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Developing high-performance and cost-effective bifunctional electrocatalysts for water splitting is the key to large-scale hydrogen production. How to achieve higher performance with a lower amount of noble metal is still a major challenge. Herein, using a facile wet-chemistry strategy, we report the ultralow amount loading of ruthenium (Ru) on porous nickel foam (NF) as a highly efficient bifunctional electrocatalyst for water splitting. Theoretical simulations reveal that the coupling effect of Ru and Ni can significantly reduce the d-band center of the composite. The Ru-modified NF exhibits a very high level of HER activity with only 0.3 wt% of Ru, far surpassing commercial Pt/C. It only requires an extremely low overpotential (η10) of 10 mV to achieve a current density of 10 mA cm–2in alkaline solution and a quite low Tafel slope of 34 mV dec–1. This catalyst also shows remarkable performance for overall water splitting with a low voltage of 1.56 V at 10 mA cm–2. These findings indicate the potential of this material in water–alkali electrolyzers, providing a new approach for fabrication of low-cost advanced electrocatalysts.

Single-site metal atoms (SMAs) on supports are attracting extensive interest as new catalytic systems because of maximized atom utilization and superior performance. However, rational design of configuration-optimized SMAs with high activity from the perspectives of fundamental electron spin is highly challenging. Herein, N-coordinated Fe single atoms are successfully distributed over axial carbon micropores to form dangling-FeN4centers (d-FeN4). This unique d-FeN4demonstrates much higher intrinsic activity toward oxygen reduction reaction (ORR) in HClO4than FeN4without micropore underneath and commercial Pt/C. Both theoretical calculation and electronic structure characterization imply that d-FeN4endows central Fe with medium spin (t2g4eg1), which provides a spin channel for electron transition compared with FeN4with low spin. This leads to the facile formation of the singlet state of oxygen-containing species from triplet oxygen during the ORR, thus showing faster kinetics than FeN4. This work provides an in-depth understanding of spin tuning on SMAs for advanced energy catalysis.

Vanadium dopant into NiFe LDH nanosheets can not only favor mild self-reduction of Pt ions into clusters, but also boost the water-splitting kinetics of the resulting Pt/NiFeV LDH nanocomposites via regulating the interfacial electron redistribution. This work can spark inspiration of designing other bifunctional electrocatalysts toward efficient energy conversion and storage.

Hierarchical N-doped porous carbons (NPCs) with large surface area and controllable N-doping are synthesized by ball milling, followed by pyrolysis.As a Zn–air battery cathode, NPCs have comparable discharge performance to precious metal catalysts and more stability.NPCs also exhibit an excellent specific capacity and cycling stability when used as supercapacitor electrodes.