Ultra‐thin Pd and CuPd Bimetallic Alloy Nanosheets for Electrochemical Reduction of CO2

Abstract Pd is an attractive electrocatalyst for the conversion of CO 2 to CO. Herein, we report the synthesis of ultrathin Pd nanosheets with a (111) exposed facet which enables CO evolution to be achieved in a CO 2 saturated 0.1 m KHCO 3 solution in a conventional H‐cell with a faradaic efficiency of 74±4 % at −0.75 V vs RHE and a partial current density (calculated based on the geometric area) of −0.65 mA cm −2 . Further, to reduce the cost, Cu was introduced into the Pd nanosheets to form Cu x Pd y bimetallic alloy nanosheets with (111) exposed planes. The composition of the Cu x Pd y alloy played a significant role in determining the nature of the nanosheet structure and the product selectivity. When 50 % of the Pd was replaced by Cu, competitive CO evolution could still be achieved relative to use of purely Pd nanosheets with 57±5 % of CO achieved at −0.85 V vs RHE and a partial current density of −0.9 mA cm −2 . Under flow‐cell conditions with a higher CO 2 mass transport rate, CuPd nanosheets exhibited enhanced current densities in the range of −5 mA cm −2 to −35 mA cm −2 but with a negligible change in faradaic efficiencies irrespective of the applied potential in a 1.0 m KHCO 3 medium. The use of a 1.0 m KOH solution further improved the catalytic performance generating 71±3 % of CO with a partial current density of −58±2 mA cm −2 at a low potential of −0.6 V vs RHE. Post electrolysis characterization revealed structural transformations occurred during electrolysis that impacted the product selectivity of some catalysts.