Citation: Silwana, B.; Matoetoe, M. Heterostructure of Metal Oxides Integrated on a GCE for Estimation of H 2 O 2 Capacity in Milk and Fruit Juice Samples. Electrochem 2023, 4, 56–67. https://doi.org/10.3390/ electrochem4010006 Academic Editor: Ítala Marx Received: 25 November 2022 Revised: 19 January 2023 Accepted: 1 February 2023 Published: 10 February 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). electrochem Article Heterostructure of Metal Oxides Integrated on a GCE for Estimation of H 2 O 2 Capacity in Milk and Fruit Juice Samples Bongiwe Silwana and Mangaka Matoetoe * Department of Chemistry, Cape Peninsula University of Technology, Tennant Street, Cape Town P.O. Box 652, South Africa * Correspondence: matoetoem@cput.ac.za Abstract: High levels of H 2 O 2 in food can lead to oxidative stress. Which has been linked to a number of neurological diseases. Hence, its detection in beverages is essential. However, a complicated structure of the reaction medium of H 2 O 2 makes the detection procedure very difficult. For this reason, sensitive strategic methods are required. In this study, quantification of H 2 O 2 in milk and apple juice has been obtained via the electrochemical sensing platform based on GCE/SiO-CeONPs. Scanning Electron Microscopy (SEM), Cyclic voltammetry(CV), and electron impedance spectroscopy(EIS) were employed to characterize the composite. The kinetics investigation of the sensor with H 2 O 2 revealed an a quasi-reversible one -electron adsorption process. Under optimized conditions, the Differential Pulse Voltammetry (DPV) in 0.1 M Phosphate buffer (PB) pH 5.5 of the H 2 O 2 displayed a peak at 0.13 V vs. Ag/AgCl with the detection limits of 0.0004 μM, linearity range of 0.01–0.08 μM. The observed LOD values of this method for real samples were calculated to be 0.006 μM and 0.007 μM with LOQ of 0.02 μM for milk and apple juice, respectively. The recovery of the analyte was from 92 to 99%. Furthermore, due to good selectivity and stability, the benefit of this sensor is its applicability in multiple fields. Keywords: H 2 O 2 ; SiO 2 ; CeO 2 ; beverage samples; DPV; GCE; sensor 1. Introduction The synthesis of novel functional nanomaterials with electro-catalytic properties for the development of sensors has resulted in an increase in these field of research. This is evident in the improvement of nanoscale materials in the food processing industry, medical, biological systems, paper bleaching process, textiles, disinfecting agents, and environmental protection [1–3]. Nowadays, semiconductors are of interest for commercial applications due to the high cost of coinage metals [4]. Metallic, polymeric materials and semiconductors have been reported to construct nonenzymatic hydrogen peroxide sensors. Mixed transition metal oxide nanoparticles results in good properties due to their different shapes, structures, and size [5]. Once the mixed oxide is formed, the acidic sites due to the excess negative or positive charge are displayed as a result of defects in the lattice [5,6]. The most important step in metal oxide synthesis is the metal–oxygen–metal bond creation. The working electrode surface can be modified with metal oxides and their mixtures using methods like physical adsorption, electro-polymerization, covalent bonding, and electrodeposition techniques. Metal oxide semiconductors have been widely reported as the ideal substrate for significant electrochemical study due to the high degree of ionic bonding and possess anti-fouling properties [7]. Thus, there are very interesting and useful for the detection of the analyte of interest in real samples. The non-toxicity of rare earth cerium oxide makes it a special oxide, placing it among metal oxide semiconductors, it is a size-dependent electrically conductive material and its chemically inert. Cerium Oxide is ambiguous, con- taining multiple valences of which the most used are Cerium (III) Oxide, Ce 2 O 3 otherwise Electrochem 2023, 4, 56–67. https://doi.org/10.3390/electrochem4010006 https://www.mdpi.com/journal/electrochem