Study on the Catalytic Activity and Selectivity of Manganese Dioxide-Modified Nickel–Iron-Based Hydroxide Electrodes for Initiating the Oxygen Evolution Reaction in Natural Seawater

Transition metal oxides, particularly NiFe(OH)2, are recognized for their high oxygen evolution reaction (OER) activity and structural stability. However, their performance in natural seawater electrolysis remains insufficiently studied. Manganese dioxide (MnO2), which is known for its multiple crystal phases and high OER selectivity, can be incorporated to enhance the catalytic properties. In this study, the OER catalytic performance of carbon cloth-supported manganese dioxide-modified nickel–iron bimetallic hydroxide (MnO2-NiFe-LDH/CC) electrodes was explored in both alkaline and natural seawater. Electrochemical tests demonstrated that the MnO2-NiFe-LDH/CC electrode achieved overpotentials of 284 mV and 363 mV at current densities of 10 mA·cm−2 and 100 mA·cm−2, respectively, with a Tafel slope of 68.6 mV·dec−1 in alkaline seawater. Most importantly, the prepared MnO2-NiFe-LDH/CC electrode maintained stable OER performance over 120 h of testing. In natural seawater, the MnO2-NiFe-LDH/CC electrode outperformed the NiFe-LDH/CC electrode by exhibiting an oxygen evolution selectivity of 61.1%. This study highlights the potential of MnO2-modified nickel–iron-based materials for efficient and stable OER in seawater electrolysis, which offers a promising approach for sustainable hydrogen production in coastal desert regions.