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Chemical Engineering Journal
journal homepage: www.elsevier.com/locate/cej
Synergistic effects of 2D/2D ZnV
2
O
6
/RGO nanosheets heterojunction for
stable and high performance photo-induced CO
2
reduction to solar fuels
Abdullah Bafaqeer, Muhammad Tahir
⁎
, Nor Aishah Saidina Amin
Chemical Reaction Engineering Group (GREG), Faculty of Chemical and Energy Engineering, Universiti Teknologi Malaysia, 81310, UTM, Johor Bahru, Johor, Malaysia
GRAPHICAL ABSTRACT
ARTICLE INFO
Keywords:
Novel ZnV
2
O
6
nanosheets
2D/2D structure
RGO
CO
2
reduction
CH
3
OH production
Visible light
ABSTRACT
Highly photo-stable and efficient 2D/2D zinc vanadium oxide-reduced graphene oxide (ZnV
2
O
6
/RGO) na-
nosheets heterojunction was fabricated by the one-pot solvothermal method. The structures and properties of the
catalysts were analyzed by XRD, FE-SEM, EDX, TEM, BET, UV–vis, Raman and PL spectroscopy. The 2D/2D
ZnV
2
O
6
/RGO catalyst shows excellent performance towards CO
2
photo-reduction with H
2
O to CH
3
OH,
CH
3
COOH and HCOOH under visible light. The yield of the main product CH
3
OH of 5154 μmol g-cat
-1
, obtained
over ZnV
2
O
6
/4%RGO, was 1.6 times the amount of CH
3
OH produced over the pure ZnV
2
O
6
(3254 μmol g-cat
-1
)
and a 5.5-fold higher than that of the ZnO/V
2
O
5
composite (945 μmol g-cat
-1
). In addition, CH
3
OH selectivity of
39.96% achieved over the ZnO/V
2
O
5
composite increased to 68.89% in ZnV
2
O
6
/4%RGO. The continuous and
selective production of CH
3
OH was detected over the entire irradiation time in ZnV
2
O
6
and ZnV
2
O
6
/4%RGO
samples, whereas the yield of products gradually decreased in ZnO/V
2
O
5
. The significant improvement in photo-
activity over 2D ZnV
2
O
6
structure was due to the hierarchical structure with enhanced charges separation. A
combined 2D/2D ZnV
2
O
6
/RGO nanosheets prevailed as a promising strategy to ameliorate the photocatalytic
performance of ZnV
2
O
6
nanosheets due to efficient trapping and transport of electrons by RGO. The synergistic
effects in ZnV
2
O
6
/RGO 2D/2D nanosheets exhibited excellent photocatalytic stability, which prevailed even
after 32 h of operation time for selective and continuous CH
3
OH production. A proposed photo-induced reaction
mechanism, corroborated with the experimental data, was also deliberated.
1. Introduction
Due to global warming caused by a remarkable increase of carbon
dioxide (CO
2
) emission into the atmosphere, it is currently a great
challenge to convert CO
2
into valuable fuels [1,2]. Artificial
photosynthesis process to convert CO
2
into useful carbon sources such
as CO, HCOOH, HCHO, CH
3
OH, and CH
4
is an attractive alternatives
because of the demand for methods to recycle CO
2
as a natural resource
[3–8]. The solar photocatalytic conversion of CO
2
into industrially
beneficial compounds offers one prospective path [9,10]. Sunlight is
https://doi.org/10.1016/j.cej.2017.11.111
Received 22 June 2017; Received in revised form 25 October 2017; Accepted 21 November 2017
⁎
Corresponding author.
E-mail address: mtahir@cheme.utm.my (M. Tahir).
Chemical Engineering Journal 334 (2018) 2142–2153
Available online 22 November 2017
1385-8947/ © 2017 Elsevier B.V. All rights reserved.
T