Electronic Structure Modulation of Palladium by Nickel Doping for Highly Efficient Hydrogen Evolution in Acidic Media

Developing cost-effective and highly active electrocatalysts for the hydrogen evolution reaction (HER) in acidic media is crucial for sustainable hydrogen production. While palladium (Pd) is a promising alternative to platinum (Pt), its performance is often limited by its overly strong hydrogen binding energy. Herein, we report a strategy to modulate the electronic structure of Pd by doping it with nickel (Ni) to create ultrasmall PdNi alloy nanoparticles supported on carbon nanotubes (PdNi/CNT). The optimized catalyst, PdNi(H)/CNT, demonstrates exceptional HER performance, achieving a low overpotential of just 15.6 mV at a current density of −10 mA cm–2 and a small Tafel slope of 35.0 mV dec–1. This activity surpasses that of both monometallic Pd/CNT and the commercial 20 wt % Pt/C benchmark. Furthermore, the catalyst exhibits outstanding long-term stability for over 50 h. A combination of experimental characterization and density functional theory (DFT) calculations reveals that Ni doping effectively donates electrons to Pd, which optimizes the electronic environment of the Pd active sites. This electronic modulation weakens the hydrogen adsorption, resulting in a near-thermoneutral Gibbs free energy of hydrogen adsorption (ΔGH*) of −0.02 eV. This work provides a clear pathway for enhancing the intrinsic activity of Pd-based catalysts by tuning their electronic structure through alloying.