In situ preparation of Z-scheme MoO 3 /g-C 3 N 4 composite with high performance in photocatalytic CO 2 reduction and Rh
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Ying Wu Institute of Physical Chemistry, Zhejiang Normal University, Jinhua 321004, China
Yiming Hea) Department of Materials Science and Engineering, Zhejiang Normal University, Jinhua 321004, China (Received 13 May 2017; accepted 22 June 2017)
This research was designed for the first time to investigate the photocatalytic activities of MoO3/g-C3N4 composite in converting CO2 to fuels under simulated sunlight irradiation. The composite was synthesized using a simple impregnation-heating method and MoO3 nanoparticles was in situ decorated on the g-C3N4 sheet. Characterization results indicated that the introduction of MoO3 nanoparticles into g-C3N4 fabricated a direct Z-scheme heterojunction structure. The effective interfacial charge-transfer across the heterojunction significantly promoted the separation efficiency of charge carriers. The optimal CO2 conversion rate of the composite reached 25.6 lmol/(h gcat), which was 2.7 times higher than that of g-C3N4. Additionally, the synthesized MoO3/g-C3N4 also presented excellent photoactivity in RhB degradation under visible-light irradiation.
I. INTRODUCTION
To solve future energy limitations in nonrenewable fuels, it is needed to take the burden off the dependency on fossil fuels. The photocatalytic conversion of CO2 into useful fuels (such as CO, CH4, or CH3OH) is considered one of the most promising strategies to address this crisis.1–5 Since Inoue et al. first reported the photocatalytic reduction of CO2 to hydrocarbon fuels,1 many research groups had devoted their efforts in developing an efficient photocatalyst. The polymer semiconductor of g-C3N4 has inspired a great deal of interests due to the merits of high stability, moderate band gap, and low cost. Meanwhile, various semiconductors are coupled with g-C3N4 to fabricate heterostructured composite to improve the photocatalytic efficiency.6–10 For example, Ohno et al. reported that the doping of WO3 on g-C3N4 could increase the CH3OH yield by a factor of 2.4.11 He et al. used Ag3PO4 to modify g-C3N4, yielding an increased CO2 conversion of 57.5 lmol/(h gcat) which was 6-fold higher than that of naked C3N4.12 Zou et al. synthesized g-C3N4/N–TiO2 composite which was proved to be an effective photocatalyst for selective reduction of CO2 to CO.13 The similar examples are NaNbO3/g-C3N4,14 ZnO/g-C3N4,15 and P/g-C3N4.16 Among them, Z-scheme-type composite photocatalysts attract much attention due to the special charge-transfer mechanism.17,18 Take Ag3PO4/g-C3N4 as Contributing Editor: Xiaobo Chen a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2017.271
an example,12 the photogenerated electrons in the conduction band (CB) of the Ag3PO4 would annihilate the holes in the valence band (VB) of g-C3N4 via Z-scheme model, leading to the electron in the CB of g-C3N4 and holes in Ag3PO4. On the contrary, if the Ag3PO4/g-C3N4 sample follows type-II mechanism,14 the photogenerated electron and holes would be enriched on the CB of Ag3PO4 and the VB of g-C3N4, respectively. Given the stronger re
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