Post-Synthetic Treatment of Nickel-Iron Layered Double Hydroxides for the Optimum Catalysis of the Oxygen Evolution Reaction

TL;DR

This study develops post-synthetic treatments to optimize NiFe LDH catalysts for oxygen evolution, achieving record low overpotentials and enhanced long-term stability by controlling particle size and edge-site density.

Contribution

It introduces a novel post-synthetic treatment method to control NiFe LDH particle size and edge-site density, significantly improving OER catalytic performance.

Findings

Achieved OER overpotential of 237 mV with size-reduced NiFe LDH/SWCNT composites.

Enhanced long-term catalytic activity under operational conditions.

Demonstrated that post-synthetic size control surpasses previous synthetic approaches.

Abstract

Nickel-iron layered double hydroxide (NiFe LDH) platelets with high morphological regularity and sub-micrometre lateral dimensions were synthesized using a homogeneous precipitation technique for highly efficient catalysis of the oxygen evolution reaction (OER). Considering edge sites are the point of activity, efforts were made to control platelet size within the synthesized dispersions. The goal is to controllably isolate and characterize size-reduced NiFe LDH particles. Synthetic approaches for size control of NiFe LDH platelets have not been transferable based on published work with other LDH materials and for that reason, we instead use post-synthetic treatment techniques to improve edge-site density. In the end, size reduced NiFe LDH/single-wall carbon nanotube (SWCNT) composites allowed to further reduce the OER overpotential to 237 plus/minus 7 mV ( L = 0.16 plus/minus 0.01 micrometres, 20 wt% SWCNT), which is one of the best values reported to date. This approach as well improved the long term activity of the catalyst in operating conditions.