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

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 mA 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.