Abstract
Developing ultraefficient electrocatalytic materials for the hydrogen evolution reaction (HER) with low content of expensive platinum group metals (PGMs)
via
low-energy-input procedures is the key to the successful commercialization of green water electrolysis technologies for sustainable production of high-purity hydrogen. In this study, we report a facile room-temperature synthesis of ultrafine metallic Ir nanoparticles on conductive, proton-intercalated TiO
2
nanotube (H-TNT) arrays
via
galvanic displacement. A series of experiments demonstrate that a controlled transformation of the H-TNT surface microstructure from neat open-top tubes to disordered nanostripe bundles (“nanograss”) is highly beneficial for providing an abundance of exposed Ir active sites. Consequently, for nanograss-engineered composites, outstanding HER activity metrics are achieved even at very low Ir(
iii
) precursor concentrations. An optimum Ir@TNT cathode loaded with 5.7 μg
Ir
cm
−2
exhibits an overpotential of −63 mV at −100 mA cm
−2
and a mass activity of 34 A mg
Ir
−1
at −80 mV under acidic conditions, along with excellent catalytic durability and structural integrity. Density functional theory (DFT) simulations reveal that the hydrogen-rich TiO
2
surface not only stabilizes the deposited Ir and weakens its H binding strength to a moderate intensity, but also actively takes part in the HER mechanism by refreshing the Ir catalytic sites near the Ir|H–TiO
2
interface, thus substantially promoting H
2
generation. The comprehensive characterization combined with theory provides an in-depth understanding of the electrocatalytic behavior of H-TNT supported PGM nanoparticles and demonstrates their high potential as competitive electrocatalyst systems for the HER.