Unraveling Precise Locations of Indium Atoms in g‐C3N4 for Ameliorating Hydrogen Peroxide Piezo‐Photogeneration

Increasing active sites in catalysts is of utmost importance for catalytic processes. In this regime, single‐atom dispersing on graphitic carbon nitrides (g‐C3N4) to produce fine chemicals, such as hydrogen peroxide (H2O2), is of current interest due to not only enhancing catalytic performance but also reducing the loading of necessary metals. Herein, g‐C3N4 is engineered by atomically dispersing aluminum (Al) or indium (In) sites to provide catalytic active centers via one‐step thermal shock polymerization. The addition of Al and In sites can accelerate the catalytic efficacy owing to the Lewis acid–base interactions between these metals and oxygen (O2). Under catalytic conditions, the formation of oxygenic radicals will strongly be associated with the enhanced formation of H2O2, confirmed by in situ electron paramagnetic resonance spectroscopy. Furthermore, the empirical analyses from positron annihilation spectroscopy show that In atoms will occupy the near positions of carbon vacancies (VC) to form NVC@InO bonds. This replacement will produce the highest formation energy based on the density functional theory calculations, improving the stability of atom‐dispersive materials. Therefore, via the combination of experimental and theoretical proofs, this study suggests the exact location of In atoms in g‐C3N4 structures, which can help boost the catalytic production of H2O2. This study depicts the unique structures of In single‐atom sites in g‐C3N4 for enhanced piezo‐photocatalytic oxygen reduction via improving Lewis acid–base interactions. The work also recognizes the possible reasons for catalytic degradation as the In active sites are converted to different In species under highly oxidative conditions, thus, enriching the understanding of catalytic deterioration over g‐C3N4‐supported single‐atom catalysts.