Sustainable and Cyclic Synthesis of 2D Co(OH)₂ Nanosheets for Scalable Production of High-Performance Electrocatalysts

Ultrathin 2D nanomaterials with extremely large surface area and unique electrochemical properties are considered excellent electrocatalyst candidates for clean energy conversion and environmental applications. However, it is still challenging to prepare 2D catalysts through a scalable and sustainable process that may become suitable for industrial demands. Here, we reported a facile cyclic synthesis method of ultrathin 2D nanomaterials based on the ionic layer epitaxy. By repeatedly refreshing a surfactant monolayer on the solution surface, free-standing 2.2 nm thick hexagonal Co(OH)₂ nanosheets were obtained from the water surface at ambient conditions in multiple cycles. These nanosheets exhibited a consistently high OER performance with an average overpotential of 427.4 ± 5.3 mV at 10 mA cm⁻². Remarkably, hexagonal NSs could be obtained from a wide range of precursor concentrations which could enable over 84 cycles of synthesis on the same stock precursor solution. It will shed light on the design of autonomous and sustainable synthesis of 2D nanomaterials for advanced electrocatalysis development toward a clean future.