Junction of porous g-C3N4 with BiVO4 using Au as electron shuttle for cocatalyst-free robust photocatalytic hydrogen evolution

Z-scheme g-C₃N₄/Au/BiVO₄ photocatalyst has been prepared successfully by assembling gold nanoparticles on the interface of super-thin porous g-C₃N₄ and BiVO₄, which exhibits outstanding photocatalytic performance toward hydrogen evolution and durable stability in the absence of cocatalyst. The highest photocatalytic hydrogen production rate of g-C₃N₄/Au/BiVO₄ was about 410.0 μmol g⁻¹ h⁻¹, which largely beyond that obtained of g-C₃N₄/BiVO₄ (23.3 μmol g⁻¹ h⁻¹), Au/g-C₃N₄ (244.6 μmol g⁻¹ h⁻¹) and pristine g-C₃N₄ (2.2 μmol g⁻¹ h⁻¹). The optimal apparent quantum efficiency was counted to be 6.8% at λ = 420 nm and 1.1% at λ = 600 nm. Moreover, the photocatalytic property of g-C₃N₄/Au/BiVO₄ could remain unchanged almost with 50 h in 5 cycles. The improvement of photocatalytic H₂ yield is attributed to the result of rapid separation of photogenic carriers in space and surface plasmon resonance effect of Au nanoparticles. In combination of photoelectrochemical measurement, active species capture experiment and electron paramagnetic resonance spectra, the underlying mechanism was illuminated. The pathway of charge carrier migration between semiconductor photocatalysts could be changed to Z-system through Au as an electron intermediate, which could not only benefit to maintain outstanding redox capability but also help to accelerate photo-generated carrier separation, and thus improve the photocatalytic activity.