Synergistic effect of Co(II)-hole and Pt-electron cocatalysts for enhanced photocatalytic hydrogen evolution performance of P-doped g-C3N4

g-C3N4 is a metal-free semiconductor and a potential candidate for photocatalytic H2 production, however, the drawbacks, rapid recombination rate and limited migration efficiency of photogenerated carriers, restrict its photocatalytic activity. Herein, Co(II) as a hole cocatalyst modified P-doped g-C3N4 were successfully prepared to ameliorate the separation efficiency of photoinduced carriers and enhance the photocatalytic hydrogen production. The photocatalytic results demonstrated that the P-doped g-C3N4 (PCN) exhibited higher photocatalytic activity compared with pure g-C3N4, while Co(II)/PCN photocatalyst exhibited further enhancement of photocatalytic performance. The proposed possible mechanism based on various characterizations is that P-doping can modulate the electronic structure of g-C3N4 to boost the separation of photogenerated-e− and h+; while the synergistic effect of both Co(II) (as hole cocatalyst) and Pt (as electron cocatalyst) can not only lead to the directional shunting of photogenerated e+-h− pairs, but further accelerate the photogenerated electrons transfer to Pt in order to join the photocatalytic reduction process for hydrogen evolution. As a result, the transportation and separation of photoinduced carriers were accelerated to greatest extent in the Pt/Co(II)/PCN photocatalyst.