Spectroelectrochemical Study of CO₂ Reduction on TiO₂ Electrodes in Acetonitrile

Abstract

One of the main current goals of humanity is the CO 2 conversion into high energy compounds for facilitating both a diminution of the CO 2 atmospheric levels and the development of energy storage strategies. In many studies, TiO 2 has been successfully used as a photocatalyst for CO 2 reduction, but there is still a lack of understanding of its catalytic behavior. In this context, CO 2 reduction has been studied on nanoporous TiO 2 electrodes in acetonitrile media by means of (spectro) electrochemical methods (ATR-IR and UV−vis). Importantly, the onset of the cathodic Faradaic processes related with CO 2 reduction on TiO 2 electrodes is located at −0.81 V versus SHE, which is less negative than that observed for metal electrodes under similar conditions. UV−vis spectroelectrochemical results indicate that the electrocatalytic behavior of TiO 2 is related to the generation of oxygen vacancies and Ti 3+ sites at its surface and promoted by electrolytes with nonintercalating cations in agreement with recent results on WO 3 electrodes. ATR-IR spectroelectrochemical measurements allow for monitoring of the TiO 2 /solution interfacial state as reduction proceeds. Specifically, IR bands for carbon monoxide and carbonyl groups related with carbonate and oxalate are observed. Additionally, a chromatographic analysis shows CO and oxalate as main products. With controlled water addition (0.5 M), methanol and CO were found to be the main products. Based on these results, a mechanism for CO 2 reduction on TiO 2 electrodes is presented in which the regeneration of the TiO 2 surface by oxide electrodissolution/deposition is a critical step.

Molecular catalysis of CO2 reduction: recent advances and perspectives in electrochemical and light-driven processes with selected Fe, Ni and Co aza macrocyclic and polypyridine complexes

“…So far only TiO 2 , which complies with these requirements, has been employed as a top-cathode layer. Nevertheless, this metal oxide is electrochemically active, 171,172 and FE for CO 2 reduction is significantly below unity. Anchoring strategies also deserve special attention, especially regarding pH range stability.…”

Design of CuInS2 hollow nanostructures toward CO2 electroreduction

“…At all potentials that we have used, the peak intensity detected at 1,060-1,070 cm −1 increases obviously. As summarized in previous reports, such a peak can be assigned to the totally symmetric C-O stretching vibration, ν 1 (CO 3 2− ) [19,28]. In addition, the 1,060-1,070…”

(Photo)electrocatalytic Versus Heterogeneous Photocatalytic Carbon Dioxide Reduction

“…CO 2 reduction was also performed on TiO 2 electrodes immersed in acetonitrile and very small amounts of water [85,86] . Methanol, CO and oxalate ion were obtained as the most important products.…”