Enhancing catalytic formaldehyde oxidation on CuO–Ag2O nanowires for gas sensing and hydrogen evolution

Abstract

CuO–Ag₂O nanowires are fabricated directly on the surface of an AgCuZn alloy via a facile method, which feature a hierarchical composition of the two oxides. The course of these nanostructures grown on the AgCuZn alloy substrate involves copper and silver co-crystallizing into hetero–oxides with acceleration of the rate by sacrificial zinc. Further, the prepared CuO–Ag₂O nanowires display an improved electrocatalytic oxidation of formaldehyde to hydrogen and formate at room temperature. There is evidence showing that the mechanism of the electrocatalysis is a chemical-looping electro-oxidation of a high electroactivity intermediate Cu₈O species, which is produced by formaldehyde reducing CuO. This uncommon reactive structure provides a route to monitor gaseous formaldehyde at the ppb level and generates much more hydrogen than CuO microparticles. The gas sensor exhibits an ultrahigh sensitivity of 52.40 μA ppm⁻¹ cm⁻² with a detection limit of 20.94 ppb, as well as response and restoring times of 2–5 s and 4–6 s, respectively. Besides, the speed of hydrogen evolution is also studied in this work (ca. 70 mL min⁻¹ g⁻¹), which is more than three times greater, and via a cleaner way, compared with CuO. Here we report an alloyed oxide nanostructure fabrication which suggests a method of facilely obtaining high performance catalytic materials.