Synthesis of highly dispersed CeO2 nanoparticles on N-doped reduced oxide graphene and their electrocatalytic activity toward H2O2

Accepted Manuscript Synthesis of highly dispersed CeO2 nanoparticles on N-doped reduced oxide graphene and their electrocatalytic activity toward H2O2 Suling Yang, Gang Li, Guifang Wang, Lixin Liu, Dan Wang, Lingbo Qu PII:

S0925-8388(16)32146-6

DOI:

10.1016/j.jallcom.2016.07.113

Reference:

JALCOM 38281

To appear in:

Journal of Alloys and Compounds

Received Date: 25 January 2016 Revised Date:

17 June 2016

Accepted Date: 12 July 2016

Please cite this article as: S. Yang, G. Li, G. Wang, L. Liu, D. Wang, L. Qu, Synthesis of highly dispersed CeO2 nanoparticles on N-doped reduced oxide graphene and their electrocatalytic activity toward H2O2, Journal of Alloys and Compounds (2016), doi: 10.1016/j.jallcom.2016.07.113. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT Graphical abstract CeO2 nanoparticles (CeO2NP) supported on nitrogen-doped reduced graphene oxide (N-rGO) was synthesized. Based on this material, an electrochemical sensor for H2O2 was fabricated. The sensor

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exhibited superior electrocatalytic activity toward H2O2.

ACCEPTED MANUSCRIPT Synthesis of highly dispersed CeO2 nanoparticles on N-doped reduced oxide graphene and their electrocatalytic activity toward H2O2 Suling Yanga, b*, Gang Lia, b, Guifang Wanga, b, Lixin Liua, b, Dan Wanga, b, Lingbo Qua, b, c∗ a

College of Chemistry and Chemical Engineering, Anyang Normal University，Anyang 455002, PR

b

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China

Henan province key laboratory of new optoelectronic functional materials, Anyang Normal University，Anyang 455002, PR China

Luoyang Inst Sci & Technol, Dept Environm Engn & Chem, Luoyang 471023, PR China

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c

Abstract

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N-doped reduced oxide graphene (N-rGO) was successfully attached with CeO2 nanoparticles (CeO2NP) through a simple design rout by using ethylenediamine as N source and reduce agent. CeO2 with particle size distribution of 1–5 nm was highly coated on N-rGO. Scanning electron microscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, X-ray diffraction and

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electrochemistry were used to investigate the nanocomposite. In order to characterize the electro-catalysis of the as-prepared nanocomposite, CeO2NP/N-rGO-modified electrode toward the

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electrochemical response of H2O2 was recorded. The experimental results displayed that the as-prepared nanocomposite exhibited a better electrocatalytic property for H2O2. The possible synthesis

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mechanism and electro-catalytic mechanism of the as-prepared nanocomposite were proposed. Keywords: CeO2 nanoparticles; N-doped reduced oxide graphene; H2O2; electrocatalysis 1. Introduction

H2O2 participates in many important enzyme reactions, and plays a vital role in numerous fields, for example, food, pharmaceuticals as well as industrial and environmental analysis. Thus, it is

∗

Corresponding author. Tel.: +86 03722900040; Fax: +86 3722900040

E-mail address: [email protected] (S. Yang)

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ACCEPTED MANUSCRIPT necessary to establish a reliable, sensitive, rapid and reagentless method for the detection of H2O2. To date, many analytical techniques have been employed for the analysis of H2O2, including fluorescence [1], colorimetric method [2], high-performance liquid chromatography [3] and electrochemical analysis

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[4]. Among the mentioned methods, electrochemical methods are characterized to be a cheap and effective strategy with many advantages, such as cheap apparatus, small device size, excellent sensitivity, simple operation and real-time monitoring. Usually, modified electrodes with the

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intervention of enzyme will accelerate the electron transfer between electrode and H2O2 [5, 6].

