Zinc iron oxide-hydroxide electrocatalysts for CO2 reduction to syngas

Electrochemical reduction of CO2 into syngas (CO/H2) using renewable electricity is an emerging approach to achieve carbon neutrality. However, precise regulation of competing carbon dioxide reduction reaction (CO2RR) and hydrogen evolution reaction (HER) to tailor CO/H2 ratios remains a formidable challenge. Here we prepared two different compositions of hetero-structures, such as ZnO/Zn(OH)2 – Fe2O3 and ZnO – Fe2O3, on carbon paper by electrodeposition, named as ZnFeO@CP-3 and ZnFeO@CP-4, and examined their electrocatalytic CO2RR ability to form syngas. The influence of applied potential on obtaining different compositions of Zn and Fe in the Zn-Fe-O electrocatalysts was investigated, and their subsequent impact on CO2RR performance was studied. We determined that higher deposition potential favored Zn-rich materials (ZnFeO@CP-4) and lower potentials favored greater incorporation of Fe in ZnFeO@CP-3. Among all electrodes, ZnFeO@CP-4 displayed an optimal performance, achieving a high syngas Faradaic efficiency (FE) of 98% with a CO/H2 ratio of 3.9:1 at -1 V vs. RHE. Apart from syngas formation, ZnFeO@CP-3 demonstrates high CO FE of 87% at -1.1 V vs. RHE. The high selectivity towards CO formation highlights the versatility of Zn-Fe mixed oxide-hydroxide systems, which can further be tuned for targeted syngas or CO production.