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

Capture of CO 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 CO to formic acid (FA) over SnO monomers and dimers. Our density functional theory calculations infer a strong chemisorption of CO on SnO clusters forming a carbonate structure, whereas heterolytic cleavage of H provides a new pathway for the selective reduction of CO to formic acid at low overpotential. Among the two investigated pathways for reduction of CO 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 H and facilitates the formation of a formate intermediate, which determines the selectivity for FA over the alternative CO and H evolution reaction. It is confirmed that SnO clusters exhibit a different catalytic behaviour from their surface equivalents, thus offering promise for future work investigating the reduction of CO to FA via a hydride pinning pathway at low overpotential and CO capturing.