• 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. ABSTRACT Nitrogen-doped carbon materials with a large specific surface area, high conductivity, and adjustable microstructures have many prospects for energy-related applications. This is especially true for N-doped nanocarbons used in the electrocatalytic oxygen reduction reaction (ORR) and supercapacitors. Here, we report a low-cost, environmentally friendly, large-scale mechano

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–2 in 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.