Graphite carbon nitride-based metal-free bifunctional electrocatalysts for anion exchange membrane water electrolyzer

Abstract

Anion exchange membrane water electrolyzers (AEMWEs) are considered promising technologies that outperform alkaline water electrolyzers and proton-exchange membrane water electrolyzers due to their various advantages. In particular, one of the most important advantages of AEMWEs is that it does not have to use rare precious metal materials such as iridium and platinum as a catalyst. Therefore, for the commercialization and industrialization of AEMWE technology, basic research on cell performance using robust non-precious metal catalysts is urgently needed. Consequently, in this paper, metal-free electrocatalysts based on graphite carbon nitride were synthesized and nitrogen-doped carbon nanofiber was applied as a support. These materials exhibited oxygen evolution reaction (OER) activity comparable to the commercial NiFeO catalyst and demonstrated hydrogen evolution reaction (HER) activity, thereby substantiating its potential as a bifunctional catalyst. Furthermore, the application of the graphite carbon nitride to the anode of membrane electrode assemblies (MEAs) revealed outstanding performance with a current density of 389 mA cm⁻² at 1.9 V, and excellent durability within a full-cell system. Notably, by incorporating graphite carbon nitride at both the cathode and anode electrocatalyst, we have successfully achieved a current density of 272 mA cm⁻² at 1.9 V in a fully non-metal catalyst based AEMWE system. Such results will serve as a valuable source of inspiration for researchers in non-metal catalysts in electrolysis devices.