Electronic Supplementary Material
Non-enzymatic photoelectrochemical sensing of hydrogen peroxide using hierarchically
structured zinc oxide hybridized with graphite-like carbon nitride
Xinguo Xi b, Jing Li a, Hongmei Wang a, Qi Zhao a, Hongbo Li a *
a School of Chemical and Biological Engineering, Yancheng Institute of Technology,
Yancheng 224051, P.R. China
b School of Materials Engineering, Yancheng Institute of Technology, Yancheng 224051, P.R.
China
*Corresponding Author, Phone & Fax: +86-515-88298735, E-mail: hbli@ycit.edu.cn
Condition optimization
The ZnO/g-C3N4 composites with different mass ratios (0 %, 1 %, 3 %, 5 %, 7 % and 9 %)
of g-C3N4 were investigated for their photocurrent responses. As shown in Figure S1A, the
photocurrent increased until 5 % composition and then decreased at the bias potential of 0.2 V
with simulated sunlight irradiation. It can be explained that the construction of ZnO/g-C3N4 is
favorable to the separation of the increased photo-generated carriers [1]. However, a larger
quantity proportion of g-C3N4 may prevent the electron transporting from the CB of g-C3N4 to
that of ZnO HSs and further decrease the photocurrent responses. Therefore, the optimum of
5 % composition is favorable for the further study. In addition, based on the same quantity in
the optimized ratio, the photocurrent response of single g-C3N4 has also been investigated (see
Figure S1B). Obviously, the photocurrent response of the optimized ZnO/g-C3N4 composite is
about 5-fold larger than that of single ZnO and 77-fold larger than that of single g-C3N4.
Figure S1. Effects of the mass ratio (A) of g-C3N4 to ZnO HSs on the photocurrent response
and the photocurrent response of single g-C3N4 (B) in 0.1 M PBS (pH 7.0) at a bias voltage of
0.2 V upon a 250 W tungsten halogen light excitation.
XPS Characterization of ZnO and C3N4
The composition and chemical status of the sample were also confirmed by XPS technique.
Figure S2 displays the X-Ray photoelectron survey spectrum (A), high-magnification of
g-C3N4 (B) and the corresponding high-resolution spectra of Zn 2p (C), O 1s (D), N 1s (E), C
1s (F) from the ZnO/g-C3N4. As can be seen in Figure 3(C), the two peaks at binding energies
of 1021 eV and 1044 eV correspond to the photo-splitting electrons, Zn2+ 2p3/2 and Zn2+ 2p1/2,
respectively. This indicates that Zn in the sample is in the form of Zn2+ [2]. Figure 3(D) shows
the O 1s binding energy of ZnO HSs at 529.5 eV and 531.3 eV, respectively, which can be
assigned to the metallic oxide (O2-) in the ZnO lattice [3]. The N 1s peak XPS spectrum is
deconvoluted into three Gaussian−Lorenzian peaks centered at 398.5, 400.2, and 403.5 eV
(Figure 3E), which can be attributed to the pyridinic-like nitrogen (N−sp2C), graphitic
nitrogen (N−(C)3), as well as the charging effects, respectively, in accordance with the
reported results [4]. As indicated in Figure 3F, the peak centered at 284.7 eV can be ascribed
to the C−C coordination of the surface adventitious carbon, whereas the peaks at 286.8 eV
and 289.4 eV correspond to C-N-C bonds and sp3-bonded C in C−N of g-C3N4, respectively
[5]. The above investigations strongly confirm that the composite of hierarchical structured
ZnO hybridized with g-C3N4.
Figure S2. X-Ray photoelectron survey spectrum (A), high-magnification of g-C3N4 (B) and
the corresponding high-resolution spectra of Zn 2p (C), O 1s (D), N 1s (E), C 1s (F) that are
obtained from the ZnO HSs/g-C3N4 (g-C3N4 contents: 5 wt %).
References
[1] Tang Y B, Chen Z H, Song H S, Lee C S, Cong H T, Cheng H M, Zhang W J, Bello I, Lee
S T (2008) Vertically aligned p-type single-crystalline GaN nanorod arrays on n-type Si for
heterojunction photovoltaic cells. Nano Lett 8: 4191
[2] Sun J X, Yuan Y P, Qiu L G, Jiang X, Xie A J, Shen Y H, Zhu J F (2012) Fabrication of
composite photocatalyst g-C3N4–ZnO and enhancement of photocatalytic activity under
visible light. Dalton Trans 41: 6756
[3] Lee J C, Lee J E, Lee J W, Lee J C, Subramaniam N G, Kang T W, Ahuja R (2014) Se
concentration dependent band gap engineering in ZnO1-xSex thin film for optoelectronic
applications. J Alloys Compd 585: 94
[4] Xu M, Han L, Dong S J (2013) Facile fabrication of highly efficient g-C3N4/Ag2O
heterostructured photocatalysts with enhanced visible-light photocatalytic activity. ACS Appl
Mater Interfaces 5: 12533
[5] Dai K, Lu L H, Liu Q, Zhu G P, Wei X Q, Bai J, Xuan L L, Wang H (2014) Sonication
assisted preparation of graphene oxide/graphitic-C3N4 nanosheet hybrid with reinforced
photocurrent for photocatalyst applications. Dalton Trans 43: 6295