Van der Waals Heterostructure via Spontaneous Self-Restacked Assembling for Enhanced Water Oxidation

The pursuit of sustainable energy solutions has identified water oxidation as a crucial reaction, with the oxygen evolution reaction (OER) serving as a decisive efficiency determinant in water-technologies. This study presents a novel van der Waals (vdW) heterostructure catalyst, synthesized through a spontaneous self-restacked of nickel-iron-based phosphorus-sulfur compounds (NiPS₃ and FePS₃). Density Functional Theory (DFT) calculations underpinned the thermodynamic spontaneity of the restacking process, uncovering a semiconductor-to-metallic electronic transition that significantly amplifies electrocatalytic functionality. The catalyst demonstrates a remarkable OER performance, achieving a low overpotential of 257 mV at 20 mA cm⁻², a Tafel slope of 49 mV dec⁻¹, and demonstrates remarkable durability sustaining 500 mA cm⁻² for 140 hours. In addition to its high performance, the material's rapid reconstruction facilitated by surface electron enrichment and the release of phosphate and sulfate during OER underscores a dual enhancement in both activity and stability. The universality of the synthesis method is further demonstrated by extending the approach to other MPS₃ materials (M = Mn, Co, Zn), establishing a generalized platform for developing high-performance OER catalysts. This work represents a significant advancement in the application of restacked vdW heterostructures as a foundation for advanced electrocatalytic materials.