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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]

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]

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]

Graphical abstract Highlights • Fe-N-S codoped carbon matrix/nanotube nanocomposite directly derived from a MOF precursor. • Fe-N-S codoped carbon matrix/nanotube nanocomposite exhibits a high half-wave potential of 0.91 V in alkaline condition. • Fe-N-S codoped carbon matrix/nanotube nanocomposite exhibits a half-wave potential of 0.78 V in acidic condition. Abstract MOF-derived carbon-based nanomaterials have attracted great attention due to the outstanding electrocatalytic performance, low-cost and super stability. To design an excellent catalyst, Fe, N and S codoped carbon matrix/carbon nanotube nanocomposites (Fe-N-S CNN) are prepared by pyrolysis of ZIF-8 impregnated with iron salt in this work. Benefiting from the synergistic effect of carbon matrix and nanotubes, abundant iron nitrides and thiophene-S active sites, the Fe-N-S CNN exhibits an excellent oxygen reduction reaction (ORR) performance with a half-wave potential of 0.91 V vs. RHE in alkaline conditions and 0.78 V vs. RHE in acidic conditions, while those of commercial Pt/C catalysts are 0.85 V vs. RHE and 0.795 V vs. RHE, respectively. Furthermore, Fe-N-S CNN as the cathode catalyst in a primary zinc-air battery shows a specific capacity of 700 mA h g−1. [ABSTRACT FROM AUTHOR]

• A covalent doping approach was employed to prepare ultrathin CoO nanosheets. • P 1 -CoO NSs rich with P–O bonds gave excellent alkaline OER activity and durability. • P 1 -CoO NS exhibits intrinsically high mass activity and large turnover frequency. • The ordered O vac and P-activation synergistically optimized the electronic states of CoO. A phosphorus-triggered synergy of ~1.0 nm ultrathin CoO nanosheets and O vacancy migration leads to high mass activity and turnover frequency for Co-based oxides toward the oxygen evolution reaction. [Display omitted] The surface configuration of low‐cost spinel oxides for oxygen evolution reaction (OER) can significantly affect the electrochemical behavior by generating a thin oxyhydroxide layer and other structures on the surface. Herein, we design and construct phosphorus (P)-activated ~1.0 nm ultrathin CoO nanosheets (devoted as P x -CoO NSs) with enriched P-O bonds and high valence state Co active sites, which is beneficial to the OER process due to the balance with Co3+ and oxygen vacancies on the reconstructed surface/interface. In addition, such an ultrathin nanosheet structure is also benefit to expose more active sites and improve the intrinsic electronic conductivity. As a result, the surface reconstructed P x -CoO NSs show superior OER activity compared with pure CoO and IrO 2 as benchmark. Furthermore, P 1 -CoO NSs demonstrate intrinsically high mass activity of 6.8 A g Co −1 at an overpotential of 270 mV, large turnover frequency of 0.0024 s−1 at an overpotential of 300 mV, and strong cycling stability in 0.1 M KOH solutions. Structural analysis further reveals that, as compared with CoO, the P-substitution not only induces the surface reconstruction into active Co oxyhydroxides under OER conditions, but also enhances the reaction kinetics. Undoubtedly, this work enriches the ways to prepare high-performance transition-metal-oxide-based catalyst for practical applications. [ABSTRACT FROM AUTHOR]