Switching H₂O₂ production pathway from oxygen reduction to water oxidation via cyano groups modification: A dual-site mechanism on carbon nitride

The construction of a built-in electric field and precise modulation of active sites are pivotal for enhancing the efficiency of catalytic reactions, yet achieving synergistic enhancement through a simple modification remains a challenge. Herein, we report a facile NaSCN assisted thermal treatment strategy to graft cyano groups onto the terminal amino sites of g-C₃N₄ (CN). The introduced cyano groups not only enhance the intrinsic polarization of the material, as confirmed by a 1.83-fold increase in the dipole moment and a superior piezoelectric coefficient (d₃₃ = 67.2 pm/V), but also create a strong internal electric field that synergizes with the piezoelectric field to promote charge separation and transfer. Consequently, the optimized NHCN-3 catalyst achieves an outstanding piezo-photocatalytic H₂O₂ generation rate of 158.2 mM/g/h, which is 22.6 times greater than that of CN. Moreover, combined in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) and density functional theory (DFT calculations) indicate a dual-site reaction mechanism: the terminal carbon atom adjacent to the grafted cyano group in the modified material reduces the energy barrier for H₂O cleavage into the *OH intermediate, while the neighboring -NH- group promotes the reaction by adsorbing a hydrogen atom and transforming into -NH₂⁺ species. This research provides new ideas for the multi-site cooperative effect and regulation of the H₂O₂ reaction pathway, laying the foundation for the design of high-performance piezo-photocatalysts.