Zinc iron oxide-hydroxide electrocatalysts for CO2 reduction to syngas

Abstract Electrochemical reduction of CO 2 into syngas (CO/H 2 ) using renewable electricity is an emerging approach to achieve carbon neutrality. However, precise regulation of competing carbon dioxide reduction reaction (CO 2 RR) and hydrogen evolution reaction (HER) to tailor CO/H 2 ratios remains a formidable challenge. Here we prepared two different compositions of hetero-structures, such as ZnO/Zn(OH) 2 – Fe 2 O 3 and ZnO – Fe 2 O 3 , on carbon paper by electrodeposition, named as ZnFeO@CP-3 and ZnFeO@CP-4, and examined their electrocatalytic CO 2 RR 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 CO 2 RR 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/H 2 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.