Facet-Dependent Electrocatalytic Reduction of CO<sub>2</sub> to HCOOH over Pd Nanoparticles

Pd is one of the most promising catalysts for carbon dioxide electroreduction (CO 2 RR) to formate (HCOO-). However, the lack of understanding of the active phase remains remains obscure with the role of different crystal facets in the formation of formic acid. Herein, Pd nanocubes and nanooctahedra particles with Pd (100) and (111) facets were, respectively, prepared. Compared with ordinary Pd nanoparticles and Pd octahedra, Pd nanocubes exhibited the most excellent electrocatalytic performance of carbon dioxide reduction, achieving a Faraday efficiency of 96% for formate production at a low applied potential of-0.20 V (vs RHE) in 0.5 M KHCO 3 . At the same time, first-principles theoretical calculations also showed that the Pd (100) surface is more conducive to the conversion of CO 2 to HCOO* intermediates, thereby promoting the formation of formic acid. This result indicates that the Pd (100) crystal plane is more conducive to the reduction of CO 2 to formate. This research has important guiding significance for exploring the efficient reduction of carbon dioxide to formic acid catalyst.