Simple cathodic deposition of FeS/NiS-activated Ni/NiO heterojunctions for high-concentration overall water splitting reactions

To produce hydrogen through electrolysis of water, the creation of effective and affordable electrodes for overall water splitting is essential. We present the deposition of active oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) components on the same NF in this work, enabling the synergistic effect of FeS/NiS and Ni/NiO active components for effective overall water splitting. In alkaline electrolytes, NiFe@NF electrodes deposited using a straightforward two-step cathodic deposition process at various currents exhibit good catalytic activity for both OERs and HERs. For the electrode to be stable over time, Ni/NiO is firmly bonded to NF, and the specific surface areas of the FeS/NiS nanoflowers provide efficient electron transport. The electrode outperformed the RuO2 electrode by achieving a current density of 10 mA cm−2 at an OER overpotential of 168 mV. Additionally, the HER only needs a 84 mV overpotential to reach a current density of 10 mA cm−2. In addition, an electrolytic cell constructed with the same NiFe@NF as the cathode and anode requires a cell voltage of only 1.47 V to achieve a current density of 10 mA cm−2. It can operate stably for a long time (120 h) at high temperature and high concentration conditions. This work highlights the importance of active components with simultaneous OER and HER activities on electrodes for efficient catalytic applications in overall water splitting.