C, N-vacancies and Br dopant co-enhanced photocatalytic H2 evolution of g-C3N4 from water and simulated seawater splitting

Introducing defects and heteroatoms on carbon nitride (g-C3N4, CN) framework are effective ways to enhance its photocatalytic activity by regulating light absorption and charge carriers separation. Herein, a mechanochemical method was employed to synthesize Br-doped C, N-deficient CN (CNV-mCN-Br) via ball-milling of N-containing precursor and 6-Bromopyridine-3-carbaldehyde (BrPyCHO) followed by calcining. The ball-milling-evolved mechanical forces and BrPyCHO-derived HBr induced formation of C, N vacancies and C-Br bond in CNV-mCN-Br framework. The CNV-mCN-Br exhibited curled nanosheets morphology and separated electrons-holes distribution. The photocatalytic H2 evolution rates of 1 %Pt-loaded CNV-mCN-Br in distilled water and simulated seawater were 22.21 and 34.41 mmol g–1h−1, respectively with 10% triethanolamine. The corresponding apparent quantum yields were 25.87% and 40.08% at 420 nm. This work provides a facile technique to simultaneously introduce defect and heteroatom in CN for high-efficiency photocatalytic H2 evolution.