Synthesis of Large Surface‐Area g‐C₃N₄ Comodified with MnO<i>_x</i> and Au‐TiO₂ as Efficient Visible‐Light Photocatalysts for Fuel Production

Abstract Herein, this study successfully fabricates porous g‐C 3 N 4 ‐based nanocomposites by decorating sheet‐like nanostructured MnO x and subsequently coupling Au‐modified nanocrystalline TiO 2 . It is clearly demonstrated that the as‐prepared amount‐optimized nanocomposite exhibits exceptional visible‐light photocatalytic activities for CO 2 conversion to CH 4 and for H 2 evolution, respectively by ≈28‐time (140 µmol g −1 h −1 ) and ≈31‐time (313 µmol g −1 h −1 ) enhancement compared to the widely accepted outstanding g‐C 3 N 4 prepared with urea as the raw material, along with the calculated quantum efficiencies of ≈4.92% and 2.78% at 420 nm wavelength. It is confirmed mainly based on the steady‐state surface photovoltage spectra, transient‐state surface photovoltage responses, fluorescence spectra related to the produced •OH amount, and electrochemical reduction curves that the exceptional photoactivities are comprehensively attributed to the large surface area (85.5 m 2 g −1 ) due to the porous structure, to the greatly enhanced charge separation and to the introduced catalytic functions to the carrier‐related redox reactions by decorating MnO x and coupling Au‐TiO 2 , respectively, to modulate holes and electrons. Moreover, it is suggested mainly based on the photocatalytic experiments of CO 2 reduction with isotope 13 CO 2 and D 2 O that the produced •CO 2 and •H as active radicals would be dominant to initiate the conversion of CO 2 to CH 4 .

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