Self-assembled novel Co/Ni-based ε-Keggin crystal materials as highly efficient photocatalysts for diluted CO2 photoreduction

Abstract

The light-driven catalytic conversion of diluted CO₂ resources into value-added CO can be perceived as an effective way to fulfill sustainable green energy development, yet it's still in its inception stage because triggering this reaction remains a challenge due to its inert CO₂. Herein, two unprecedented polyoxometalate-based crystalline heterogeneous catalysts formulated as {[H₄GeMo₈^VMo₄^VIO₄₀Co₄][DETA]₄}·5H₂O (Co-ε-Keggin) and {[H₄GeMo₈^VMo₄^VIO₄₀Ni₄][DETA]₄}·4H₂O (Ni-ε-Keggin) (DETA = diethylenetriamine) were elaborately prepared. Remarkably, thanks to the Ni site's capacity to bind CO₂ and effective charge separation capability of Ni-ε-Keggin, it exhibits an ultra-high rate of 24 657.2 μmol g⁻¹ h⁻¹ with a high CO selectivity of 98.3% in a pure CO₂ atmosphere, and 16 199.3 μmol g⁻¹ h⁻¹ with 94.6% selectivity in 10% diluted CO₂. These results are superior to the performance of most photocatalysts in diluted CO₂ and also better than the behavior of many photocatalysts in pure CO₂ photocatalysis. The pioneering designs of Co/Ni-ε-Keggin series crystalline materials applied for low-concentration CO₂ open up a new platform for CO₂ efficient resource conversion.