CTPAB inherits the catalytic activity from their unary counterparts, and the B-center is found to be the most favorable site for OER (Figure ). Under light irradiation, the photogenerated holes can provide an external drive potential of 0.75 V which can overcome the overpotential and contribute to a negative ΔG value for all the elementary steps. The dual-site process of OER is also considered as a comparison. As shown in Figure , the ηOER of the dual-site process remains to be 0.65 V under light irradiation, indicating that OER in this path is unfavorable. As a result, the OER process will spontaneously proceed in a single-site process on 2D CTPAB under light irradiation.