Anchoring highly distributed Pt species over oxidized graphitic carbon nitride for photocatalytic hydrogen evolution: The effect of reducing agents

Abstract

Platinum (Pt) as a cocatalyst over graphitic carbon nitride (g-C3N4) is the main active site in the hydrogen evolution reaction (HER). Therefore, controlling the properties of Pt is significant to achieve a high H2 production yield in which the reduction step of the Pt precursor is an important factor. In this study, we prepared Pt-loaded chemically oxidized g-C3N4 photocatalysts for photocatalytic hydrogen evolution using different Pt deposition methods-chemical reduction with hydrazine, hydrogen reduction, and photoreduction. The hydrogen evolution rate of the chemically oxidized Pt/g-C3N4 photocatalysts prepared via hydrogen reduction (1152.8 µmol g-1h-1) was the highest compared to those prepared via chemical reduction (409.9 µmol g-1h-1) and photoreduction (583.7 µmol g-1h-1). The hydrogen reduction method with a fine reducing ability could achieve a uniform distribution of Pt nanoparticles anchored onto the chemically oxidized g-C3N4 nanosheets while maintaining homogeneity between the Pt precursor - reducing agent - g-C3N4. Furthermore, during hydrogen reduction, the greatest -C=O content and lowest concentrations of -COOH and -COH groups on the g-C3N4 surface resulted in an extremely high Pt2+/Pt0 ratio, a strong electronic Pt-g-C3N4 interaction, and the highest charge transfer efficiency, enhancing the hydrogen evolution rate.