Oxygen-doped crystalline carbon nitride with greatly extended visible-light-responsive range for photocatalytic H2 generation

Crystalline carbon nitride (CCN) materials with photoresponse of more than 600 nm are rare. Here, we successfully prepared a series of oxygen doped K+ implanted CCN (KCN) with narrowed bandgap (2.71−1.62 eV) for the first time. Compared with most of the O-doped amorphous CN, the optical absorption can only reach 500 nm, and a few more than 500 nm, our oxygen doping strategy is adopted to activate more n→π* transitions to enhance visible light and even near-infrared light harvesting. This active-optimized O-doped KCN accounts for 45- and 10- times promotion than pristine CN and KCN in H2 generation under λ > 500 nm. Most importantly, its maximum active wavelength is up to 650 nm, which has obvious advantages than most CCN-based photocatalysts in the utilization of solar energy. This excellent solar capture and H2 production is attributed to the activated n→π* electron transition, and high crystallinity and conduction band (CB) position caused by oxygen doping.