Towards highly-selective H2O2 photosynthesis: In-plane highly ordered carbon nitride nanorods with Ba atoms implantation

Graphitic carbon nitride (g-C3N4) shows great potential in photocatalytic H2O2 production. However, challenges arise from its low in-plane crystallinity and selectivity in two-electron oxygen reduction reaction (2e−-ORR), greatly limiting its H2O2 photosynthesis efficiency. Herein, we develop an ingenious strategy to simultaneously increase the in-plane crystallinity and induce the highly-selective 2e−-ORR by rationally designing barium (Ba) atom-implanted in-plane highly ordered g-C3N4 nanorods. The approach involves controllable synthesis of in-plane high crystallinity g-C3N4 nanorods with Ba implantation (BI-CN) using a BaCl2-mediated in-plane polymerization strategy. The unique Ba-N interaction induces the oriented polymerization of 3-s-triazine units to form well-arranged in-plane structures. Experimental and theoretical calculations clarify that the implanted Ba atoms function as positive charge centers, resulting in a Pauling-type O2 adsorption configuration. This minimizes O–O bond breaking energy, thus suppressing the four-electron oxygen reduction reaction (4e−-ORR) and facilitating a highly-selective 2e−-ORR pathway for efficient photocatalytic H2O2 production. Consequently, the optimized BI-CN3 photocatalyst exhibits an outstanding H2O2 production rate of as high as 353 μmol L−1 h−1, surpassing the pristine g-C3N4 by 6.1 times. This study concurrently optimizes the in-plane crystallinity and O2 adsorption sites of g-C3N4 photocatalysts for highly-selective H2O2 production, providing innovative insights for designing efficient photocatalysts with diverse applications.