Dual-centre Ag@SnO2/multiwalled carbon nanotubes electrocatalyst for hydrogen peroxide reduction

Background Efficient electrochemical reduction of hydrogen peroxide is important for catalytic, sensing, and energy-related electrochemical applications, while understanding the underlying electrode mechanism remains essential for the rational design of high-performance materials. Methods An Ag@SnO 2 /MWCNT hybrid nanocomposite was synthesized hydrothermally using SnCl 2 and silver acetate precursors, with citric acid as a complexing agent. Physico-chemical characterization confirmed the formation of SnO 2 nanostructures integrated with conductive multiwalled carbon nanotubes (MWCNTs), while Ag incorporation provided additional active sites and improved the electrode kinetics. The obtained composite was employed as a modified electrode for H 2 O 2 reduction in an alkaline medium. Significant findings Cyclic voltammograms recorded between 20 and 100 mV s −1 in the presence of 4 mM H 2 O 2 exhibited nearly invariant profiles with minimal current variation, indicating a complex electrocatalytic mechanism. The observed behaviour suggests surface-mediated disproportionation of H 2 O 2 on Ag sites, generating O 2 that is subsequently reduced electrochemically, thereby maintaining the interfacial H 2 O 2 concentration during catalysis. Additionally, cyclic voltammetry and square-wave voltammetry indicate an EC′-type mechanism at the Ag/SnO/SnO 2 heterojunction, where the SnO/SnO 2 redox couple acts as a mediator facilitating electron transfer. The developed electrode exhibited improved electrocatalytic performance toward H 2 O 2 reduction.