Low-Overpotential Hydrogen Evolution Reaction Electrode Loaded with Very Small Amounts of PtPd Alloy Nanoparticles

A methodology to prepare a stable, PtPd alloy-based electrode for the hydrogen evolution reaction (HER) is reported. The Pt/Pd mole ratio was 3.62. This electrode uses a stainless steel (SS) plate as the conducting substrate, which happens to have highly interconnected microtrenches on the surface. The area covered by the microtrenches corresponded to only 28% of the total surface area of the SS plate. An amorphous ultrathin (<50 nm) inorganic titanosilica binder was selectively coated only onto the interiors of the microtrenches, and 2–6 nm-sized PtPd alloy nanoparticles were finely dispersed into the amorphous layer. Thus, this HER electrode represents the first example to show that only a minor portion (28%) of the conducting substrate was intentionally made to be active. Furthermore, the amounts of Pt and Pd were very small, being only 2.06 and 0.31 μg cm^–2, or 10.6 and 2.9 nmol, respectively, of the whole substrate. Despite that only 28% of the whole surface was covered by the active sites and the loaded amounts of Pt and Pd per 1 cm² were very small, the measured HER overpotentials were much lower than those of the reported Pt-based HER electrodes, including 20% Pt supported on glassy carbon (Pt/C), in the current density region between 0.1 and 1 A cm^–2, regardless of the pH of the electrolyte solution. Loading of very small amounts of Pt (0.5–2.09 μg cm^–2) on HER electrodes has also been demonstrated in the literature. However, their observed HER overpotentials were much higher than those we observed. Thus, this work demonstrates a novel direction for the preparation of low-cost HER electrodes, yet with very low overpotentials by coating only a minor portion (28%) of the conducting substrate with very small amounts of PtPd alloy nanoparticles.