Binder free cobalt iron phosphate thin films as efficient electrocatalysts for overall water splitting

Designing nanostructure based robust catalyst for the electrochemical water splitting is the great task in the energy conversion field to accomplish high electrical conductivity, low overpotential and long lasting activity. Herein, the electrochemical overall water splitting is reported by using the hydrothermally synthesized binder free cobalt iron phosphate thin films on low cost stainless steel substrates as a conducting backbone for the first time. The effect of composition ratio variation of cobalt and iron was studied on the structural, compositional, morphological, and surface electronic properties by conducting various characterizations which results in amorphous hydrous cobalt iron phosphate having mesoporosity. The as synthesized cobalt iron phosphate having composition ratio (50:50 of Co:Fe) exhibits excellent electrochemical OER and HER catalytic water splitting performance. Best performing electrode exhibits smallest overpotentials of 251.9 mV and 55.5 mV for OER and HER respectively at 10 mA/cm² current density. To split water molecule into the H₂ and O₂ by overall water splitting in same alkaline medium, the potential of 1.75 V was required after long duration (100 h) catalysis. Overall analysis confirms the cobalt iron phosphate thin films are outstanding and robust for the hydrogen production as clean renewable energy source.