Band alignment of homojunction by anchoring CN quantum dots on g-C3N4 (0D/2D) enhance photocatalytic hydrogen peroxide evolution

Polymeric carbon nitride (C3N4) is a very attractive candidate to produce photocatalytic hydrogen peroxide (H2O2) due to its low-cost, metal-free characteristics. However, the low efficiency would limit its development to higher yields because of insufficient light absorption and electron-hole separation. Here, we developed a simple method to anchor CN quantum dots (QDs) onto g-C3N4 nanosheets to form a homojunction structure (HJ-C3N4), which could improve photocatalytic performance largely without introducing metal elements. Its superior efficiency is a result of the band alignment by the homojunction structure providing excellent electron-hole separation and QDs providing suppressed recombination. Simultaneously, the light responsiveness of QDs endows a wide spectrum-responsive adsorption and enhances the adsorption intensity. The H2O2 yield of the HJ-C3N4 reached 115 μmol L−1 h−1 in pure water by visible light, which has an 8.6x higher production than g-C3N4 nanosheets. The material design of 0D/2D homojunction could be extended to other materials with specific band alignment. [Display omitted] •Homojunction structure via 0D/2D configuration exhibits an excellent e−-h+ separation ability.•Type-I band in CN system promotes the full use of wide-spectrum absorption extending the absorption edge to nearly 600 nm.•In pure water by visible light (λ > 400 nm), H2O2 yield increases by 8.6 times reaching 115 μmol L−1 h−1.•The defect energy levels contributed by oxygen-terminal functional groups in QDs can suppress the carriers recombination.