High-efficiency conversion of CO2 to fuel over ZnO/g-C3N4 photocatalystApplied Catalysis B: Environmental


Yiming He, Yan Wang, Lihong Zhang, Botao Teng, Maohong Fan
Process Chemistry and Technology / Environmental Science (all) / Catalysis


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Applied Catalysis B: Environmental 168 (2015) 1–8

Contents lists available at ScienceDirect

Applied Catalysis B: Environmental j ourna l h om epage: www.elsev ier .com/ locate /apcatb

High-efficiency conversion of CO2 to fuel over Zn photoc

Yiming H aoh a School of Ener b Department o c College of Che d School of Civi SA a r t i c l

Article history:

Received 3 Jul

Received in re

Accepted 12 D

Available onlin





Fuel repa hotoc regn etho ron m

X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS), and photoluminescence spectroscopy (PL). The characterizations indicate that ZnO and g-C3N4 were uniformly combined. The deposition of ZnO on g-C3N4 showed nearly no effect on its light-absorption performance.

However, the interactions between the two components promoted the formation of a hetero-junction structure in the composite, inhibited the recombination of electron–hole pairs and, finally, enhanced the photocatalytic performance of ZnO/g-C N . The optimal ZnO/g-C N photocatalyst showed a CO con1. Introdu

Two urg is to seek a to the decre increase in C warming. Se challenges. solar-photo ation from from photo useful chem highly prom challenges. tocatalytic r made vario ∗ Correspon

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E-mail add http://dx.doi.o 0926-3373/© 3 4 3 4 2 version rate of 45.6 mol h−1 gcat−1, which was 4.9 and 6.4 times higher than those of g-C3N4 and P25, respectively. This work represents an important step toward artificial photocatalytic CO2 conversion to fuel using cost-efficient materials. © 2014 Elsevier B.V. All rights reserved. ction ent challenges currently confront humanity. The first clean and sustainable alternative energy source, due asing availability of fossil fuels; the other is the rapid

O2 emissions believed to be the primary cause of global veral approaches have been suggested to address these

Among these are CO2 capture and storage, as well as voltaic cells and solar fuels, including hydrogen generphotocatalytic water splitting and carbon-based fuels catalytic CO2 reduction. Of these, converting CO2 into icals and clean fuels (e.g., CO, CH4 or CH3OH) is a ising approach that might simultaneously address both

Since Halmann and Inoue et al. first reported the phoeduction of CO2 in the late 1970s [1,2], scientists have us attempts in the photocatalytic conversion of CO2 ding author at: School of Energy Resources, University of Wyoming, 2071, USA. Tel.: +1 307 766 5633; fax: +1 307 766 6667. ress: mfan@uwyo.edu (M. Fan). [3–9]. Although TiO2 is the most popular photocatalyst due to its robust reactivity, commercial availability and chemical stability, it can absorb only ultraviolet (UV) light, which occupies no more than 4% of the solar spectrum, thus significantly limiting its application.

Therefore, the development of an efficient photocatalyst with high activity under sunlight is needed.

Due to its moderate band gap (Eg = 2.7 eV) and high stability, graphitic carbon nitride (g-C3N4) has recently attracted significant attention as a novel, metal-free semiconductor. Wang et al. [10] first reported that g-C3N4 has high photocatalytic performance for hydrogen or oxygen production from water splitting under visiblelight irradiation. The application of g-C3N4 in water purification and

CO2 photoreduction has also been reported [11,12]. And since it can be easily prepared via heating melamine or urea, g-C3N4 is cheaper than TiO2. In addition, g-C3N4 has a much more negative conduction band (Ecb = −1.20 V) [10] than TiO2 (Ecb = −0.29 V) [13], which means that its photogenerated electrons have stronger reducibility, allowing it to reduce CO2 to CH3OH ECO2 /CH3OH = −0.32V or other hydrocarbon fuels [6] that cannot be generated over a TiO2 photocatalyst. However, despite its potential for CO2 photoreduction, the photocatalytic activity of g-C3N4 in CO2 reduction is still rg/10.1016/j.apcatb.2014.12.017 2014 Elsevier B.V. All rights reserved.atalyst ea,b, Yan Wanga, Lihong Zhangb, Botao Tenga,c, M gy Resources, University of Wyoming, Laramie, WY 82071, USA f Materials Physics, Zhejiang Normal University, Jinhua 321004, China mistry and Life Sciences, Zhejiang Normal University, Jinhua 321004, China l and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332, U e i n f o y 2014 vised form 3 November 2014 ecember 2014 e 17 December 2014 a b s t r a c t

The objective of this research was to p to fuel on a ZnO/g-C3N4 composite p lyst was synthesized by a simple imp including Brunauer–Emmett–Teller m spectroscopy (FT-IR), scanning electO/g-C3N4 ong Fana,d,∗ re, characterize and evaluate the conversion efficiency of CO2 atalyst under simulated sunlight irradiation. The photocataation method and was characterized by various techniques, d (BET), X-ray diffraction (XRD), Fourier transform infrared icroscopy (SEM), transmission electron microscopy (TEM), 2 Y. He et al. / Applied Catalysis B: Environmental 168 (2015) 1–8 low, necessitating the modification of g-C3N4 to improve its photocatalytic efficiency. The approach of coupling g-C3N4 with another semiconductor to construct a hetero-junction composite has been proven effective [14–17]. For example, Cao et al. reported that the doping of I of three [16 yielding tw three times


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