Adjustable anion and cation vacancies CoSe catalysts on improving activity in photoelectrochemistry and electrocatalysis

Vacancies have a significant impact on catalysts as crystal structure, band structure and surface active sites. The effect of anion and cation vacancies on the catalytic performance of CoSe was studied. Catalysts with cation Co vacancies, anion Se vacancies and anion cation double vacancies were obtained. The results show that the single Co vacancy CovSe will form many pores as the active sites in the lattice and the position of the conduction band greatly moves from 0.55 eV of CoSe to −0.46 eV. This significantly improves the electrocatalytic hydrogen evolution performance, with overpotential of 161 mV and Tafel slope of 58 mV/dec. As a comparison, the overpotential of CoSe is 401 mV (Tafel slope of 171 mV/dec). In addition, Co vacancies can also improve carrier mobility and separation efficiency, demonstrating excellent photocurrent of 11.82 mA/cm2 at 1.23 eV (RHE), with 5.91 % conversion efficiency. The overall performance of CoSev with individual Se anion vacancies is not as good as CovSe. This indicates that cationic vacancies have a greater impact on the catalyst. There was no significant improvement in the performance of the sample with double vacancies of anions and cations, indicating that the two vacancies may have offset each other.