Pore-size-tunable M-ZnO catalyst for highly selective electrocatalytic reduction of CO2 to CO

Electrocatalytic reduction of carbon dioxide (CO 2 RR) into value-added products represents a promising strategy for carbon neutrality, although achieving high CO selectivity and long-term stability remains challenging. Herein, a series of three-dimensional ordered macroporous (3DOM) ZnO catalysts with tunable pore sizes were synthesized using PMMA templates and subsequently modified with different metal dopants to regulate their electronic structures. Systematic studies revealed that pore architecture strongly influences CO 2 adsorption, mass transport, charge transfer, and catalytic activity. Among the synthesized materials, 3DOM ZnO with a pore size of 600 nm exhibited the highest surface area, enhanced CO 2 adsorption capacity, reduced charge-transfer resistance, and a CO Faradaic efficiency of 90.5 % at −1.0 V versus RHE. Further electronic modulation through metal doping significantly improved catalytic performance. Notably, 3DOM Cu-ZnO (1:32) achieved a CO Faradaic efficiency of 95.6 % at −1.0 V and maintained stable operation for 24 h without noticeable activity loss. XPS and EPR analyses revealed charge redistribution and abundant oxygen vacancies after metal incorporation, while in situ FTIR measurements confirmed the formation of key CO 2 RR intermediates. The superior performance is attributed to the synergistic effects of optimized macroporous architecture, enhanced charge transfer, and electronically regulated active sites. This work provides an effective strategy for designing highly selective and stable ZnO-based electrocatalysts for CO 2 → CO conversion.