Ultrathin Z-scheme 2D/2D N-doped HTiNbO5 nanosheets/g-C3N4 porous composites for efficient photocatalytic degradation and H2 generation under visible light.

To realize highly efficient utilization of solar energy for solving problems of environmental pollution and energy shortage has attracted increasing attention. Herein, a two-step exfoliation-restacking process was employed to construct ultrathin Z-scheme two-dimensional (2D)/2D N-doped HTiNbO5 nanosheets/g-C3N4 (RTCN) heterojunction composites with the increased specific surface areas, showing the enhanced photocatalytic performance for rhodamine B (RhB) degradation and hydrogen (H2) generation under visible light irradiation. A 2D/2D heterojunction structure was formed between N-doped H+-restacked HTiNbO5 nanosheets (N-RTNS) and g-C3N4, which was beneficial for the effectively spatial separation of photogenerated charge carriers. The improved photocatalytic activities may be attributed to the synergistic effects of the increased specific surface area, N-doping and 2D/2D heterostructure. The active species of holes (h+), hydroxyl (•OH) and superoxide (•O2-) radicals contributed to RhB photodegradation. A Z-scheme photocatalytic mechanism was proposed over RTCN-2 composite, showing dual advantages of the highly redox ability and efficient charge carrier separation.