Metal-Free Catalyst with Large Carbon Defects forEfficient Direct Overall Water Splitting in Air at Room Pressure

Hydrogen can be used as a conventional clean energy resource, only by obtaining it in a cheap, simple, and feasible way. From the perspective of solar energy utilization, photocatalytic water splitting is essentially limited by high electric energy and intermittent solar energy. Here, we demonstrate that the carbon defects could decompose water directly by using low-value mechanical energy in the daily environment without using the sacrificial agent. The prepared metal-free carbon catalyst (OPC-900) with rich graphene topological defects shows several redox states in acetonitrile, which can accumulate redox equivalents and respond for overall water splitting in air at room pressure. Under stirring or light conditions, charges can be created and accumulated on the catalyst surface and split water into H2 and O2 in low conductivity medium. The mechanical energy conversion efficiency of stirring in ultrapure water is 7.01%. Our work combines visible light with low-value mechanical energy for widespread decomposition of water to produce hydrogen in air under normal pressure.