Hollow carbon nanoreactors integrating NiFe-LDH nanodots with adjacent La single atoms for efficient oxygen electrocatalytic reactions

Abstract

Optimizing both mass transport and electronic structure of the active component is of interest to obtain electrocatalysts with superior oxygen evolution reaction (OER) performance. Here, we miniaturized the classical NiFe-layered double hydroxides (NiFe-LDHs) and integrated them into S/N co-doped hollow hierarchical porous carbon (SNHPC) loaded with rare earth La single atoms (La SAs) to obtain nanoreactors. The unique carbon framework induced uniform deposition of LDH nanodots and ensured adequate exposure during electrocatalysis. The advantages of the carbon carrier for the local electric field and interfacial OH⁻ layer density in the catalytic process were confirmed by finite element simulations. The well-designed NiFe-LDH@La SNHPC exhibited satisfactory activity (overpotential of 251 mV at 10 mA cm⁻²) and stability in alkaline media, exceeding those of commercial RuO₂. Impressively, a cathode catalyst combining NiFe-LDH@La SNHPC with Pt/C can be stabilized in rechargeable zinc–air batteries (ZABs) for more than 350 h. Theoretical calculations indicated that the introduction of La SAs modified the electronic structures of the NiFe-LDH nanodots, activated lattice oxygen activity, optimized the adsorption strength of the intermediates, and reduced rate-determining step energy barriers in OER. This study provides guidance for the preparation and design of sub-microreactors and information on the strong electron interaction effects induced by rare earth species.