Assembling graphitic-carbon-nitride with cobalt-oxide-phosphate to construct an efficient hybrid photocatalyst for water splitting application

Abstract

A scalable method to load a cobalt-oxide-phosphate (CoPi) water oxidation electrocatalyst onto the surface of a mesoporous graphitic-carbon-nitride (mpg-CN_x) semiconductor is reported. This procedure resulted in significant enhancement of photocatalytic activity of the mpg-CN_x in water oxidation. The optimal loading gave an oxygen evolution rate of up to approximately 1 mmol O₂ g_cat⁻¹ h⁻¹ under 100 mW cm⁻² visible light illumination in a pH 7 phosphate buffer containing Ag⁺ or Na₂S₂O₈ as an electron scavenger which was 400 times faster compared with that of the untreated mpg-CN_x catalyst. Under visible light illumination and by employing a hole scavenger e.g. methanol, CoPi was converted into a H₂-CoCat HER electrocatalyst which significantly promoted the H₂ generation photocatalytic activities of mpg-CN_x. Without any electron/hole scavengers, the mpg-CN_x–CoPi–H₂-CoCat composite was able to catalyse the overall water splitting process.