Binder free Cobalt Phosphate electrocatalyst for alkaline water splitting at elevated electrolyte temperatures

Developing efficient, low-cost, and binder-free electrocatalysts for overall water splitting is essential for sustainable hydrogen production. In this work, cobalt–phosphorus-based catalyst coatings were directly grown on nickel foam using hydrothermal synthesis method. The binder-free configuration provides direct electrical contact, while the three-dimensional porous nickel foam framework supports electrolyte penetration, charge transport, and gas-bubble release during water-splitting reactions. The synthesis was conducted at a fixed hydrothermal temperature of 160 °C, while the reaction time was varied to control coating growth, morphology, and electrochemical performance. Among the studied reaction durations, the 10 h coated sample exhibited improved activity toward the oxygen evolution reaction in 1 M alkaline electrolyte. In addition to synthesis optimization, the effect of electrolyte temperature on water-splitting performance was investigated from 23°C(room tempearture ) to 80°C. An OER potential drop by 130 mV from 23°C to 80°C was observed with a lower tafel slope of 56mV/dec. The enhanced performance can be related to the optimized nanorod-like coating morphology, which promotes electrolyte accessibility, active-site exposure, and charge transfer during electrocatalytic reactions. Chronoamperometric stability testing was performed over 20 h at a fixed potential corresponding to 10 mA/cm², and an increasing current density was observed at 23–60°C, whereas performance declined at 80°C due to slight degradation. This study is important because practical alkaline water electrolyzers operate at elevated temperatures, where electrolyte conductivity, reaction kinetics, charge-transfer resistance, and bubble release behavior can significantly influence catalytic activity. Evaluating the catalyst under different electrolyte temperatures provides a more practical understanding of its performance under operating conditions.