Ligand-Induced Room Temperature Synthesis of NiCoSe Nanostructures: Highly Efficient Electrocatalyst for Hydrazine-Assisted Hydrogen Production

Transition metal selenides are considered as promising electrode materials to catalyze various electrocatalytic reactions. The synthesis of these metal selenides involves harsh synthetic conditions and multistep routes. Herein, a room-temperature ligand-assisted strategy has been developed to synthesize NiSe, CoSe, and NiCoSe in pure phase. This study delves into the significant impact of ligands on nanoparticle synthesis, with a particular focus on their pivotal role in finely adjusting the crystalline phase of resulting nanomaterials. We have focused on identifying the specific ligands that can effectively manipulate nucleation and growth processes for the synthesis of specific crystal structures of MSe (M-Ni, Co). The role of functional groups in ligands was probed, and it was found that carboxylic acid groups played a key role in facilitating the synthesis of pure phase NiSe, CoSe, and NiCoSe. Through a detailed examination of existing literature and theoretical calculations, we have investigated the mechanism and role of carboxylate ligands in MSe (M-Ni, Co) formation. Computational investigations suggest the formation of a metastable metal-carboxylate intermediate complex optimizes the reaction condition, makes it more favorable for re-orientation, and allows selenium to approach the nickel center. Furthermore, the synthesis of NiCoSe aimed to enhance the electrocatalytic performance of NiSe and CoSe, as the bimetallic (NiCoSe) material exhibits superior electrochemical properties compared to their monometallic counterparts. The electrocatalytic activities of the synthesized transition metal selenides were evaluated for hydrazine-assisted water splitting. Bimetallic NiCoSe displayed superior electrocatalytic performance toward hydrazine oxidation and hydrogen evolution reaction compared to monometallic phases of NiSe and CoSe. The bimetallic component required a potential of 0.20 (V) vs. RHE and an overpotential of 0.20 V to attain 10 mA/cm2 for HzOR and HER, respectively. Moreover, NiCoSe displayed excellent activity as a bifunctional catalyst, and it required a very low cell voltage of 0.45 V to attain a current density of 10 mA/cm2 for H2 production. The free energy profile of the stepwise HzOR has been investigated in detail. The computational results reveal an enhanced feasibility of HzOR on the NiCoSe (1:1) compared to NiSe. Therefore, concisely, this work offers an innovative synthesis protocol for the ligand-induced room temperature synthesis of transition metal selenide nanostructures and their application for hydrazine-assisted hydrogen production.