WO_3 and W_2N nanowire arrays for photoelectrochemical hydrogen production

摘要

Tungsten oxide (WO_3) nanowire array samples were nitrided in a NH_3 atmosphere to get complete conversion to tungsten nitride (W_2N) nanowires. UV-vis absorption spectroscopy shows that the band gap of WO_3 reduced from 2.9 eV to 2.2 eV after nitridation to W_2N. Photoelectrochemical properties of both WO_3 and W_2N nanowire array electrodes were investigated. WO_3 nanowire arrays show maximum incident photon-to-current conversion efficiency of 85% at 370 nm at 1.2 V vs. SCE. The high quantum efficiency is attributed to the nanowire architecture which ensures efficient light absorption and charge transport. The nanowire arrays were stable even up to 8 h of continuous gas evolution. W_2N nanowire arrays showed good photoactivity even at moderate bias. However, the pure W_2N electrodes were unstable with respect to photocorrosion. The mixed phase W_2N-WO_3 nanowires showed improvement in stability compared to pure W_2N nanowire arrays.