Electrocatalytic CO2 and HCOOH interconversion on Pd-based catalysts

Electrochemical energy storage and conversion toward sustainable carbon neutrality cycle is of great interest in today's society. In this perspective, we highlight the interconversion between carbon dioxide and formic acid by means of electrocatalytic CO₂ reduction reaction (CO₂RR) and formic acid oxidation reaction (FAOR) as an effective way to achieve that goal. In line with the distinctive catalytic nature of Pd to reversibly drive both FAOR and CO₂RR, we first illustrate the intimate mechanistic relation between these two reversed reactions over Pd surfaces. Next, recent advances in developing Pd-based bifunctional catalysts and relevant optimization strategies are briefly summarized, including geometric structure engineering with preferential facet exposure, construction of crystallographic ordering intermetallic, electronic structure manipulation through metal or metalloid doping to fine tune the binding strength for active and poisoning intermediates. At the end, our viewpoints on the design principles at both microscopic and macroscopic scales are offered toward an efficient CO₂ and HCOOH interconversion loop.