▎ 摘　　要

The hydrogen evolution reaction (HER) is an emerging renewable energy source to derive clean, efficient, and high-energy-density hydrogen fuel from electrochemical water splitting mostly by using traditional noble-metal-based catalysts. However, their scarcity has led to the emergence of carbon-based materials which are exceptionally promising alternatives for the HER. Herein, graphene capsules-decorated boron-carbon-nitride sheets are developed by pyrolyzing a mixture of pyridine borane and custom-made GCs. The 3D hollow GCs effectively increase the surface area to supplement more exposed active sites for the hydrogen adsorption/desorption reaction. The carbon-rich ternary hybrid structure favors adjusting the electrical conductivity, which provides better HER catalytic performances (overpotential of 333 mV at 10 mA cm(-2)) in acidic conditions. The long-term stability for 24 h and the simplest designing technique propose an effective metal-free electrocatalyst for commercial applications in the renewable energy field.