Photoelectrocatalytic CO₂ Reduction to Formate Using a BiVO₄/ZIF-8 Heterojunction

Converting CO₂ into high-value chemical fuels through green photoelectrocatalytic reaction path is considered as a potential strategy to solve energy and environmental problems. In this work, BiVO₄/ZIF-8 heterojunctions are prepared by in-situ synthesis of ZIF-8 nanocrystals with unique pore structure on the surface of BiVO₄. The experimental results show that the silkworm pupa-like BiVO₄ is successfully combined with porous ZIF-8, and the introduction of ZIF-8 can provide more sites for CO₂ capture. The optimal composite ratio of 4 : 1-BiVO₄/ZIF-8 exhibits excellent CO₂ reduction activity and the lowest electrochemical transport resistance. In the electrocatalytic system, the formate Faraday efficiency of 4 : 1-BiVO₄/ZIF-8 at -1.0 V vs. RHE is 82.60 %. Furthermore, in the photoelectrocatalytic system, the Faraday efficiency increases to 91.24 % at -0.9 V vs. RHE, which is 10.8 times higher than the pristine BiVO₄. The results show that photoelectric synergism can not only reduce energy consumption, but also improve the Faraday efficiency of formate. In addition, the current density did not decrease during 34 h electrolysis, showing long-term stability. This work highlights the importance of the construction of heterojunction to improve the performance of photoelectrocatalytic CO₂ reduction.