Enhancing electron density of bulk g-C3N4 through phosphorus doping for promoting photocatalytic hydrogen evolution reaction

The polyphosphate cyanogen was used as phosphorus source to prepare phosphorus doped bulk g-C 3 N 4 with a coral-like hierarchical structure. Density functional theory calculations showed that phosphorus doping in bulk g-C 3 N 4 would lead to an increase of electron density, and the enriched electron density would enhance the separation and transfer of photon-generated carrier. For the sample of the phosphorus doped bulk g-C 3 N 4 20%, the photocatalytic hydrogen production rate reached 2.96 mmol g −1 h −1 , which is near 3 times of 1.01 mmol g −1 h −1 of the original bulk g-C 3 N 4 sample with 1% Pt loading under visible light. • In this contribution, polyphosphate cyanogen was used as phosphorus source to be doped in BCN to improve its photocatalytic hydrogen production. • The doping of phosphorus would tune BCN’s electronic structure and enrich its electron density, which resulting in the enhancement of separation and transfer of photon-generated carrier. • The faster separation and transfer of photoexcited electron-hole pair would promote the photocatalytic HER rates. • The BCN sample adding 20% polyphosphate cyanogen has the best photocatalytic hydrogen production. With 1% Pt loading, the photocatalytic hydrogen production rate reaches 2.96 mmol g −1 h −1 , which is 2.93 times of 1.01 mmol g −1 h −1 of the original BCN sample. • This work may inspire the further development of phosphorus doped g-C 3 N 4 (P-CN) for the harvesting and converting solar energy to hydrogen energy. Graphite-phase carbon nitride (g-C 3 N 4 ) has attracted extensive attention due the ubiquity of the raw materials, low price, and excellent visible light photocatalytic hydrogen evolution reaction (HER) activity. Bulk g-C 3 N 4 is more advantageous for industrial production and application compared with g-C 3 N 4 nanostructures such as nanosheets. Polyphosphate cyanogen was used herein as a phosphorus source to prepare phosphorus-doped bulk g-C 3 N 4 with a coral-like hierarchical structure. This structure affords more extensive contact between the photocatalyst and reaction medium, and is thus beneficial for the photocatalytic hydrogen evolution reaction (HER). Density functional theory calculations showed that phosphorus-doping in bulk g-C 3 N 4 can increase the electron density, thereby enhancing the separation and transfer of photon-generated carriers. The rate of the photocatalytic HER is thus promoted due to the faster separation and transfer of photoexcited electron-hole pairs. Bulk g-C 3 N 4 doped with 20% phosphorous afforded a photocatalytic hydrogen production rate of 2.96 mmol g −1 h −1 , which is ∼ 3 times higher than that of the original bulk g-C 3 N 4 sample with 1% Pt loading (1.01 mmol g −1 h −1 ) under visible light. This study may inspire the further development of phosphorus-doped g-C 3 N 4 for harvesting and converting solar energy to hydrogen energy.