Black nanostructured Nb2O5 with improved solar absorption and enhanced photoelectrochemical water splitting

Black TiO2, with increased solar light absorption and enhanced photocatalytic and photoelectrochemical (PEC) performance, has attracted enormous attention, stimulating us to explore the blackening of other oxide semiconductors for enhanced properties. Here, we report the fabrication of black nanostructured Nb2O5 and its enhanced PEC properties for the first time. We successfully prepared oxygen-deficient black Nb2O5 nanochannels, which contain a considerable amount of oxygen vacancies (Nb4+ sites) serving as shallow donors. Black Nb2O5 exhibits strong visible and infrared light absorption, which can absorb 75.5% solar energy, which is superior to 5.7% for pristine Nb2O5. The PEC performance of black Nb2O5 photoanodes is significantly enhanced with a relatively large photocurrent of 1.02 mA cm(-2) and a high applied bias photon-to-current efficiency (ABPE) of 0.345%, in comparison with the poor performance of pristine Nb2O5 (0.084 mA cm(-2) photocurrent and 0.056% ABPE). These results indicate that black Nb2O5 is a promising material for PEC application and solar energy utilization.