Synergistic\nInteractions\nin a Heterobimetallic Ce(III)–Ni(II)\nDiimine Complex: Enhancing the Electrocatalytic Efficiency for CO<sub>2</sub> Reduction

In this study, we\npropose a practical approach for producing\na\nheterobimetallic Ni(II)–Ce(III) diimine complex from an extended\nsalen-type ligand (H<sub>2</sub>L) to serve as an electrocatalyst\nfor CO<sub>2</sub> reduction and demonstrate an outstanding overall\nefficiency of 99.6% of the cerium–nickel complex and integrate\nit into applicable cell assemblies. We optimize not only the catalyst,\nbut the operational conditions enabling successful CO<sub>2</sub> electrolysis\nover extended periods at different current densities. A comparison\nof electrochemical behavior in H-cell and zero-gap cell electrolyzers\nsuggests potential applications for industrial scale-up. In the H-cell\nelectrolyzer configuration, the most elevated efficiency in CO production\nwas achieved with a selectivity of 56.96% at −1.01 V vs RHE,\nwhile HCOO<sup>–</sup> formation exhibited a selectivity of\n32.24% at −1.11 V vs RHE. The highest TON was determined to\nbe 14657.0 for CO formation, followed by HCOO<sup>–</sup> with\na TON of 927.8 at −1.11 V vs RHE. In the zero-gap electrolyzer\nconfiguration, the most efficient setup toward CO production was identified\nat a current density (CD) of 75 mA cm<sup>–2</sup>, a flow\nrate of 10 mL min<sup>–1</sup>, operating at 60 °C and\nutilizing a low KOH concentration of 0.1 M to yield a maximum faradaic\nefficiency (FE<sub>CO</sub>) of 82.1% during 24 h of stable electrocatalysis.