cell. Utilizing cobalt carbide (such as Co 2 C) as water electrolysis catalyst remains a significant challenge due to the high overpotentials during the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, in terms of theoretical predictions, we confirm that metallic Co exhibits HER catalytic selectivity, whereas Co 2 C has moderate binding energies for OER intermediates, thus boosting water splitting kinetics by the compatible integration. Experimentally, we present an interface engineering of Co nanoparticles and Co 2 C nanowires on carbon cloth (CC) resulting in a unique Co-Co 2 C/CC electrocatalyst. The resultant Co-Co 2 C/CC entails low overpotentials of only 261 mV for OER and 96 mV for HER at the current density of 10 mA cm−2, which are one of the highest activities yet reported for cobalt carbide-based materials. Moreover, the assembled electrolyzer can be driven by a solar cell. This work enlightens a novel avenue for the rational design of metal carbide-based highly efficient electrocatalysts. [ABSTRACT FROM AUTHOR]

An ultrathin and highly curved 2D FeCoNi trimetal-organic framework nanosheet with abundant oxygen vacancies and heterointerfaces is designed and created, and displays outstanding OER performance as a direct-MOF catalyst. [Display omitted] • Ultrathin (1.5 nm) FeCo 2 Ni-MOF-74 nanosheets with rich oxygen vacancies are designed and constructed. • As direct-MOF catalyst, it displays the highest alkaline-OER activity level for MOF catalysts. • It also shows superior stability, which can maintain stable even for over 100 h operation. • DFT calculation results demonstrate the accelerated OER kinetics of defect-rich FeCo 2 Ni-MOF-74. • This work is very significant to develop the high-efficiency direct-MOF catalysts for electrocatalysis. Engineering the 2D metal-organic framework (MOF) material can enrich the metal-unsaturated edges as active sites for catalysis, however, introducing multiple heterointerfaces and vacancy defects into 2D MOF and exploring their effects on electrocatalytic oxygen evolution reaction (OER) remain a major challenge. Here we construct ultrathin and highly curved 2D FeCoNi trimetal-organic framework nanosheets (FeCoNi-MOFs) with only approximately 1.5 nm thickness and abundant oxygen vacancies. The formed defect-rich FeCoNi-MOFs display outstanding OER performance with a much smaller overpotential of 254 mV at 10 mA cm−2 and remarkable stability for over 100 h in alkaline solutions. This is the highest OER activity level attained for direct-MOF catalysts. Theoretical analysis of FeCoNi MOFs with rich oxygen vacancies further suggests that the increased Fermi level with multiple heterointerfaces and the addition of oxygen vacancies co-facilitate the pre-oxidation of low-valence metals and the reconstruction/deprotonation of intermediate metal−OOH, thus enhancing electron transport efficiency. [ABSTRACT FROM AUTHOR]

Coupling between Nitrogen-Doped Carbon layer derived from the biomass material and FeNi 3 intermetallic compound allows the synthesized FeNi 3 @NC electrocatalyst to exhibit excellent oxygen evolution reaction and oxygen reduction reaction performances. • N-doped carbon coupled FeNi 3 intermetallic compound is constructed by a super facile route. • FeNi 3 @NC owns rich defects, multiple active centers, a strong synergistic effect. • Such features allow FeNi 3 @NC with superior OER & ORR catalytic activity in alkaline media. • It has an ultralow overpotential for OER and a high half-wave potential for ORR. • FeNi 3 @NC based Zn-air battery owns the peak power density of 139 mW/cm2 with high stability. Developing OER&ORR bifunctional electrocatalysts has great significance for promoting the green energy conversion and storage technologies. Herein, nitrogen doped carbon coupled FeNi 3 intermetallic compound (FeNi 3 @NC) is designed and constructed by a super facile route. Rich defects, multiple active centers and strong synergistic effect allow FeNi 3 @NC with superior OER&ORR performance in alkaline environments. It exhibits an ultralow overpotential (E over) of 277 mV at 10 mA/cm2 for OER, and a high half-wave potential (E 1/2) of 0.86 V for ORR which outperform commercial Pt/C electrocatalysts. As a result, the ΔE (ΔE = E over ,OER – E 1/2 ,ORR) value of 0.65 V largely surpasses Pt/C-IrO 2 noble metal benchmarks (ΔE = 0.73 V). Furthermore, density function theory calculations are performed to probe its electrocatalytic mechanism. As expected, the peak power density and energy density of FeNi 3 @NC based rechargeable Zn-air battery reaches 139 mW/cm2 at 234 mA/cm2 and 915 Wh kg−1 at 10 mA/cm2, respectively, with excellent stability. Our exploration provides a guideline for synthesis of advanced bifunctional electrocatalyst. [ABSTRACT FROM AUTHOR]

Oxygen vacancies (O vac) can improve electrocatalytic activities in the oxygen evolution reaction (OER) process but remain a great challenge. Herein, we report a facile two-step approach to synthesizing La-doped CoO x nanosheets (NSs) with abundant oxygen vacancies by a La-triggered effect. Profiting from enriched O vac and fast charge transfer, La-doped CoO x NSs deliver a remarkably high OER activity with a low overpotential of 353 mV at 10.0 mA cm−2 and a Tafel slope of 78.2 mV dec−1, surpassing those of initial CoO x , IrO 2 , and most reported non-noble metal based electrocatalysts. In addition, they also exhibit superior durability with only slight degradation after continuous operation of 35 h in a 0.1 M KOH solution. Undoubtedly, the results inspire the use of La into the oxygen vacancies to explore highly active catalysts for various applications. Image 1 • Adding La increases oxygen vacancies of metal oxides, and leads to the formation of rich surface defects. • Synergistic effect of oxygen vacancies and defect of La-CoO x nanosheets facilitates electrocatalysis. • La-CoO x nanosheets possess remarkable high OER catalytic activity and stability in ultralow concentration alkaline media. [ABSTRACT FROM AUTHOR]