Water splitting interfacial reaction kinetics and charge transport of four TiO₂- and ZnO-based nanostructures with similar thickness are investigated.

In this paper we present an easy, quick and scalable route, based on anodic oxidation, for the preparation of mesoporous SnO₂ as an efficient electrocatalyst for the CO₂ reduction reaction (CO₂RR). Crystallographically interconnected SnO₂ nanocrystals with abundant grain boundaries, high specific surface area and easily accessible porosity result to be active and selective for the CO₂RR. This electrocatalyst shows faradaic efficiency (FE) of about 95% at -0.97 V and -1.06 V vs. reversible hydrogen electrode (RHE) towards the formation of predominant HCOOH and minor CO. A peak FE value of 82 % for the HCOOH production is obtained at -1.06 V vs. RHE. High HCOOH partial current densities of 10.2 mA cm^-2 and 15.3 mA cm^-2 are observed at -0.97 V and -1.15 V vs. RHE, respectively. Thorough electrochemical characterizations demonstrate that the synthesized SnO₂-based gas diffusion electrode allows efficient diffusion of CO₂ even at high kinetics, due to the highly open porous structure. The good understanding of the catalyst behavior is achieved also after the electrode testing and it shows that the proposed preparation route results in a stable and durable material. The here reported promising results can be exploited for developing high-performance and sustainable electrocatalysts with a high potentiality to be implemented in real CO₂ conversion devices.