Cooperative d-electron density regulation on layered double hydroxides for boosting overall water/seawater splitting

NiFe layered double hydroxide (NiFe LDH) has emerged as a promising catalyst for the oxygen evolution reaction (OER); however, its hydrogen evolution reaction (HER) activity remains suboptimal due to unfavorable electronic structures, particularly the d-electron density of metal sites, which impede water dissociation and lead to poor hydrogen adsorption/desorption capabilities. Herein, we introduce an efficient cooperative d-electron density regulation (CDDR) engineering to comprehensively optimize the d-electron density of NiFe LDH by grafting MoOx-modified NiFe LDH nanosheets onto porous nickel particles (PNPs). The PNPs facilitate d-electron density modulation along the edges of the nanosheets, while the MoOx species enable d-electron density modulation across the plane of the nanosheets, thus cooperatively constructing enriched d-electron density in NiFe LDH. Theoretical studies validate the CDDR process and reveal that the enriched d-electron density accelerates water dissociation and optimizes the hydrogen adsorption behavior of NiFe LDH. As a result, the engineered catalyst exhibits significantly improved HER activity, achieving an ultra-low overpotential of 38 mV at 10 mA cm−2 in 1 M KOH. Additionally, the CDDR-optimized catalyst also exhibits good OER performance, demonstrating excellent bifunctional performance for overall water splitting in both alkaline freshwater and seawater electrolytes. This work presents a novel CDDR strategy for engineering NiFe LDH into efficient HER catalysts without compromising its OER activity, potentially paving the way for the development of active and robust electrocatalysts for sustainable energy applications.