Electrochemical CO2 reduction on Pd-based electrodes: from mechanism understanding to rational catalyst design

Abstract

Electrochemical CO₂ reduction reaction (CO₂RR) driven by clean electricity to obtain valuable chemicals is a feasible way to achieve carbon neutrality and is thus attracting increasing attention. Among different transition metal-based CO₂RR catalysts, Pd is the unique one because of its potential-dependent 2e⁻ reduction product distribution is tunable from formate to CO. Moreover, the interconversion between CO₂ and HCOOH can be achieved at equilibrium potential only on Pd surfaces. Considering these advantages, this review summarizes recent research progress on Pd-catalyzed CO₂RR in the past five years, including the new mechanistic understanding on Pd surfaces, and the rational design of Pd-based electrocatalysts. For mechanism studies, reaction pathways, adsorption configurations for the formate intermediate, and roles of adsorbed CO species are discussed. For catalyst discovery, both monometallic Pd and Pd-based catalysts with secondary metal and metalloid elements are overviewed. At the end, we put forward the possibility of utilizing Pd-based catalysts in electrolyzers to bridge the fundamental research and actual application of such catalysts.