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Nevertheless, there are some problems in the enzyme-based sensors, such as expensive materials, poor stability, harsh operating environment, complex fixed program as well as easy denaturation. Currently, a number of designations have been employed to improve nonenzymatic sensors with good sensitivity, lower detecting limit and wider respond range. For example, many types of nonenzymatic sensors

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based on different materials have been realized for the detection of H2O2, such as, MnO2 nanowires–graphene nanohybrid paper electrode [7], CoHCFNPs/GR modified electrode [8], Ce-doped SrFeO3 modified electrode [9], and silver nanowire modified electrode [10].

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In recent decades，graphene has attracted great attention of scientists due to its unique surface area,

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thermal stability and fast electron transport [11]. While, N-doped graphene prepared from graphene has obtained considerable attention due to the outstanding properties, for instance, much more chemically active site, the abundantly usable N sources, high electrical conductivity and biological compatibility of C–N micro-environment [12]. In addition, recent studies have shown that the introduction of N atom in graphene not only enhances the interaction between graphene and nano-materials, but also increases the active site for the adsorption of metal nanomaterial to graphene and strengthens their catalytic activity [13].

According to Zhao’s report [14], MoS2/N-doped graphene displayed remarkable

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ACCEPTED MANUSCRIPT enhancing catalytic activity for the electrochemical reduction of oxygen compared to MoS2. Meng et al. [12] fabricated Pt nanoparticles/N-doped graphene modified electrode for electrochemical detection of H2O2, and showed that the as-prepared sensor provided better electro-catalytic activities than Pt

as a kind of enhanced materials for constructing electrochemical sensors.

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nanoparticles/graphene. These reported literatures revealed that N-doped graphene has huge potential

Transition metal oxides (TMO) are viewed as the most suitable alternative materials for

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electrochemical capacitors. Some advantages, for instance, large specific capacitance added with low

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resistance leading to a specific power which ameliorates them suitable for commercial use. However, the low electron conductivity and large volume change during repeated lithium insertion/extraction are the main problem when TMO are used as anode materials. Currently, an effective strategy to improve the electrochemical performance of TMO is to incorporate TMO with carbon material. Carbon material

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can be used as a uniform matrix and buffer to accommodate the volume change in TMO electrode whilst maintain the electron transport active [15]. For the preparation of TMO-carbon-based material, interest in TMO such as MnO2, Fe2O3, NiO has been largely stimulated [16–18]. Because of the direct

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and rapid transformation of Ce(III) and Ce(IV), CeO2 nanoparticles may be good candidate for

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electrochemical applications [19–21]. Additionally, use of the CeO2-N-doped graphene nanocomposite as an electrode material for electroanalysis has not previously been reported. We thus report here the easy preparation of CeO2-N-doped reduced oxide graphene nanocomposite and its enhanced electrochemical performance as the electrode material in electrochemical determination of H2O2. 2. Experimental 2.1. Preparation of the nanocomposite Firstly, oxide graphene was produced from spectral graphite according to Hummers’ method [22].

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ACCEPTED MANUSCRIPT Secondly, on the basis of the reported technique [23] with an improvement, CeO2NP/N-rGO was synthesized in a typical preparation process. In simple terms, amount of Ce(NO3)3· 6H2O was poured into 5 mL 1 mg/mL GO solution, and sonicated intensively for 50 min. And then, 0.25 mL

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ethylenediamine (EDA) was titrated dropwise; subsequently, the resulting brown suspension was subjected to high temperature and high pressure reaction at 180 °C for 24 h. Finally, the as-obtained nanocomposite was collected by centrifugation. The purified precipitate for further characterization and

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preparation of sensor was dried at 60 °C.

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2.2. Fabrication of sensors

In a typical process, the above obtained nanocomposite was manually ground with 0.8 g spectral graphite and 0.2 g silicone oil in a mortar for about 1 h to get homogeneous paste. The well-proportioned carbon paste was filled compactly into a glassy tube (d = 3 mm), and then a copper

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wire was inserted through one end of the glassy tube to construct an electrical contact. Finally, CeO2NP/N-rGO modified carbon paste electrode (CPE) was obtained. The electrode surface was polished on a piece of weighing paper just before use. In order to facilitate comparison, a bare CPE,

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CeO2/CPE as well as N-rGO/CPE were prepared by the similar process.

