Theoretical and experimental studies of 2,2-bipyridine for nanocrystalline zinc-nickel deposition

A nanocrystalline Zn-Ni alloy with an average grain size of 25 nm was electrodeposited from an alkaline bath with 2,2-bipyridine. An effective approach using electrochemical experiments and quantum chemical calculations was employed to investigate the effect of 2,2-bipyridine on the process of Zn-Ni deposition. Quantum chemical calculations indicate that the ring structure (especially nitrogen atoms) in 2,2-bipyridine is the most active reactive site for its adsorption. 2,2-bipyridine can form effective and stable surface adsorption on the electrode surface by sharing electrons between the ring structure and Zn-Ni atoms. The addition of 2,2-bipyridine does not change the single-step two-electron transfer mechanism with the diffusion-controlled process of Zn-Ni growth. However, better corrosion resistance and wear resistance of nanocrystalline Zn-Ni alloys is obtained with 2,2-bipyridine, which can be associated with the rapid formation of hydrophobic nature on nanocrystalline Zn-Ni alloys, and its smoother surface as well as higher hardness and lower friction coefficient, respectively.