Screened d-p Orbital Hybridization in Turing Structure of Confined Nickel for Sulfion Oxidation Accelerated Hydrogen Production.

The sulfion oxidation reaction (SOR) could offer an energy-efficient and tech-economically favorable alternative to the oxygen evolution reaction (OER) for H production. Transition metal (TM) based catalysts have been considered promising candidates for SOR but suffer from limited activity due to the excessive bond strength from TM-S d-p orbit coupling. Herein, we propose a feasible strategy of screening direct d-p orbit hybridization between TM and S by constructing the Turing structure composed of lamellar stacking carbon-confined nickel nanosheets. The optimized p-p orbit coupling between electron-injected carbon and S enables exceptional catalytic activity and stability for sulfion degradation and energy-efficient yet value-added H production. Specifically, it achieves a current density of 500 mA cm at an ultralow potential of 0.67 V vs. RHE for alkaline SOR. Theoretical calculations indicate that the electron transfer from Ni imparts metallicity and a higher p-band center to carbon shells, thereby contributing to optimized p-p orbit hybridization and a thermodynamically favorable stepwise sulfion degradation. Practically, a two-electrode flow cell achieves an industrial current density of 1 A cm at an unprecedented low voltage of 0.91 V while maintaining stability for over 300 hours, and exhibits high productivities of 3.83 and 0.32 kg h m for sulfur and H, respectively.