Enhancing visible light absorption for efficient CO reduction with black carbon nitride hollow microspheres

Pristine carbon nitride (PCN) suffers from poor absorption of light above 460 nm and rapid recombination of photo-induced charge carriers. We report a unique type of black carbon nitride hollow microspheres (3D-BCN) with nitrogen defects, which have larger specific surface area (106.3 m 2 g −1 vs. 6.5 m 2 g −1 ) and stronger solar absorption (200-1000 nm), narrower bandgap (1.63 eV), slower recombination of excitons, higher photo-generated current (1063 nA vs. 218 nA) and more efficient CO 2 reduction to CO (6.8 times as compared to PCN). Black carbon nitride hollow microspheres with nitrogen defects have excellent solar absorption capability, narrower bandgap, and much more efficient CO 2 photo-reduction.