Dual roles derived from lattice incorporation of Cl- in ultrathin LiCoO2-xClx for water elelctrolysis

Abstract

LiCoO2 is a kind of promising electrocatalyst for oxygen evolution reaction (OER), while it is difficult to successfully achieve the nanosheets morphology of LiCoO2 with regulated electronic configuration and optimal reaction pathway. Here, we demonstrate that doping Cl ion into the lattice of LiCoO2-xClx ultrathin nanosheets by alkaline molten salt method can bring out dual roles, which not only adjust the covalency of Co-O bond to improve OER activity, but also promote the leaching of Li to activate lattice oxygen. The deep delithiation of LiCoO2-xClx to produce O22– intermediates is inclined to be lattice oxygen mediated mechanism (LOM). The more oxygen vacancies due to the accurate lattice doping of optimized Cl- regulate the coordination environment and electron distribution of Co sites. The electrochemical measurements show that the overpotential of LiCoO2-xClx at 10 mA cm−2 for OER is reduced by 130 mV compared to LiCoO2 by solid phase synthesized. Additionally, the lattice doping of Cl- can make the current density increase from 7.55 to 26.88 A g−1 at 2.0 V in Anion-exchange membrane water electrolyzer (AEMWE). The dual regulation strategy based on lattice doping of halogen ions provides a new viewpoint by adjusting coordination environment and optimizing reaction path for OER.