Thermal-Treatment-Induced Cu-Sn Core/Shell Nanowire Array Catalysts for Highly Efficient CO(2 )Electroreduction

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 degrees 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 degrees C followed by electroreduction re-organized the clusters into a SnxO/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).