Retracted Article: Synthesis of Fe³⁺-incorporated open-framework gallium borate catalyst for photocatalytic CO₂ reduction driven by visible light irradiation

Abstract

Gallium borates semiconductors have been developed as effective photocatalysts for water splitting driven by UV light irradiation, but there is no relevant study for the CO₂ photoreduction application. Herein, we report the first systematic investigation of open-framework gallium borate—Ga₉B₁₈O₃₃(OH)₁₅•H₃B₃O₆•H₃BO₃ (Ga-PKU-1) applying to photocatalytic CO₂ reduction under visible light irradiation by doping Fe³⁺ ion doping onto the framework. Using hydrothermal method, a series of Fe³⁺-incorporated Ga-PKU-1 have been successfully obtained, and a high Fe³⁺-to-Ga³⁺ substitution content (~10 atom %) can be achieved. The Ga-PKU-1:xFe³⁺ (x = 0.02 ~ 0.10) photocatalysts are characterized completely by diverse tests (e.g., XRD, XPS, UV-Vis DRS, SEM, N₂ sorption). The effective replacement of Ga³⁺ ion by Fe³⁺ ion could inhibit the degree of crystallinity of Ga-PKU-1, and also significantly expands the scope of spectral response from UV light to visible light. Compared with bare Ga-PKU-1, Ga-PKU-1:0.10Fe³⁺ exhibits remarkable CO formation rate of 3.2 μmol/h/g at 30 °C, and the selectivity for CO evolution exceeds 91.4 %. Besides, the CO formation rate increases to 8.3 μmol/h/g after thes loading of Ag as the co-catalyst. After four cycles of photocatalytic CO₂ reduction reaction experiments, it still gives constant CO evolution rate and the catalyst is stable. Furthermore, the thermal behavior research indicates Ga-PKU-1:xFe³⁺ could maintain structural stability at 400 °C.

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