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

Abstract

The sulfion oxidation reaction (SOR) could offer an energy-efficient and tech-economically favorable alternative to the oxygen evolution reaction (OER) for H2 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-S2- d-p orbit coupling. Herein, we propose a feasible strategy of screening direct d-p orbit hybridization between TM and S2- by constructing the Turing structure composed of lamellar stacking carbon-confined nickel nanosheets. The optimized p-p orbit coupling between electron-injected carbon and S2- enables exceptional catalytic activity and stability for sulfion degradation and energy-efficient yet value-added H2 production. Specifically, it achieves a current density of 500 mA cm-2 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 Acm-2 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 kgh-1m-2 for sulfur and H2, respectively.