Tuning d-band electronic structure of Ni-Fe oxyhydroxides via doping engineering boosts seawater oxidation performance

Abstract

Seawater electrolysis holds significant importance for advancing clean energy conversion. NiFe-based catalysts exhibit outstanding performance in the oxygen evolution reaction (OER) under alkaline conditions. However, the instability of the Fe active center leads to leakage issues, hindering further development in the field of seawater electrolysis. Here, we adopt an element doping engineering strategy to enhance the OER activity of Ni-Fe oxyhydroxides and greatly stabilize the Fe sites by meticulously optimizing the d-band centers. Among the selected metals (Al, Ce, Co, Cr, Cu, Mn, Sn, Zn and Zr), Mn doping is the most effective as confirmed by both theoretical calculations and experimental verifications. The NiFeMn-OOH/NF formed in situ from the corresponding metal-organic framework requires only 217 mV to achieve a current density of 10 mA·cm^–2 in alkaline seawater, and exhibits exceptional stability. Theoretical calculations uncover that the Fe sites exhibit better balance of adsorption-desorption kinetics for OER intermediates than Ni sites and Ni-Fe dual-sites, while Mn sites with the polyvalent nature modulate the d-band center closer to Fermi level, facilitate the transfer of electrons across the catalyst surface, thus accelerating the reaction kinetics. This work is of considerable significance for achieving efficient and sustainable seawater electrolysis.