Although considerable progress has been achieved by Cu nanoparticles for catalyzing CO 2 reduction reaction (CO2RR), Cu single atom catalysts (Cu SACs) are generally suffered from inferior performance to that of widely investigated Fe, Co, Ni SACs. This phenomenon mainly ascribes to the lack of effective geometry and electronic engineering of copper active center from an atomic level. Herein, highly exposed atomically dispersed Cu-N x ( x denotes Cu–N coordination number) sites anchored on 3D porous carbon matrix are successfully synthesized through facile one step thermal activation, and Cu-N 4 sites exhibit boosted activity and selectivity compared to its nearly inert Cu-N 3 counterparts. Aided by density functional theory (DFT) calculations, the edge-hosted Cu-N 4 moieties are revealed as key active sites for efficient CO generation via optimized local coordination environment and electronic properties, which strongly interact with *COOH intermediate and facilitate the desorption of *CO. As a result, Cu-N 4 catalyst achieves high CO Faradaic efficiency (FE CO ) of over 90% from −0.6 to −1.1 V vs . RHE with a maximum value of 98%, surpassing the previously reported Cu SACs for CO 2 -to-CO conversion. This work provides new insight into proper Cu SACs design and fundamental mechanism understanding to boost CO2RR.
Photo-Fenton degradation as a promising strategy for antibiotic wastewater treatment attracted extensive attention, while the unsatisfactory catalytic performance vitally limits its industrial application. Herein, we demonstrate that confining atomically dispersed Cu into C3N4 (Cu–C3N4) enables fast H2O2 activation and efficient separation of photogenerated electron–hole pairs, resulting in a dramatic improvement of the degradation efficiency of the Photo-Fenton reaction. Photo-Fenton degradation of ciprofloxacin (CIP) was close to 99% within 30 min over optimized Cu–C3N4, corresponding to a pseudo-first-order rate constant of ∼0.0978 min–1, almost 4.5 times higher than pure C3N4 counterpart. The electron paramagnetic resonance, quenching experiments, and X-ray absorption fine structure results reveal that the superior Photo-Fenton catalytic performance is attributed to a nonradical reaction pathway, where the H2O2 is activated by the formation of the O═Cu–N4═O intermediate. The advanced catalyst as well as the refreshing H2O2 activation mechanism are of profound significance for the materials design in the wastewater treatment field.
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