A facile synthesis of Br-modified g-C3N4 semiconductors for photoredox water splitting

Hydrogen production by semiconductor photocatalysis using abundant sunlight and water is an ideal method to address the globe energy and environment issues. Here, we present a facile synthesis of bromine doped graphitic carbon nitride (g-C3N4) photocatalysts for hydrogen evolution with visible light irradiation. Bromine modification is shown to enhance the optical, conductive and photocatalytic properties of g-C3N4, while still keeping the poly-tri-s(triazine) core structure as the main building blocks of the materials. This modification method can be generally applicable to several precursors of g-C3N4, including urea, dicyandiamide, ammonium thiocyanide, and thiourea. The optimal sample CNU-Br0.1 shows more than two times higher H2 evolution rates than pure CNU sample under visible light irradiation, with high stability during the prolonged photocatalytic operation. Results also found that the photocatalytic O2 evolution activity of CNU-Br0.1 was promoted when the sample was subjected to surface kinetic promotion by loading with cobalt oxide as a cocatalyst. This study affords us a feasible modification pathway to rationally design and synthesize g-C3N4 based photocatalysts for a variety of advanced applications, including CO2 photofixation, organic photosynthesis and environmental remediation.