Photocatalytic splitting of water on g-C3N4-based single-atom Pt catalysts with stable “sandwich” structure: A combined first principles and semiempirical investigation

Solar-to-hydrogen energy conversion is a promising strategy to solve environmental pollution and energy crisis by utilizing photocatalytic water splitting. In this work, a “sandwich” structure of g-C3N4-based single-atom Pt catalyst for photocatalytic water splitting is proposed and investigated using a combined first principles and semiempirical study method. The calculation results indicate that, without any cocatalyst, the photogenerated holes in the valence band of BL-g-C3N4 cannot oxidize H2O to O2, and its OER performance is not better than that of the pristine monolayer g-C3N4. Significantly, the photogenerated holes in the valence band of the "sandwich" structured photocatalyst g-C3N4-Pt1-g-C3N4 can oxidize H2O to O2 without any cocatalyst. That is, the OER performance of g-C3N4-Pt1-g-C3N4 is better than that of the pristine g-C3N4 and the pristine BL-g-C3N4. However, it can be found that the introduction of single Pt atom confinement in the BL-g-C3N4 cannot effectively reduce HER energy barrier or improve the hydrogen evolution kinetics of BL-g-C3N4. In other words, the introduction of the confined single Pt atom in the BL-g-C3N4 not only fails to improve HER performance of BL-g-C3N4, but deteriorates HER catalytic performance of BL-g-C3N4. These findings provide some theoretical insights for engineers to prepare photocatalysts with higher activity and stability.