Rational Fabrication of Fe3O4/Co3O4/Graphdiyne Tandem Heterojunction toward Optimized Photocatalytic Hydrogen Evolution

Graphdiyne (GDY) is a novel two‐dimensional material composed of sp and sp 2 hybridized carbon atoms. Herein, GDY nanosheets are prepared from tribromobenzene by a simple ball‐milling‐assisted reduction–elimination method and is introduced into Fe 3 O 4 colloidal spheres and Co 3 O 4 cubes by low‐temperature mixing to efficiently synthesize Fe 3 O 4 /Co 3 O 4 /GDY tandem heterojunction photocatalysts. The hydrogen evolution activity of the optimized catalyst is 4.02 mmol g −1 h −1 under visible light (λ ≥ 420 nm), which is 100.05, 10.05, and 3.65 times higher than that of Fe 3 O 4 (0.04 mmol g −1 h −1 ), Co 3 O 4 (0.40 mmol g −1 h −1 ), and GDY (1.10 mmol g −1 h −1 ), respectively. In addition, the Prussian blue analog (PBA)‐derived Co 3 O 4 improves the light‐harvesting efficiency and reaction kinetics. More importantly, the establishment of tandem heterojunctions prompts energy‐level alignment and optimizes charge multichannel transfer, which is the dominant factor for enhanced photocatalytic activity. Combined with time‐resolved photoluminescence spectra, valence band X‐Ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and density functional theory calculations, the possible mechanism of Fe 3 O 4 /Co 3 O 4 /GDY series heterojunction is proposed and elucidated. This work provides a new idea for the construction of tandem heterojunctions based on graphdiyne and PBA derivatives.