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2.3. Characterization of sensor materials The morphologies of N-rGO anchored CeO2NP were examined by a JEM-2000 transmission

electron microscope (TEM) (JEOL Japan). Scanning electron microscope (SEM) was used on a Hitachi S-4800. X-ray photoelectron spectroscopy (XPS) was realized on a ThermoFisher-VG Scientific (ESCALAB 250Xi) photoelectron spectrometer. X-ray diffraction (XRD) was executed on a Siemens D500 diffractometer with a Cu Kα source (1.54056 Å). Electrochemical analysis was carried out on CHI 660E electrochemical system (Shanghai Chenhua Instrument Co., Ltd. Shanghai, China). A

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ACCEPTED MANUSCRIPT three-electrode system was recorded with a CeO2NP/N-rGO modified electrode as working electrode, an Ag/AgCl (3 M KCl) as reference electrode and a platinum wire electrode as auxiliary electrode, respectively.

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3. Results and discussion 3.1. Formation mechanism of the nanocomposite

The preparing process of the nanocomposite is displayed in Scheme 1. In the mixing process, Ce3+

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was uniformly anchored on GO surface, which benefited from the oxygen-containing groups. After the

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addition of EDA, Ce3+ was converted to Ce(OH)3. Under the conditions of 180 ℃ and high pressure, Ce(Ⅲ) was oxidized to Ce(Ⅳ) by GO and oxygen from the air [24]. Subsequently, the obtained solution was suffered from hydrothermal reduction to synthesize the CeO2NP/N-rGO. A deductive reaction mechanism for the formation of CeO2NP/N-rGO composite is shown below：

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Ce3+ + EDA + H2O →Ce(OH)3

(1)

Ce(Ⅲ) + GO →Ce(Ⅳ) Ce(Ⅲ) + O2→Ce(Ⅳ)

(2) (3)

GO + ne

(4)

－

→ N-rGO

(Please insert Scheme 1)

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Ce(OH)4 →CeO2 + H2O

3.2. Characterization of the nanocomposite The morphologies of the as prepared nanocomposite were characterized by SEM and TEM in

Fig.1. From Fig. 1A, CeO2NP exhibited milk-white particles due to the light scattering of the nanoparticles. It can be seen that CeO2 nanoparticles are uniformly distributed on the surface of N-rGO. TEM image (Fig. 1B) displays the transparent N-rGO and uniform distribution of CeO2NP on the N-rGO sheet’s surface. It is further indicating that the size of CeO2 nanoparticles is smaller than 5 nm.

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ACCEPTED MANUSCRIPT Fig. 2 is the XRD pattern of GO, N-rGO, free CeO2 and CeO2NP/N-rGO composite. For GO, the characteristic diffraction peak centered at 9.9° (0 0 2) is shown. However, after the chemical reduction of GO and introduction of N atom, the characteristic peak of GO disappears and the diffraction peak

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centers at～24° in consistent with the reported value [14], which is regarded as the hexagonal structure of N-rGO. For the XRD pattern of free CeO2 and CeO2NP/N-rGO hybrids, the peak of GO at 9.9° disappears, all the diffraction peaks can be indexed to cerianite structure CeO2 (JCPDS no.43-1002)

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N-rGO sheets are sufficiently separated by the loaded CeO2.

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for both CeO2NP/N-rGO and free CeO2. The diffraction peaks of N-rGO is dimly visible indicates that

In order to get the chemical state and the atomic surface composition of CeO2NP/N-rGO, XPS was carried out. The XPS spectra of C, O, N and Ce elements are shown in Fig. 3. The appearance of O and Ce elements confirms the successful preparation of CeO2 nanoparticles. At the same time, the

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presence of N element indicates the successful N doping by using the hydrothermal method with EDA. The high resolution XPS C1s spectrum (Fig. 3b) is deconvoluted into four subpeaks, suggesting the observation of four types of carbon. The peaks at 284.6, 286.4 and 290.0 eV are assigned to C＝C/C−C,

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C＝O, and O−C＝O [17]. It is worth noting that the existence of the peak at 285.3 eV corresponding to

