Deciphering Doping Effects in a V-Doped Ni Catalyst for Hydrogen Electrooxidation.

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science

Background:

• Soluble metal-doped nickel (Ni) catalysts show improved performance in alkaline electrolytes for hydrogen oxidation reaction (HOR).
• The exact mechanism behind the enhanced performance, particularly the role of evolving surface structures, remains unclear.
• Understanding these mechanisms is crucial for designing efficient electrocatalysts.

Purpose of the Study:

• To investigate the intrinsic function of vanadium (V) species in enhancing HOR kinetics in V-doped Ni nanoparticles.
• To elucidate the role of V doping in modifying the electronic structure and surface properties of Ni catalysts.
• To explore the relationship between hydroxyl binding energy and catalytic activity.

Main Methods:

• Synthesis and characterization of V-doped Ni nanoparticles.
• Electrochemical evaluation of catalytic activity for HOR in alkaline media.
• Surface analysis to identify V species and their evolution during the reaction.
• Theoretical calculations (e.g., Density Functional Theory) to study binding energies.
• Alkali-metal cation probe experiments.

Main Results:

• V-doped Ni nanoparticles exhibited a mass-normalized kinetic current density over 12 times higher than undoped Ni.
• Surface V-species (oxides and doped atoms) dissolved during the alkaline HOR process.
• Internal V-dopants weakened the hydroxyl binding energy (OHBE) on Ni surfaces.
• Theoretical calculations and experiments confirmed Ni operates on the overstrong binding side of the HOR volcano plot.
• Weakening OHBE via V-doping shifted the activity towards the optimal volcanic apex.

Conclusions:

• Vanadium doping effectively enhances HOR kinetics in Ni catalysts by weakening hydroxyl binding energy.
• The beneficial effect of V is attributed to internal V-dopants that optimize the adsorption/desorption balance, rather than surface V species.
• This study provides a mechanistic understanding for designing advanced Ni-based electrocatalysts for HOR by tuning OHBE.