Defect Engineering of a d-p Orbital Hybridized Osmium/o-CNTs Heteroelectrocatalyst with an Optimized Interfacial Water Structure for Hydrogen Evolution within an Al | OH– | H2 Primary Cell

Abstract Developing efficient and durable electrocatalysts for alkaline seawater hydrogen evolution remains challenging because of sluggish water dissociation kinetics. Herein, we report a defect-rich d-p orbital-hybridized Os/o-CNTs electrocatalyst (dph-Osdef/o-CNTs) prepared by rapid room-temperature NaBH4 reduction. The partially oxidized CNT support anchors defective Os nanoclusters and induces C–Os/C–O–Os electronic coupling, generating electron-deficient Os sites with modulated 5d electronic structures. In alkaline simulated seawater (1 M NaOH + 3.5 wt % NaCl), dph-Osdef/o-CNTs requires only 91 mV to reach 100 mA cm–2 and exhibits a Tafel slope of 19 mV dec–1, with stable operation over 350 h and 10,000 CV cycles. In situ Raman spectroscopy, AIMD simulations, and DFT calculations reveal that Os vacancies reorganize interfacial water into an ordered H-bond network, promote O-down water adsorption, and reduce the water dissociation barrier from 1.12 to 0.56 eV. Moreover, an Al | OH– | H2 primary cell using dph-Osdef/o-CNTs as the cathode delivers 1.41 V and 10.92 mW cm–2, enabling simultaneous hydrogen generation and electricity output.