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C−N makes sure the formation of the covalent bonds between nitrogen and graphene sheets [16]. In the high resolution XPS N1s spectrum (Fig. 3c), the peaks at 398.4, 399.5, 401.1 and 403.2 eV are assigned to pyridinic N, pyrrolic N, graphitic N, and oxidized N, respectively. The Ce 3d spectrum is presented in Fig. 3d. This spectrum combines the Ce 3d3/2 and Ce 3d5/2 spectra. The peak at 898.54 eV is assigned to Ce2+. The peak at 888.5 eV is assigned to Ce3+; and peaks at 882.60, 901.2, 907.60 and 916.94 eV are assigned to Ce4+ [25], which further indicates that the CeO2 nanoparticles have formed in CeO2NP/N-rGO composite.

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ACCEPTED MANUSCRIPT To characterize graphene-based materials, Raman scattering is an essential tool, especially for distinguishing ordered and disordered crystal structure of carbon and carbon-heteroatom from carbon–carbon bonds. Raman spectra of the as-prepared CeO2NP/N-rGO, N-rGO and rGO are given in

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Fig. 4. For comparison, the spectrum of rGO obtained from thermal reduction of GO under the same conditions is displayed. It is obvious that Raman spectra of all the samples shows the characteristic D-band (～1345 cm–1) and G-band (～1577 cm–1), corresponding to the characteristic D and G bands

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of carbon materials, respectively. Generally speaking, in the Raman spectra of graphene, the D band

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represents the structural defects and disordered structures, while the G band is assigned to the E2g vibration mode of sp2 domain indicative of the degree of graphitization [26]. Commonly, the D/G intensity ratio (ID/IG) is often used to reflect the structural disorder. The as-prepared N-rGO is found to have the high ID/IG of 1.04, obviously larger than the ID/IG of 0.94 observed for rGO, which is attributed

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to the structural defects caused by heterogeneous nitrogen atoms insertion into the rGO layers [27]. After CeO2NP/N-rGO composite formation, the increase in intensity ratio for D/G (1.12) is observed. This confirms successful deposition of CeO2NP on N-rGO sheets [28].

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(Please insert Fig. 1, Fig. 2, Fig. 3 and Fig. 4)

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3.3. Electrochemical characteristics of the modified electrode

As shown in the Fig. 5, the electrochemical impedance spectroscopy (EIS) of different electrodes

was recorded, which can exhibit the impedance change of the electrode interface. The interface can be simulated by an equivalent circuit (seen in the inset of Fig. 5). This equivalent circuit comprises the ohmic resistance of the electrolyte (Rs), the electron transfer resistance (Ret), the double layer capacitance (Cdl), and Warburg impedance (Zw). The Ret value was obtained as 78 Ω on the bare CPE. While on the CeO2/CPE, the Ret value was decreased to 348 Ω due to the introduce of semiconducting 7

ACCEPTED MANUSCRIPT CeO2, which decreased the electron transfer rate of Fe(CN)63−/4−. For N-rGO/CPE, the Ret value was decreased to 13 Ω, which may be due to the good electrical conductivity of graphene sheets, and improve the electron transfer of Fe(CN)63−/4−. However, the CeO2NP/N-rGO hybrid/CPE showed a

(Please insert Fig. 5)

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3.4. Electrochemical response of the modified electrode to H2O2

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very low Ret of 26 Ω. The results confirmed that CeO2NP have anchored on the surface of graphene.

In order to evaluate the catalytic properties of the modified electrode to the oxidation of H2O2,

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cyclic voltammograms (CVs) were recorded. Fig. 6A shows the CVs of CeO2NP/N-rGO/CPE (a), CPE (b), CeO2/CPE (c), and N-rGO/CPE (d) in the presence of 5 mM H2O2 and CeO2NP/N-rGO/CPE (e) without H2O2 in 0.1 M phosphate buffer (pH 7.0), respectively. Redox peaks were not observed on the

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above electrodes. When 5.0 mM H2O2 was added into the electrolyte, the oxidation current on the CeO2NP/N-rGO/CPE intensively increased. These experimental results revealed that CeO2NP/N-rGO displayed great electro-catalytic activity toward H2O2. The increasing electro-catalytic feature may be

