The critical reason for the ineffectiveness of the metal electrocatalysts for aqueous CO₂ reduction is H₂ generation due to competitive proton (H⁺)/ water (H₂O) reduction. P-block based electrocatalysts are among the potential candidates for CO₂ reduction due to their high hydrogen overpotentials. Tin (Sn), Lead (Pb) and Indium (In) metal electrodes are well known electrocatalysts for CO₂ reduction to formate but little work has been done to engineer the surface structuring and analysis of the surface bound species. It is reported¹ that the presence of metastable oxides on the surface of metal catalyst accelerates the CO₂ conversion process by stabilizing the CO₂^•− intermediate on the nano-interface contrary to pure metallic interfaces. Taking inspiration from the fact that activity of a catalyst depends upon the active nano-interface under exquisite control of local conditions, herein we report the modification of Sn and Sn-Pb-Sb alloy catalysts for CO₂ conversion reaction. Thus in this study, we report the fabrication of oxide-derived (OD) Sn and multi−metallic alloy (Sn−Pb−Sb) electrodes which were prepared by electrochemical oxidation treatment at different potentials (4V, 5.5V, 7V and 9V vs. Ag/AgCl) in electrolyte of aqueous 0.3 M oxalic acid. We hypothesized that metastable oxides on multi-metallic nano-interfaces² would not only stabilize the CO₂^•− but would prefer C coordination of CO₂^•− with evolved grain boundaries. The phase structure, morphology, oxidation state, and electrochemical behaviour of the electrodes were probed systematically. The results demonstrate that pristine Sn electrodes show higher CO₂ conversion efficiency to formate (80% vs. 66%) compared to pristine Sn−Pb−Sb alloy electrode at −1.4 V vs. RHE. In contrast, the oxide derived alloy electrodes (OD−Sn−Pb−Sb) demonstrate higher CO₂ reduction activity and enhanced selectivity to formic acid (90% vs. 85%) when compared to pristine OD-Sn electrodes under identical conditions. The improved CO₂ reduction activity on preferentially grown OD-electrodes relative to the pristine metallic electrodes in both Sn and Sn−Pb−Sb alloy could be attributed to the presence of highly active sites on the grain boundary surfaces.

1. Y. Chen and M. W. Kanan, J. Am. Chem. Soc., 2012, 134, 1986-1989.

2. S. Rasul, D. H. Anjum, A. Jedidi, Y. Minenkov, L. Cavallo and K. Takanabe, Angew. Chem., 2015, 127, 2174-2178.