Hydride Pinning Pathway in the Hydrogenation of CO₂ to Formic Acid on Dimeric Tin Dioxide

Capture of CO₂ and its conversion into organic feedstocks are increasingly needed as society moves towards a renewable energy economy. Here, a hydride-assisted selective reduction pathway is proposed for the conversion of CO₂ to formic acid (FA) over SnO₂ monomers and dimers. Our density functional theory calculations infer a strong chemisorption of CO₂ on SnO₂ clusters forming a carbonate structure, whereas heterolytic cleavage of H₂ provides a new pathway for the selective reduction of CO₂ to formic acid at low overpotential. Among the two investigated pathways for reduction of CO₂ to HCOOH, the hydride pinning pathway is found promising with a unique selectivity for HCOOH. The negatively-charged hydride forms on the cluster during the dissociation of H₂ and facilitates the formation of a formate intermediate, which determines the selectivity for FA over the alternative CO and H₂ evolution reaction. It is confirmed that SnO₂ clusters exhibit a different catalytic behaviour from their surface equivalents, thus offering promise for future work investigating the reduction of CO₂ to FA via a hydride pinning pathway at low overpotential and CO₂ capturing.