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due to the synergistic effect of N-rGO and CeO2NP. The uniformly dispersed and high-loading amount

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of CeO2NP can offer high catalytic active site for the H2O2 oxidation. The efficient electrical network through CeO2NP directly firming on the surface of N-rGO can provide fast electron transfer channel. The huge surface area and excellent conductivity of N-rGO causes the electron transfer in CeO2NP/N-rGO/CPE intensively higher than that of CeO2/CPE, leading to fast electro-oxidation of H2O2 correspondingly. Based on the experimental results and the direct and rapid transform of Ce(III) and Ce(IV), it is logical to believe that CeO2 nanoparticles may act as the catalytic active sites, and the CeO2NP-Ce(III)/Ce(IV) redox couple possibly play roles in the oxidation of H2O2. According to the

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ACCEPTED MANUSCRIPT Ref. [19–21, 29], the possible electrocatalytic mechanism may undergo the following steps. Firstly, H2O2 was adsorbed on the surface of CeO2NP/N-rGO/CPE; secondly, CeO2NP-Ce(IV) is reduced to lower states by the absorbed H2O2; thirdly, lower states of CeO2NP-Ce(III) are electro-oxidized back to

CeO2NP-Ce(IV) + H2O2 → CeO2NP-Ce(III) + O2 + H2O

(1)

CeO2NP-Ce(III) → CeO2NP-Ce(IV) + e–

(2)

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CeO2NP-Ce(IV) on the electrode surface.

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To further verify the electro-catalytic effect of CeO2NP/N-rGO, amperometric curve was

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investigated. As can be seen from Fig. 6B, compared to CPE (b), CeO2NP/CPE (c), and N-rGO/CPE (d), the highest current response of CeO2NP/N-rGO/CPE (a) was displayed, and it was almost 5 times larger than that got on the bare CPE, which well revealed the considerable electro-catalytic activity of nanocomposite toward the oxidation of H2O2.

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(Please insert Fig. 6)

3.5. Effect of applied potential

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The applied potential for the amperometric sensing of H2O2 was optimized in the potential range of 0.50 to 0.70 V. Fig. 7 shows the amperometric response curves of CeO2NP/N-rGO/CPE at different

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applied potentials in 80 µM H2O2 solutions. Obviously, the amperometric currents increase with positive shift of applied potential, and reach a maximum value at a potential of 0.70 V, but the amperometric response current is starting to lose rapidly at 0.70 V. Therefore, the applied potential for the amperometric H2O2 sensor was defined as 0.65 V to ensure enough sensitivity and stability.

3.6. Effect of buffer pH

The buffer pH could influence the amperometric response of H2O2. The pH of the supporting

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ACCEPTED MANUSCRIPT electrolyte on the amperometric response of of 0.25 mM H2O2 on CeO2NP/N-rGO/CPE was investigated in the range from 4.0 to 9.0. As can be seen from Fig. 8, with the increase of pH in the range of 4.0−7.0, the amperometric response currents increases firstly, and then decreases with the

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increase of pH in the range of 7.0−9.0. When pH is more than 7.0, the amperometric response current is unstable. Therefore, considering the maximum amperometric current and stability, pH 7.0 is selected as

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the supporting electrolyte for the detection of H2O2 in this study.

(Please insert Fig. 7 and Fig. 8)

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3.7. Amperometric sensing of H2O2 and interferences

Under the optimal experimental conditions, amperometric detection was used for the analysis of H2O2. Fig. 9 displays the amperometric response of the CeO2NP/N-rGO/CPE for the successive addition of amount of H2O2 in 0.1 M phosphate buffer (pH 7.0) at an applied potential of 0.65 V under

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stirring. A rapid response is realized with the addition of H2O2. As shown in Fig. 9 inset, the current response is linear with H2O2 concentration in the range of 1.8–920.8 µM. The detection limit was

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estimated to be 1.3 µM (S/N = 3), which was lower than the reported enzymatic biosensor [30] and MnO2-ERGO paper electrode [7]. Based on different modified materials, a comparison for H2O2

