Phase-Dependent Electrocatalytic CO₂ Reduction on Pd₃Bi Nanocrystals

Alloying is a general strategy for modulating the electronic structures of catalyst materials. Compared to more common solid–solution alloys, intermetallic alloys feature well-defined atomic arrangements and provide the unique platform for studying the structure-performance correlations. It is, unfortunately, synthetically challenging to prepare the nanostructures of intermetallic alloys for catalysis research. In this contribution, we prepare intermetallic Pd₃Bi nanocrystals of a uniform size via a facile solvothermal method. These nanocrystals can phase-transform into solid solution alloy via thermal annealing while retaining a similar composition and size. In 0.1 M KHCO₃ aqueous solution, the intermetallic Pd₃Bi can selectively reduce CO₂ to formate with high selectivity (≈100 %) and stability even at <-0.35 V versus reversible hydrogen electrode, whereas the solid solution alloy has limited formate selectivity of <60 %. Such unique phase-dependence is understood via theoretical simulations showing that the crystallographic ordering of Pd and Bi atoms within intermetallic alloys can suppress CO poisoning and enhance the *OCHO adsorption during electrochemical CO₂ reduction to formate.