Thermal‐Treatment‐Induced Cu−Sn Core/Shell Nanowire Array Catalysts for Highly Efficient CO2 Electroreduction

Abstract Hierarchical Cu−Sn core/shell nanowire arrays were built on 3‐dimensional macroporous Ni foams through a two‐step deposition, annealing, and electroreduction treatment. Cu was electroplated on Ni foam substrates and the sample was annealed at 500 °C followed by electroreduction, producing Cu nanowires of 150 nm diameter in arrays on the skeleton of Ni foams. Sn nanoparticles of 14–80 nm were then chemically deposited on Cu nanowires in clusters and a second annealing treatment at 200 °C followed by electroreduction re‐organized the clusters into a Sn x O/Sn shell of 8 nm thickness. Creating such a Sn shell on Cu nanowires suppressed faradaic efficiencies for H 2 evolution from 55.7 to 10.1 % and for HCOOH formation from 13.2 to 2.0 % and enhanced CO generation from 32.0 to 90.0 % at an applied potential of −0.8 V (vs. RHE). The faradaic efficiency for CO production remained almost constant at 90.0–91.4 % with total current densities of −13.2 to −19.3 mA cm −2 between −0.8 and −1.2 V (vs. RHE).