Energy band modulating of NiO/BiOCl heterojunction with transition from type-II to S-scheme for enhancing photocatalytic CO2 reduction

The photo-driven CO2 reduction holds significant potential in facilitating carbon fuel conversion. However, the inefficiency of charge conversion severely limits its spractical applications. Herein, the charge transfer routeway was tailored in NiO/BiOCl-7 heterostructures via a transform from type-II to S-scheme for enhancing CO2 photoreduction to CO. Such S-scheme NiO/BiOCl-7 heterojunctions were prepared by pH-modulation to optimize the energy band structure of BiOCl and introduce abundant oxygen vacancies. Surprisingly, the S-scheme NiO/BiOCl-7 heterojunctions exhibited a significantly enhanced production of CO (78.11 μmol·g−1·h−1) with an impressive selectivity of 97.1 %, representing a remarkable 1.7- and 4.3-fold improvement in CO yield compared to the type-II NiO/BiOCl heterojunctions and pure BiOCl samples, respectively. The in-situ spectral experiments and DFT calculations reveal that the superior CO production can be attributed to a lower energy barrier for COOH* and a smoother potential energy surface of the S-scheme heterojunction with abundant oxygen vacancies. This meticulous strategy of energy band modulation sheds light on the deliberate customization of Bi-based heterostructures with favorable charge transfer for highly effecient photocatalysis.