Potassium nitrate (KNO3) is widely utilized in concentrated solar power tower (CSPT) fuels and as an additive to address the issue of lithium dendrite formation in lithium-ion batteries and CSPT systems. This study investigates the influence of boron-doped diamond (BDD) films and their interaction with KNO3-saturated solutions to enhance these devices’ efficiency and energy capacity. One critical factor in achieving higher energy devices is the electrochemical stability window (ESW). Consequently, this research examines various properties of BDD, including grain size, doping level, conductivity, carbon-sp3/sp2 ratio, and electrolyte characteristics such as conductivity and pH. The results demonstrate that a BDD film grown at a B/C ratio of 2000 ppm, a grain size of 1.75 μm and a carbon-sp3/sp2 ratio value of 0.31 achieved the broadest ESW of 3.5 V. Advantageously, the properties of the KNO3 electrolyte, specifically concentration and pH, had minimal impact on the ESW. Controversially, the ionic conductivity of the electrolyte increased with concentration, with a peak value of 204 mS cm–1 observed in the supersaturated solution (3.78 mol kg–1).
