BiOI/CoMoO ₄ Heterostructure as an Effective Bifunctional Nanometer-Sized Electrocatalyst for Water Splitting

Electrochemical water splitting is a sustainable method for hydrogen generation. The development of highly efficient, durable, and cost-effective bifunctional electrocatalysts remains a scientific and technological challenge. Herein, we propose a strategy for fabricating hybrid materials composed of bismuth oxyiodide (BiOI) decorated with cobalt molybdate (CoMoO 4 ). BiOI/CMO nanocatalysts were synthesized using an environmentally friendly, solvent-free, mechanochemical milling method. The nanomaterial characterization of the synthesized catalyst was investigated using XRD, SEM, HR-TEM, XPS, and electrochemical measurements. The electrocatalytic performance of nanometer-sized materials for BiOI, CMO, and BiOI/CMO catalysts in hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), including cyclic voltammetry (CV), electrochemical double-layer capacitance ( C dl ), linear sweep voltammetry (LSV), Tafel analysis, electrochemical impedance spectroscopy (EIS), and chronoamperometry under a 3 M KOH alkaline environment. A BiOI/CMO heterostructure exhibited extremely low overpotentials of 111 and 206 mV for HER and OER at a current density of 10 mA cm –2, with Tafel slopes of 135 and 139 mV dec –1, respectively. That heterostructure exhibited outstanding stability for 70 h continuously, confirming its feasibility for sustainable hydrogen production. DFT studies indicate a decreased energy barrier for water splitting, a near-thermoneutral condition for effective hydrogen evolution reaction (HER), and optimized adsorption of intermediates for oxygen evolution reaction (OER). The increased density of states next to the Fermi level further facilitates charge transfer, corroborating the enhanced catalytic rates at the heterointerface. Therefore, Bibased/CoMoO 4 nanocomposites are ideal for an enhanced water-splitting performance.