Enhanced photocatalytic H2O2 yield by single-atom Pt decorated carbon nitride sheets via boosting *OOH intermediate generation.

Abstract

Producing H2O2 via photocatalytic oxygen reduction reaction (ORR) is a sustainable and promising method compared with the energy-consuming, waste-intensive, and indirect anthraquinone process and direct H2/O2 synthesis process. The high recombination effectivity of photogenerated electrons and holes, and the high energy hurdles required for generating the key *OOH intermediates greatly restrict the yield of H2O2. Here, a novel Pt-SA/g-C3N4 photocatalyst consisting of single-atom Pt anchored on g-C3N4 sheets is prepared by a molecular self-assembly strategy. The Pt-SA/g-C3N4 sheets exhibit an unexpectedly high H2O2 generation rate of 836 μmol·L−1·h−1, which is 3.0 times than that of g-C3N4 sheets and 10 times of bulk g-C3N4. Results indicate that single-atom Pt can accelerate the dissociation of excitons on g-C3N4 sheets, promoting the separation and transfer of electrons and holes. As a result, the formation of 1O2 and O2•− was promoted, which can facilitate the formation of key intermediate *OOH. Moreover, we deposited Pt-SA/g-C3N4 photocatalyst on a SERS-active 120 nm Au core for detecting and tracking the intermediate species during ORR process. The in situ SERS results provide direct spectroscopic evidence of chemisorbed OOH on the Pt single atom. DFT calculation results further confirm that single-atom Pt can suppress the O-O bond cleavage of the intermediate *OOH, whiCch can promote its further transformation to H2O2. This research offers profound insights into the ORR catalytic mechanism and the design of high-performance single-atom photocatalysts aimed at H2O2 production.