Initiating highly efficient (Bi,Ce)2(O,S)3−x oxysulfide catalysts with rich oxygen vacancies for hydrogen evolution via adjusting valence band configuration

Abstract

The role of oxygen vacancies (V_O) in semiconductors' photocatalytic hydrogen evolution reaction (PHER) activities is challenging. In this study, BiCeOS with different V_O abundances and n(Ce³⁺/Ce⁴⁺) amounts prepared by adjusting the hydrazine amount was evaluated. The theoretical and experimental results indicated that V_O converts tetravalent cerium into trivalent cerium to maintain electrical neutrality by creating an electron donor level in the band gap of BiCeOS. Thus, BiCeOS with rich V_O and higher n(Ce³⁺/Ce⁴⁺) amounts exhibits higher visible light–excited photocurrent and easier photoinduced charge separation than those of BiCeOS with poor V_O and lower n(Ce³⁺/Ce⁴⁺) amounts. DFT calculations indicate that BiCeOS with rich V_O strongly interacts with water at a high adsorption energy of −0.968 eV to form a distorted water molecule. Therefore, the introduction of V_O on the surfaces with subsequently partial Ce⁴⁺-to-Ce³⁺ conversion remarkably yields BiCeOS catalysts with excellent visible light PHER activities.