Revitalizing Alkaline Hydrogen Evolution Reaction Performance of Co_0.85Se/MoSe₂ by Microstructural Engineering with Nonprecious Cobalt Oxalate

Alkaline hydrogen evolution reaction (HER) is challenging due to the additional energy barrier required for dissociating the H–OH bond in the Volmer step. However, synergistic coupling of an oxophilic Co-based material with MoSe2 enhances alkaline HER efficiency. So, this study delineates the synthesis of a unique nonstoichiometric Co0.85Se/MoSe2 composite as an effective catalytic network for alkaline HER. Employing an oxalate ligand-assisted wet-chemical technique followed by autoclaving, the composite structure was formed and confirmed through diligent physical characterization, demonstrating an interfacial network between Co0.85Se and MoSe2. The Co0.85Se/MoSe2 composite exhibits remarkable performance, requiring only 70 ± 3 and 140 ± 5 mV overpotentials to achieve current densities of −10 and −50 mA/cm2, respectively, in alkaline conditions. It also shows fast reaction kinetics with a Tafel slope of ∼70 ± 3 mV/dec, a high electrochemical active surface area, low charge-transfer resistance, and excellent electrochemical stability over 25 h in 1 M KOH. The enhanced activity is attributed to the synergistic coupling between Co0.85Se and MoSe2. Co0.85Se aids in dissociating the H–OH bond during the Volmer step, and MoSe2 facilitates the Heyrovsky step. Furthermore, the reallocation of local electron density from Co to Mo centers was found to be one of the major reasons for the enhanced activity. The study also highlights the importance of using CoC2O4·2H2O as a precursor for fabricating the Co0.85Se/MoSe2 electrocatalyst, showing superior results compared to composites prepared using Co(NO3)2·6H2O and Co3O4. The oxalate precursor enhances the exposure of catalytically active sites within the Co0.85Se/MoSe2 framework, maximizing both geometric and intrinsic activity. For overall water splitting, the CoC2O4·2H2O-derived Co0.85Se/MoSe2 and CoC2O4/Ag2C2O4 were used as the HER and OER catalysts, respectively, requiring only 1.6 V of cell potential to reach a 10 mA/cm2 current density and maintaining 72 h of prolonged stability in 1 M KOH.