Activating bulk light harvest and electron transfer by deeper K doping in g-C3N4 for highly enhanced photocatalytic H2O2 production

The incorporation of potassium (K) ions into polymerized carbon nitride has been experimentally proven to be an efficient strategy for enhancing photocatalytic performance. However, the diffusion doping in the traditional ionothermal post-treatment of pre-polymerized precursor results in only surface-level K doping. This limitation hinders the effective utilization of the incident light and photogenerated electrons in the deeper bulk, especially the mismatched zone between the depth of light absorption and carrier diffusion length. In this study, K dopants were successfully introduced into the deep bulk of carbon nitride while maintaining the integrity of heptazine skeleton structure by treating exfoliated nanosheets. Compared to the superficially doped counterpart, both experiments and theoretical calculations indicate the deeper K dopants not only activate the bulk light harvest and facilitate carrier separation, but also fabricate an efficient electron transfer bridge. This bridge is responsible for extracting the electrons to the surface, thus facilitating the O2 reduction reaction. Consequently, a 139-fold enhancement in the H2O2 production rate over pristine carbon nitride was achieved, surpassing the performance of most recently reported photocatalysts. This study would deepen the understanding of the role of bulk doping and stimulate the development of doping beyond the superficial zone.