Oxygen-Evolution Activity of p-n Heterojunction NiO-SnO₂ Ceramic on Ti Substrate Fabricated Using a Simple...

To expand the application of p-n heterojunction NiO-SnO₂ ceramic materials from gas sensors and photoelectrocatalysts to oxygen-evolution reaction (OER) catalysts, we fabricated two NiO-SnO₂ ceramics on a Ti plate (NSCTs) using a simple layer-by-layer method. The prepared NSCTs (NSCT-480 and NSCT-600) were characterized and analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), diffuse reflectance ultraviolet-visible spectroscopy (DRUV-vis), and X-ray photoelectron spectroscopy (XPS). The OER activity and stability were measured by linear sweep voltammetry, cyclic voltammetry, chronoamperometry, amperometric i-t curve, and chronopotentiometry in a 1.0 mol/L NaOH solution at normal temperature and pressure. After 500 cycles, the lower overpotential (η = 194 mV at 1 mA/cm²) indicated that NSCT-600 offered adequate performance as an OER electrocatalyst. Moreover, the changes observed with cyclic voltammetry, SEM, XRD, and XPS during the OER test revealed that the redox cycle of Ni²⁺/Ni³⁺, morphology, and crystal faces of NiO and SnO₂ were three critical factors. The data proved that the NiO-SnO₂ ceramic is a stable OER electrocatalyst. The results of this study will provide a guide for the design and fabrication of p-n heterojunction metal-oxide ceramic electrocatalysts with a high OER performance.