Dynamic Decoupling of Pt─H Intermediates Formation From Water Dissociation for Efficient Alkaline Hydrogen Evolution.

The formation of metal-hydrogen intermediates (M─H*) is critical for the alkaline hydrogen evolution reaction (HER), but is kinetically hindered by the energy-intensive water dissociation. Here, we report a distinct pathway in the model catalyst of Pt nanoparticles loaded on TiH1.924 (Pt/TiH1.924), which directly generates Pt─H* by transferring lattice hydrogen from TiH1.924 to Pt catalytic sites, while the lattice hydrogen can be dynamically replenished by the electrolyte spontaneously. This pathway decouples Pt─H* formation from water dissociation at a significantly lower energy barrier, as evidenced by operando differential electrochemical mass spectrometry and in situ Raman spectroscopy. The continuous hydrogen supply from the hydride support enables the Pt/TiH1.924 catalyst to achieve a 35.6-fold higher mass activity than Pt/C at 100 mV overpotential. Moreover, in an anion exchange membrane water electrolyzer with Pt/TiH1.924 as the cathode, the cell voltage only requires 1.76 V at a current density of 1 A cm⁻², and the device can operate stably for over 1000 h under this current density. This work proposes a lattice hydrogen-mediated mechanism to boost alkaline HER and other electrochemical processes constrained by slow M─H* formation, by decoupling Pt─H* production from water dissociation using metal hydride supports.