Effect of hydrogen sources toward the CO2 photoreduction on boron decorated crystalline carbon nitride

Photocatalytic CO2 conversion to industrial fuels is considered an effective measure to solve energy and environmental problems. Presently, Catalysts for CO2 reduction reaction (CO2RR) are mostly confined to metal-based materials, but non-metal materials are less explored. We decorate the highly crystalline carbon nitride, i.e., poly (triazine) imides (PTI), with non-metallic boron (B) to obtain two B/PTI catalysts: Bi/PTI with B being deposited into the six-fold cavity of the PTI, and Bs/PTI with B substituting for C in PTI. For CO2RR, Bi/PTI follows a quasi Mars-van Krevelen process, but the high exposure of Bi results in an overly strong interaction with intermediates, inhibiting the reactivity. In contrast, Bs/PTI enhances the binding with intermediates by introducing Lewis acidbase pairs (B-N), which reduce the ring conjugation effect and induce the enrichment of electrons at the pyridine N. Hence, CO2 reduction with the adsorbed H* (Ha) hydrogenation mechanism in Bs/PTI has a significant reactivity.