A novel cobalt complex of bptd and cobalt lactate complex to synergistically enhance photocatalytic HER activity and stability on CdS nanorods

A heterocycle 2,5-bis(2-pyridyl)-1,3,4-thiadiazole (bptd) as a polydentate reacts with CoCl2∙6H2O and NiCl2·6H2O to form two novel monomeric complexes, [Co(bptd)2Cl2]∙4H2O (1) and [Ni(bptd)2Cl2]∙4H2O (2). The complex 1 can act as electron cocatalyst to improve the rate of hydrogen evolution of CdS NRs under visible light irradiation. After the introduction of cobalt lactate complex as a hole cocatalyst, this noble-metal-free system exhibited a hydrogen evolution rate of 1123 ​μmol ​h−1, which is 12.2 times higher than that of pure CdS NRs. This system could work for 50 ​h with a TON of 7490, and the average AQY is 17% at 420 ​nm. Based on the results of experiments, the synergistic effect of complex 1 and cobalt lactate complex is proved and a possible mechanism for hydrogen production is proposed. This work may provide a reference for remedying the defects of faster carrier recombination and photocorrosion of CdS in heterogeneous environment.