Stabilization of layered lithium-rich manganese oxide for anion exchange membrane fuel cells and water electrolysers

The design of materials that efficiently catalyse the electrochemical reaction of molecular oxygen to hydroxide ions is key to the development of electrochemical devices. Here we demonstrate an approach to control the orbital hybridization of 3d and 4d/5d metals to tune the adsorption strength and stabilize the catalytic sites in the platinum-free catalysts Li2Mn1−xRuxO3. We show that in these materials, the stabilization of O 2p holes by changing the M–O covalency (M = 4d/5d metal) can help to mitigate structural instability. Operando X-ray absorption spectroscopy revealed that the Mn and Ru atoms are the active sites for the oxygen reduction reaction (ORR) and exhibit a high ORR activity with noteworthy stability compared with the Pt/C catalyst and outperform NiFe layered double hydroxides and RuO2 in the oxygen evolution reaction. Notably, Li2Mn0.85Ru0.15O3 shows a high power density of 1.2 W cm−2 and current density of 1.2 A cm−2 at 1.9 V in the anion exchange membrane fuel cell and water electrolyser, respectively. The development of superior and cost-effective catalysts for the oxygen reduction and evolution reactions is pivotal for the future hydrogen economy. Now a series of Ru-modified Li2MnO3 catalysts have been designed to optimize the electronic structure and achieve a high performance in both oxygen reduction and evolution reactions, as demonstrated in practical anion exchange membrane fuel cell and water electrolyser tests.