CoP decorated 2D/2D red phosphorus/B doped g-C3N4 type II heterojunction for boosted pure water splitting activity via the two-electron pathway

Abstract

Photocatalytic pure water splitting to produce H₂ with a two-electron process is an effective and more kinetically favorable method to obtain clean energy. Herein, a CoP decorated 2D/2D red phosphorus/B doped g-C₃N₄ (CoP/RP/BCN) type II heterojunction is synthesized to realize photocatalytic pure water splitting via a two-electron process. The optimal ternary CoP/RP/BCN photocatalyst displays a prominent H₂ yield of 166.2 μmol h⁻¹ g⁻¹, which is 207.8-fold greater than that of g-C₃N₄. The deep insight into the photocatalytic mechanism of CoP/RP/BCN reveals that the improved photocatalytic efficiency is ascribed to the synergistic effect of extended light absorption, accelerated charge transfer, and increased active reaction sites due to the novel heterostructure RP/BCN and co-catalyst CoP loaded. The introduction of B facilitates the intrinsic charge excitation and increases the work function of the carbon nitride framework, promoting charge transfer and heterojunction formation. With a phosphorization reaction, RP nanosheets tightly combine with BCN to enhance the visible-light absorption and construct the 2D/2D type II heterojunction. The difference in the work function between RP and BCN leads to band bending in the interface of the heterojunction, which induces an opposite migration of electrons and holes to enhance electron–hole pair separation. Moreover, CoP reduces water adsorption energy and provides H₂ generation sites, facilitating the final step of pure water splitting to produce H₂. This work proposes a promising strategy to achieve highly effective photocatalytic pure water splitting without any sacrificial reagents.