Tailoring the composition of a non-noble, Cubic Shaped MnSn(OH)6 Bi-functional electrocatalysts for methanol and urea oxidation reactions in alkaline solutions

Abstract

A systematic study of the effect of Sn-precursor concentration on the composition of (MnSn(OH)6) is carried out, and the samples' structural, morphological, and electrochemical variations are investigated. Four different SnCl2·5H2O precursor concentrations (5, 10, 20, and 40 mM) are varied to synthesize MnSn(OH)6 electrocatalysts, denoted as MS-1, MS-2, MS-3, and MS-4, respectively, using a hydrothermal method. All four samples' crystal structure and chemical states are identified using X-ray diffraction analysis and X-ray photoelectron microscopy. Morphological studies are carried out using scanning electron and transmission electron microscopy studies. The electrocatalytic performance and the stability of the synthesized samples are evaluated using cyclic voltammetry and chronoamperometry. Among the samples, MS-3, which has an optimized ratio of Mn/Sn, displayed the highest current density values of 80.3 mA g−1 and 84.7 mA g−1 at a higher potential of 0.7 V for the urea oxidation reaction in the presence of 0.33 M urea + 1.0 M KOH and for the methanol oxidation reaction in the presence of 0.5 M methanol + 1.0 M KOH, respectively. This intrinsic activity of MS-3 samples is due to its more significant electrochemically active surface area value of 208 mF cm−2, primarily because of the dominance of Mn3+ on the surface. Furthermore, MS-3 displayed reduced overpotential, as evidenced by the onset potential of 1.45 (V vs RHE) @ 10 mA cm−2, indicating enhanced electrocatalytic performance. These findings highlight the importance of tuning the Mn/Sn metal ratio to design and develop cost-effective non-precious electrocatalysts for urea and methanol oxidation reactions.