Composition sensitive selectivity and activity of electrochemical carbon dioxide reduction on Pd–Cu solid-solution alloy nanoparticles

Abstract

The effect of alloying on the electrochemical carbon dioxide reduction reaction (CO₂RR) has been investigated to improve the electrocatalytic performance. Pd–Cu bimetallic alloys show high selectivity for formate and CO as CO₂RR products. However, the dependence of selectivity and activity on the alloy composition and applied potential is unclear. This study investigates the CO₂RR properties of Pd–Cu solid-solution bimetallic alloy nanoparticles (NPs) and discusses the effects of composition and potential for formate and CO generation. Composition-controlled Pd_xCu_100−x (x = 73, 64, 56, and 46) NPs are synthesized via alcohol reduction. Microstructural and composition analyses reveal that all alloy NPs have a well-controlled composition with solid-solution alloy structures, which are suitable for discussing the composition effect. The Pd_xCu_100−x NPs exhibit enhanced selectivity for formate irrespective of the alloy composition. Notably, the Pd₆₄Cu₃₆ presents a selectivity of over 50% for formate in the broadest range of potential regions (−0.55 to −1.05 V). In comparison, the highest selectivity of 82% is achieved for a slightly Pd-richer one (Pd₇₃Cu₃₇) only at −0.55 V. Suitable alloy compositions and applied potentials for formate generation differ in selectivity and activity (partial current density). On the other hand, CO generation increases with increasing Cu content, and the Pd₄₄Cu₅₆ shows the highest selectivity and activity. In contrast to formate, the potential window for CO generation is relatively wide. The results demonstrate that the precise tuning of the alloy composition and applied potential is crucial for maximizing CO₂RR properties of bimetallic alloy NPs catalysts.