DOI: https://doi.org/10.29363/nanoge.interect.2021.021
Publication date: 10th November 2021
The electrochemical reduction of carbon dioxide (CO2ER) offers a sustainable approach for CO2 reutilization and conversion into added value chemicals. A wide variety of products can be formed during CO2ER such as formate, CO, hydrocarbons and alcohols and therefore tuning the selectivity of CO2ER catalysts remains a major challenge in the field.
The initial reduction of CO2 (2e-) can yield formate or CO. While the former is commonly accepted as a terminal product which can’t be further reduced, CO has been demonstrated to be a key intermediate in the formation of higher reduction products ( >2e-) such as hydrocarbons and alcohols.[1] The CO2 and CO binding strength on the metal surface are key factors determining the selectivity.[2] Post transition metals like Sn, In, Ga have weak interaction with CO2 and are known to favor formate production.[3–5] Au and Ag that adsorb CO weakly release it as final product. Pt, Ni, Fe and Co that bind CO too strongly are poisoned and unable to further reduce it, suppressing CO2R and favoring HER. Cu stands out as the only metallic surface characterized by an intermediate CO binding strength that favors further reduction to hydrocarbons or alcohols. Bimetallic catalysts offer possible synergetic effects among different metals to yield optimal binding of CO as key intermediate and have been demonstrated as an approach for tuning selectivity in Cu based catalysts [6,7]
Here we present the screening of bimetallic composites as CO2ER electrocatalysts using a facile synthesis by spin coating of metal precursors in solution to form mixed oxides (MAMBOx) thin films. We focus on combining early transition metals traditionally known to bind CO strongly and favor HER (MA=Fe, Ni or Co) with post-transition metals (MB= In, Sn or Ga), known to suppress HER. The influence of metal composition on CO2ER selectivity will be discussed, along with the structural changes observed in the composites during in situ reduction