Selective Electrocatalytic CO2 Reduction to CO on Solid Nickel-Nitrogen-Doped Carbon Catalysts

Abstract

Electrochemical reduction represents a potential solution for converting carbon dioxide into more valuable products. One application for the carbon dioxide reduction reaction (CO2RR) would be carbon monoxide production, which is a valuable fuel and chemical precursor. An important challenge for commercialization of this process has been finding inexpensive catalysts with a high selectivity to carbon monoxide production. The selectivity towards carbon monoxide production is limited both by the competing hydrogen evolution reaction and poisoning caused by strong binding of carbon monoxide[1-2]. Initial work on non-precious metal CO2RR catalysts was based on iron-based metal-nitrogen-carbon (MNC) catalysts that were originally developed for the oxygen reduction reaction but have also shown strong CO generation performance [1, 3-5]. In the present work a Nickel based MNC catalyst is shown to have higher CO-production rates and less CO-poisoning in comparison to the iron-based MNC catalysts. In order to make this comparison, a family of catalysts is synthesized by the polymerization of nitrogen precursors around a carbon support and metal precursor [1, 6-7]. Upon heat treatment at 900 °C and subsequent acid washes, a nitrogen-rich, metal-nitrogen-carbon matrix is synthesized. These catalysts are characterized physically and electrochemically. In this work the nickel-based MNC catalyst is shown to be a significant improvement over the Fe-based catalysts and other non-precious metal alternatives. Although the iron-based catalyst shows lower onset overpotential, the nickel-based catalyst has higher peak currents and a longer lifetime. In this work it is found that the higher current densities and longer lifetime are a result of increased resistance to CO-poisoning. Furthermore, the CO-poisoning allows in situ confirmation of active site quantification via carbon monoxide adsorption techniques. Ultimately, these findings allow optimization of MNC catalysts resulting in high performance non-precious metal catalysts for CO2RR.