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detection is listed in Table 1. As can be seen from Table 1, the CeO2NP/N-rGO/CPE shows a broader detection range and a lower detection limit. The possible coexisting substances, such as some ions, organic compounds and electroactive

compound, were investigated with the response of H2O2. Under the optimal conditions, the interference study was recorded by comparing the response current of 0.01 mM H2O2 plus each interfering substance with that of 0.01 mM H2O2 alone. The results obtained are listed in Table 2. When the concentration of K+, Ca2+, Cl−, NO3−, SO42−, carbamide, glycin, glucose and acetate are 100 times more

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ACCEPTED MANUSCRIPT than that of 0.01 mM H2O2, ascorbic acid 1 time, as well as Zn2+, Al3+ 5 times, no observable interference are observed in the detection of H2O2 according to the relative error < ±10%. (Please insert Fig. 9, Table 1 and Table 2)

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3.8. Reproducibility and stability of the sensor Regeneration and reproducibility for the modified electrode were investigated. When the same modified CPE was used for six times successive measurements of 0.01 mM H2O2, the relative standard

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deviation (RSD) of the current response was 6.4%. The stability of the modified electrode was

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evaluated by studying the steady-state response current of H2O2 every day, the RSD of steady-state response current was 4.1%. When not in use, the modified electrode was stored at room temperature. The steady-state current response decreased by 8.7% after 7 days, indicating that the fabricated sensor was considerably stable.

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4. Conclusions

In summary, a novel CeO2NP/N-rGO nanocomposite was synthesized successfully via a simple hydrothermal reaction. CeO2 nanoparticles are smaller than 5 nm-diameter and uniformly distributes on

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the surface of N-rGO. Subsequently, a nonenzymatic sensor for H2O2 was successfully constructed by

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using the nanocomposite in CPE. The resultant sensor shows a high electro-catalytic activity for H2O2 due to its attractive characteristics, such as wider linear range, lower detection limit, as well as high sensitivity. The synergetic effect of the high catalytic nature of CeO2NP and the large surface area of N-rGO also makes it possible to be applied in other chemical or biological determinations. Acknowledgments The authors gratefully acknowledge the financial support from Nature Science Foundation of Anyang Normal University and National Natural Science Foundation of China (NSFC, No.21102005).

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[26] A.C. Ferrari, J.C. Meyer, V. Scardaci, C. Casiraghi, M. Lazzeri, F. Mauri, S. Piscanec, D. Jiang, K.

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Novoselov, S. Roth, Raman spectrum of graphene and graphene layers, Phys. Rev. Lett. 97 (2006)

[27] D. Jiang, Q. Liu, K. Wang, J. Qian, X. Dong, Z. Yang, X. Du, B. Qiu, Enhanced non-enzymatic glucose sensing based on copper nanoparticles decorated nitrogen-doped graphene, Biosens.

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Bioelectron. 54 (2014) 273–278.

[28] A.C. Joshi, G.B. Markad, S.K. Haram, Rudimentary simple method for the decoration of graphene oxide with silver nanoparticles: Their application for the amperometric detection of glucose in the

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human blood samples, Electrochim. Acta 161 (2015) 108–114.

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[29] D. Ye, H. Li, G. Liang, J. Luo, X. Zhang, S. Zhang, H. Chen, J. Kong, A three-dimensional hybrid of MnO2/graphene/carbon nanotubes based sensor for determination of hydrogen-peroxide in milk, Electrochim. Acta 109 (2013) 195–200.

[30] X. Yang, F.B. Xiao, H.W. Lin, F. Wu, D.Z. Chen, Z.Y. Wu, A novel H2O2 biosensor based on Fe3O4–Au magnetic nanoparticles coated horseradish peroxidase and graphene sheets–Nafion film modified screen-printed carbon electrode, Electrochim. Acta 109 (2013) 750–755. [31] Z.P. Wu, S.W. Yang, Z. Chen, T.T. Zhang, T.T. Guo, Z.F. Wang, F. Liao, Synthesis of Ag

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glass carbon electrode, Talanta 120 (2014) 484–490.

