A Bifunctional CdS/MoO2/MoS2 Catalyst Enhances Photocatalytic H-2 Evolution and Pyruvic Acid Synthesis

The best use of photogenerated electrons and holes is crucial to boosting photocatalytic activity. Herein, a bifunctional dual-cocatalyst-modified photocatalyst is constructed based on CdS/MoO2/MoS2 hollow spheres for hydrogen evolution coupled with selective pyruvic acid (PA) production from lactic acid (LA) oxidation. MoS2 and MoO2 are simultaneously obtained from the conversion of CdMoO4 in one step. In a photocatalytic process, the MoS2 and MoO2 function as the reduction and oxidation centers on which photogenerated electrons and holes accumulate and are used for hydrogen evolution reaction (HER) and PA synthesis, respectively. By monitoring the intermediates, a two-step single-electron route for PA production is proposed, initiated by the cleavage of the alpha-C(sp(3))-H bond in the LA. The conversion of LA and the selectivity of PA can reach ca. 29 % and 95 % after a five-hour reaction, respectively.