Reverse Quantum Wells in Gradient-Doped CdS for Photocatalytic H2O2 Production

The photocatalytic O2 reduction to produce H2O2 offers significant environmental benefits. However, its efficiency is hindered by rapid charge recombination and sluggish catalytic kinetics in the catalyst. Traditional elemental doping has been employed to mitigate these issues, but its efficacy is limited as heteroatoms within the bulk often trap charge carriers. To address these challenges, we propose a gradient doping strategy. Unlike uniform doping, gradient doping introduces additional active sites on the catalyst surface. Our engineered gradient Mn-doped CdS photocatalyst demonstrated a remarkable H2O2 generation rate of 1874 μmol g−1 h−1, with an apparent quantum efficiency of 65.2% at 475 nm. The gradient distribution of Mn creates reverse quantum wells within the CdS matrix, which significantly enhances charge extraction from the bulk to the surface. The surface enrichment of Mn not only facilitates the adsorption and activation of O2 but also promotes the formation of the crucial *OOH intermediate, thereby accelerating H2O2 production.