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based on Ni(OH)2/electroreduced graphene oxide multiwalled carbon nanotube film modified

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ACCEPTED MANUSCRIPT Figures and captions Fig. 1. SEM (A) and TEM (B) images of the CeO2NP/N-rGO composites. Fig. 2. XRD pattern of GO, N-rGO and CeO2NP/N-rGO composite.

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Fig. 3. XPS survey scan (a), C 1s spectrum (b), N 1s spectrum (c), and Ce 3d spectrum (d) of CeO2NP/N-rGO composite. Fig. 4. Raman spectra of CeO2NP/N-rGO, N-rGO and rGO.

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Fig. 5. The EIS of CeO2NP/N-rGO/CPE (a), CPE (b), CeO2/CPE (c), and N-rGO/CPE (d). EIS condition: frequency range: 105–0.1 Hz; potential: 0.250 V; perturbation amplitude: 5 mV;

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solution: 1.0 mM Fe(CN)6 3−/4− and 0.1 M KCl solution.

Fig. 6. CVs of CeO2NP/N-rGO/CPE (a), CPE (b), CeO2/CPE (c), and N-rGO/CPE (d) in the presence of 5.0 mM H2O2 and CeO2NP/N-rGO/CPE (e) without H2O2 in 0.1M phosphate buffer (pH 7.0);

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Scan rate: 20 mV/s. (B) i–t curves of CeO2NP/N-rGO/CPE (a), CPE (b), CeO2NP/CPE (c), and N-rGO/CPE (d) for two successive addition of 0.5 mM H2O2 at an applied potential of 0.65 V. Fig. 7. Amperometric response of the modified electrode upon the two successive additions of 80 µM

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H2O2 in 0.1 M phosphate buffer (pH 7.0) at different applied potentials.

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Fig. 8. Amperometric response of 0.25 mM H2O2 on CeO2NP/N-rGO/CPE in 0.1 M phosphate buffer at various pH values. Applied potential of 0.65 V.

Fig. 9. Amperometric response of the modified electrode (holding at 0.65 V) upon addition of H2O2 to increasing concentrations in 0.1 M phosphate buffer (pH 7.0); the inset is linear relationship between the current and concentration of H2O2. Scheme 1 Illustration of the synthesis of CeO2NP/N-rGO nanocomposite. Table 1 Comparison of electrodes based on different materials for H2O2 determination. Table 2 Results of interfering experiment. 17

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Fig. 1

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Fig. 2

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Fig. 5

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Fig. 7

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Fig. 8

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Fig. 9

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Scheme 1

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Table 1

Detection limit (µM)

References

MnO2–ERGO paper

100–45400

10

[7]

CoHCFNPs/GR/CCE

0.6–379.5

0.1

[8]

Ce-doped SrFeO3

0-500

10

[9]

AgNW

8 –30

46

[10]

20–2500

12

[30]

100–10000

0.88

[31]

Ni(OH)2/ERGO-MWNT

10–9050

4.0

[32]

CeO2NP/N-rGO

1.8−920.8

SPCE/GS–Nafion/Fe3O4-Au-HRP

1.3

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AgNP-PmPD

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Linear range (µM)

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Electrode material

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Table 2 Interferent

Concentration (mM)

Current ratioa

K+

1.0

0.910

2+

1.0

0.923

−

Cl

0.940

1.0

0.900

2−

1.0

0.986

carbamide

1.0

1.010

glycin

1.0

0.991

acetate

1.0

0.972

ascorbic acid

0.01

Zn2+

0.05

Al3+

0.05

NO3

a

1.098

1.051

1.076

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1.0 −

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Ca

Ratio of currents for mixtures of interferents and 0.01 mM H2O2 compared to that for 0.01 mM

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H2O2 alone. Applied potential: 0.65 V. Electrolyte: 0.1 M phosphate buffer (pH 7.0).

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ACCEPTED MANUSCRIPT Highlights

• Novel CeO2 nanoparticles/nitrogen-doped reduced graphene oxide is prepared by a simple method. • As a sensitive electrode material, it exhibited superior electrocatalytic activity toward H2O2.

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• The excellent electro-catalytic property resulted from the synergistic effect of N-rGO and CeO2NP.

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• The material synthesis mechanism and electrocatalytic mechanism were proposed firstly.