Tailoring Atomically Local Electric Field of Nife Layered Double Hydroxides with Ag Dopants to Boost Oxygen Evolution Kinetics

Abstract

The need for new clean energy sources has led to increased attention towards advanced electrochemical systems. However, the sluggish kinetics of the oxygen evolution reaction (OER) is one of the bottlenecks to determine the energy conversion efficiency, especially for water splitting. In this work, Ag ions are simultaneously introduced during the formation of the NiFe-LDH lattice, getting an oxygen vacancies (Vo) rich NiFeAg-LDH nanoclusters grown on carbon cloth (Vo-NiFeAg-LDH/CC) as the self-supporting anode material. The OER performance of Vo-NiFeAg-LDH/CC has been remarkably enhanced through Ag and Vo co-modification, with a low Tafel slope of 49.7 mV dec-1 in 1 M KOH solution. Additionally, the current density of Vo-NiFeAg-LDH/CC is 3.23 times than that of IrO2 at 2 V under alkaline flow electrolyzer. Theoretical calculations and experimental results together prove that the Ag and Vo strengthen the O* adsorption by enriching the electron density around the active sites, further promoting the deprotonation step from OH* to O* and accelerating the catalytic reaction. In a word, this work clarifies the structural correlation and synergistic mechanism of Ag dopant and Vo, which would give valuable insights for designing renewable energy-related catalysts in a more rational way.

Keywords: water splitting, Oxygen evolution reaction, NiFe-LDH, Ag dopants, oxygen vacancies