Controllable doping of nitrogen and tetravalent niobium affords yellow and black calcium niobate nanosheets for enhanced photocatalytic hydrogen evolution

Elemental doping and liquid exfoliation are two efficient approaches to improve the visible-light-driven photocatalytic activity of Nb/Ta based perovskite semiconductors. Herein, by liquid exfoliation of nitrogen and tetravalent niobium controllably doped KCa2Nb3O10 precursors, yellow and black [Ca2Nb3O10](-) nanosheets with single-molecule thickness were fabricated for the first time for hydrogen evolution under visible-light irradiation. Comparative experiments on the ammonization conditions revealed that the additive K2CO3 played an essential role in determining the reduction of Nb5+ through a defect chemistry mechanism. Due to the synergistic effect of N- and Nb4+-doping, black [Ca2Nb3O10](-) nanosheets exhibit superior visible-light-driven photocatalytic activity to yellow and bare [Ca2Nb3O10](-) nanosheets. These results can not only provide deeper insights into the contributions from N- and Nb4+-doping to wide-bandgap semiconductors, but also give examples combining two chemical manipulation approaches towards enhanced photocatalytic performance.