Modulating the bimetallic ratio of amorphous nickel-manganese MBenes for direct seawater electrolysis

Direct seawater electrolysis for green hydrogen production offers a sustainable solution to decarbonize the energy sector without depleting freshwater resources. However, designing efficient electrocatalysts for this process remains challenging. Various physicochemical properties, such as chemical composition, surface chemistry, roughness, and intrinsic resistivity, can impact performance, but they are not fully understood. This study explores how the electrocatalytic activity of amorphous NiMn MBenes in alkaline water, saline water, and seawater can be optimized by adjusting the bimetallic ratio during synthesis. The results show that surface chemistry is the dominant factor influencing electrocatalytic activity. The Ni-rich NiMn MBene exhibits the highest electrochemical surface area (ECSA), charge distribution (CdL), and favourable adsorption of active intermediates, leading to the best electrocatalytic performance. Specifically, achieving a hydrogen evolution reaction (HER) overpotential of −0.28/-0.04/-0.03 V at −10 mA cm−2 and an oxygen evolution reaction (OER) overpotential of 0.36/0.44/0.25 V at 10 mA cm−2 in alkaline water/alkaline saline water/alkaline natural seawater, respectively. These findings provide valuable insights into the design and surface engineering of bimetallic MBenes for efficient direct seawater electrolysis.