Pd/g-C3N4 photocatalyst for hydrogen production: Role of experimental condition for Schottky barrier

•Pd modified structural and optical properties of g-C3N4.•Reduction treatment improved Pd/g-C3N4 activity but deactivated g-C3N4.•Terminal –NH2 on g-C3N4 formed hydrogen bonds and blocked electron conductivity.•Pd-N bond formation enhanced interfacial contact for efficient charge mobility. The changes in structural and optical properties of g-C3N4 and Pd/g-C3N4 following reduction treatment have affected the photocatalytic activity. Improved H2 rate was observed on reduced Pd/g-C3N4, but g-C3N4 experiences deterioration of photocatalytic activity after reduction. The rate of hydrogen production was reduced from Pd/g-C3N4/450 °C > Pd/g-C3N4/250 °C > Pd/g-C3N4 > g-C3N4 > g-C3N4/250 °C > g-C3N4/450 °C. Impregnation of Pd on g-C3N4 reduced the recombination of photogenerated electrons by extending the separation of the electron-hole pair. The in-situ DRIFTS analysis revealed a high number of terminal –NH2 formed during the H2 reduction of g-C3N4. A higher density of –NH2 terminal enhanced hydrogen bonds in g-C3N4 that lead to the blocking of electron conductivity. Efficient coordination of hydrogen atom spillover from Pd to the surrounding g-C3N4 enhanced the g-C3N4/Pd interfacial contact via Pd-N bond formation for improved charge mobility. In-situ photocatalytic hydrogen production using triethanolamine (TEOA) as a sacrificial agent showed the role of the hydroxyl group on TEOA to scavenge the photogenerated holes.