The superior photocatalytic performance of H2O2 production over ZnxCd1-xS/HTCC photocatalyst and its application for C3H6 epoxidation via tandem reaction

Photocatalysis represents one of the green and low-cost pathways for producing high-value-added industrial products such as H 2 O 2 . However, the primary challenges facing this technology include low H 2 O 2 synthesis rates, susceptibility of H 2 O 2 to oxidation by holes, and prone decomposition of H 2 O 2 . Here, we propose a synergistic strategy combining oxygen reduction reaction (ORR) and water oxidation (WOR) to overcome the bottleneck of low H 2 O 2 synthesis rate by simultaneously driving efficient desorption of H 2 O 2 from the catalytic site, thus suppressing its oxidation and decomposition. Specifically, we first synthesized Zn-doped CdS (Zn x Cd 1-x S) via hydrothermal method. Hydrothermal carbonation carbon (HTCC) was then loaded onto the Zn x Cd 1-x S, forming a Zn x Cd 1-x S/HTCC heterojunction with a built-in electric field effect. Zn doping and the built-in electric field enhance the separation of photo-generated carriers, effectively ensuring the supply of electrons and holes required for the 2e − ORR and 4e − WOR. Concurrently, the abundant hydrogen atoms in HTCC enhance O 2 adsorption and activation, thereby promoting the 2e − ORR process. Furthermore, the Zn x Cd 1-x S/HTCC structure efficiently drives H 2 O 2 desorption, thereby suppressing H 2 O 2 decomposition dominated by hole-mediated mechanisms. In a pure water system, the photocatalytic H 2 O 2 production rate of Zn 0.08 Cd 0.92 S/HTCC (ZCS/HTCC) reached 2061 μmol g cat −1  h −1 . Moreover, the Zn x Cd 1-x S/HTCC can be combined with commercial titanium silicalite-1 to establish an effective tandem system by coupling photocatalytic in situ H 2 O 2 production and propylene epoxidation to produce epoxypropane (PO). A distinct (969 μmol g cat −1  h −1 ) and highly selective (>90%) production of PO was achieved using O 2 under visible light irradiation. It offers a novel strategy for not only utilizing solar energy, but also enabling the safe and green production of PO under mild natural condition.