Different behaviors on the external and inner surface of hollow CdS/VS-MoS2 heterojunctions in photoelectrocatalytic CO2 reduction via SH-assisted mechanism

The photoelectrocatalytic reduction of CO2 to value-added chemicals is a promising methodology to address both environmental and energy issues on the earth. Herein, a hollow heterojunction of CdS/VS-MoS2 rich in S-vacancies (VS) was designed, synthesized and applied to the photoelectrocatalytic reduction of CO2. The different selectivity for products between inner and external surfaces of hollow catalysts were carefully investigated. The selectivity for C2 chemicals on the inner surfaces is up to 67.0% due to the increased collision probability of the intermediates in the confined cavity. Therefore, the morphology is important to the selectivity of products in photoelectrocatalytic reduction of CO2. A new mechanism of SH-assisted CO2 reduction was proven by DFT calculation and the important active species such as *OCHO, *CO2−, SH (active hydrogen atom trapped by S atom) were verified obviously by the operando IR spectra on a self-installed instrument. [Display omitted] •CdS/VS-MoS2 heterojunctions were prepared for photoelectrocatalytic CO2 reduction.•N-n Heterojunctions and S-vacancies promote the separation efficiency of carriers.•The external and inner surface of hollow catalyst show different C2 selectivity.•The active hydrogen atoms are identified to be S-H showing δS−H in operando IR.•The mechanisms and intermediates are verified by DFT and operando IR, respectively.