Effect of TiO₂ on electrocatalytic behavior of Ni-Mo alloy coating for hydrogen energy

Ni-Mo-TiO₂ composite coating has been developed through electrodeposition method by depositing titanium dioxide (TiO₂) nanoparticles parallel to the process of Ni-Mo alloy coating. The experimental results explaining the increased electrocatalytic activity of Ni-Mo alloy coating on incorporation of TiO₂ nanoparticles into its alloy matrix is reported here. The effect of addition of TiO₂ on composition, morphology and phase structure of TiO₂ – composite coating is studied with special emphasis on its electrocatalytic activity for hydrogen evolution reaction (HER) in 1.0 M KOH solution. The electrocatalytic activity of alloy coatings were validated using cyclic voltammetry (CV) and chronopotentiometry (CP) techniques. Under optimal condition, TiO₂ – composite alloy coating represented as (Ni-Mo-TiO₂)_{2.0 A dm⁻²} is found to exhibit the highest electrocatalytic activity for HER compared to its binary alloy counterpart. The increased electrocatalytic activity of (Ni-Mo-TiO₂)_{2.0 A dm⁻²} composite coating was attributed to the increased Mo content, porosity and roughness of coating, affected due to addition of TiO₂ nanoparticles, supported by SEM, EDX, XRD and AFM study. The increased electrocatalytic activity of (Ni-Mo-TiO₂)_{2.0 A dm⁻²} coating was found due to decreased R_ct and increased C_dl values, demonstrated by EIS study. Better electrocatalytic activity of (Ni-Mo-TiO₂)_{2.0 A dm⁻²} coating, compared to (Ni-Mo)_{2.0 A dm⁻²} coating has been explained through mechanism. Experimental study revealed that (Ni-Mo-TiO₂)_{2.0 A dm⁻²} composite coating follows Volmer-Heyrovsky mechanism, compared to Tafel mechanism in case of (Ni-Mo-TiO₂)_{2.0 A dm⁻²} coating, assessed on the basis of Tafel slopes.