Revealing the role of 1T- & 2H- molybdenum Disulfide/Nickel sulfide heterojunction for efficient overall water splitting.

In the ongoing quest for cost-effective and durable electrocatalysts for hydrogen production-a critical element of sustainable energy transformation-the 1T phase of Molybdenum Disulfide (MoS) faces challenges due to its thermodynamic instability and the trade-off between efficiency and durability. Conversely, the 2H phase of MoS, often disregarded in favor of the metallic 1T phase, suffers from its inert nature and limited active sites. To overcome these limitations, this study employs a straightforward hydrothermal synthesis strategy that couples both 1T and 2H phases of MoS with NiS, forming 1T- and 2H- MoS/NiS heterojunctions. Enhanced by NiS's abundant active sites, improved electron transport capabilities, synergistic interface effects, and better structural stability, these heterojunctions achieve a high current density exceeding 500 mA cm at low overpotentials, along with prolonged durability for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline electrolytes. Remarkably, an electrolyzer assembly utilizing 1T-MoS/NiS as the cathode and 2H-MoS/NiS as the anode demonstrates a competitive voltage of 1.58 V at 20 mA cm, showcasing superior performance in overall water splitting compared to other non-noble metal-based electrocatalysts. This study not only offers a viable method for synthesizing efficient and stable electrocatalysts for water splitting using transition metal-based heterogeneous structures but also addresses the fundamental challenges associated with 1T and 2H phases of MoS.