Bioregulation of FeNi LDH morphology and electronic structure to highly promote electrocatalytic oxygen evolution

Abstract

NiFe-based layered double hydroxides (LDHs) are currently the most efficient oxygen evolution reaction (OER) catalysts in alkaline medium. However, their shortcomings such as insufficient electron transport ability, few exposed active sites and susceptibility to aggregation hindered their further development. In this paper, soluble extracellular polymer substances (s-EPS) modified by urea was used as biosurfactant and pH regulator, micro-morphology and electronic structure of FeNi LDH were accurately regulated to upgrade its stability, electrical conductivity, electrochemical active surface area and kinetic process. Tryptophan residue protein in EPS is mainly responsible for the interaction between s-EPS and FeNi LDH. Experimental and theoretical calculation results demonstrate that the introduction of s-EPS can coordinate the morphology and electron distribution of active centers, consequently optimizing the adsorption energy of reaction intermediates and enhancing the inherent catalytic activity for OER. As expected, s-EPS@FeNi LDH exhibited excellent OER performance under alkaline conditions, and only had an overpotential of 220 mV at a current density of 10 mA cm−2, which is superior to other promising FeNi-based catalysts. This work sheds light on realizing the efficient assembly of LDH and s-EPS, and provides a reliable method for the morphology and electronic structure modification of LDH for more efficient OER.