Heteroatom Dopants Promote Two-Electron O₂ Reduction for Photocatalytic Production of H₂ O₂ on Polymeric Carbon Nitride

Polymeric carbon nitride modified with selected heteroatom dopants was prepared and used as a model photocatalyst to identify and understand the key mechanisms required for efficient photoproduction of H₂ O₂ via selective oxygen reduction reaction (ORR). The photochemical production of H₂ O₂ was achieved at a millimolar level per hour under visible-light irradiation along with 100 % apparent quantum yield (in 360-450 nm region) and 96 % selectivity in an electrochemical system (0.1 V vs. RHE). Spectroscopic analysis in spatiotemporal resolution and theoretical calculations revealed that the synergistic association of alkali and sulfur dopants in the polymeric matrix promoted the interlayer charge separation and polarization of trapped electrons for preferable oxygen capture and reduction in ORR kinetics. This work highlights the key features that are responsible for controlling the photocatalytic activity and selectivity toward the two-electron ORR, which should be the basis of further development of solar H₂ O₂ production.