Low-overpotential full water splitting with metal-free self-supported electrodes obtained by amination of oxidised carbon cloth

Abstract

Low-cost, yet highly active hydrogen evolution and oxygen evolution electrocatalysts are crucial for effective high-scale hydrogen production by alkaline water electrolysis. In this work, we present a simple two-step technique for preparation of metal-free electrocatalytic electrodes tailored separately for hydrogen evolution and oxygen evolution electrodes. Both synthesis routes involve two steps of carbon cloth oxidation and following amination treatment. The choice of oxidation technique strongly affects the properties of obtained electrodes and thus the utility in hydrogen evolution and oxygen evolution reactions. The emphasis is on hydrogen evolution reaction which has rarely been performed using metal-free electrocatalysts in alkaline media. Herein, a low reaction overpotential of 325 mV (at a current density of 10 mA cm−2) was achieved by a free-standing electrode with abundant nitrogen and oxygen dopants. The activity of the nitrogen-doped electrodes correlated with the concentration of carbonyl groups on the electrode surface. On the other hand, sparingly N-doped carbon cloth has shown a high activity toward OER. In the case of both electrodes, good electron transfer is achieved thanks to direct modification of the carbon fibre surface with retention of high electric conduction of their bulk. The stable performance of both electrodes was presented in a model alkaline electrolyser with the materials used directly as a cathode and an anode.