Undoped SnO₂ as a Support for Ni Species to Boost Oxygen Generation through Alkaline Water Electrolysis

In this study, the synergistic behavior of Ni species and bimodal mesoporous undoped SnO₂ is investigated in oxygen evolution reactions (OERs) under alkaline conditions without any other modification of the compositional phases or using noble metals. An efficient and environmentally friendly hydrothermal method to prepare bimodal mesoporous undoped SnO₂ with a very high surface area (>130 m² g^-1) and a general deposition-precipitation method for the synthesis of well-dispersed Ni species on undoped SnO₂ are reported. The powders were characterized by adsorption-desorption isotherms, TG-DTA, XRD, SEM, TEM, Raman, TPR-H₂, and XPS. The best NiSn composite generates, under certain experimental conditions, a very high TOF value of 1.14 s^-1 and a mass activity higher than 370 A g^-1, which are remarkable results considering the low amount of Ni deposited on the electrode (3.78 ng). Moreover, in 1 M NaOH electrolyte, this material produces more than 24 mA cm^-2 at an overpotential value of approximately +0.33 V, with only 5 wt % Ni species. This performance stems from the dual role of undoped SnO₂, on the one hand, as a support for active and well-dispersed Ni species and on the other hand as an active player through the oxygen vacancies generated upon Ni deposition.