Realistic electrolyzer temperature and pressure conditions evaluation of NiFeP/Zn-coated electrodes for alkaline water splitting

• Nifep/Zn coatings with high catalytic response were successfully synthetized. • High temperature and pressure conditions increase the catalytic response. • NiFeP/Zn catalytic coatings display bifunctional response to water splitting. The current transition to renewable energies has motivated research into energy storage using various techniques. Of these, electrolysis for pure hydrogen production stands out, as hydrogen is a crucial energy vector molecule capable of decarbonizing multiple sectors. However, the low efficiency of the electrolysis process presents a major limitation. In this work, an electrochemical evaluation of catalyst materials for water splitting under elevated temperature and pressure (ETP) conditions to replicate realistic electrolyzer operating environments is proposed. The NiFeP/Zn-coated nickel foam electrodes demonstrated a brain-like compact morphology, with EDS revealing a composition of 62.20 at% Ni, 13.90 at% Fe, 1.60 at% Zn, 7.65 at% P, and 15.21 at% O 2 . Electrochemical performance tests revealed a significant reduction in overpotential for the hydrogen evolution reaction (HER), achieving 38 mV at 8 bar and 80 °C, while the oxygen evolution reaction (OER) exhibited 119 mV at 1 bar and 80 °C, both at |30| mAcm −2 . Chronopotentiometry confirmed the stability of the coating for over 24 h at high current density of |400| mAcm −2 . The bifunctional capability of the coating was validated in a full-cell test, obtaining a remarkably low overpotential of 1.47 V at 30 mAcm −2 for overall water splitting under 80 °C and 8 bar conditions.