Ultrafast and durable seawater hydrogen evolution driven by hydrogen spillover on PtCoNi@MoO3 nanowires

Direct seawater electrolysis holds prospect for sustainable H 2 production, yet its practical application is impeded by slow hydrogen evolution reaction (HER) kinetics and severe chloride-induced corrosion of electrocatalysts. To address these challenges, we present a PtCoNi@MoO 3 core-shell heterostructure designed to strategically segregate the elementary HER steps via a hydrogen spillover mechanism. The crystalline PtCoNi alloy core facilitates water dissociation, generating adsorbed hydrogen (H*). These H* intermediates subsequently spill over to the amorphous MoO 3 shell, where near-thermoneutral binding energies promote rapid H 2 recombination. This bifunctional design delivers exceptional HER activity in alkaline seawater, requiring only 23 mV overpotential at 10 mA cm −2 and only 70 mV to reach an industrial-scale 100 mA cm −2 . The evolving Tafel slope, from 43.0 mV dec −1 (10 mA cm −2 ) to 82.2 mV dec −1 (100 mA cm −2 ), highlights a dynamic shift in the rate-determining step. Density functional theory (DFT) calculations confirm a minimal kinetic barrier for H* spillover from PtCoNi to MoO 3 . Furthermore, the MoO 3 shell provides a physicochemical barrier, inhibiting Cl − adsorption that effectively passivates the active core against corrosion. This protection leads to outstanding stability, demonstrated by continuous operation for over 300 h at 100 mA cm −2 . This research presents a mechanism-driven strategy, leveraging interfacial hydrogen spillover, to design robust and chloride-tolerant catalysts for high performance seawater electrolysis. • Core-shell structure overcomes the activity-stability trade-off • Hydrogen spillover spatially decouples HER elementary steps • Amorphous MoO 3 shell provides robust chloride tolerance • Catalyst achieves industrial-scale currents at low overpotential • Exceptional durability demonstrated in 300-h continuous operation