Constructing the Built-In Electric Field in Atomic Mn–O–Co Heterointerfaces for the Oxygen Evolution Reaction in Acidic Water Electrolysis

For improving the activity of low-cost non-noble metal catalysts for the oxygen evolution reaction (OER) in acidic water electrolysis, a strategy was proposed to construct atomic Mn–O–Co asymmetric units within Co 3 O 4 to form a directional built-in electric field. Mn-doped Co 3 O 4 catalysts (Mn x Co 3– x O 4 ) were synthesized via a hydrothermal-calcination method. The computational results indicated that Mn selectively occupied the octahedral Co site, forming a directional electron transfer pathway from Mn to Co, which effectively modulated the electronic structure of both Co and O. In situ Raman spectroscopy proved that the Mn–O–Co structure accelerated the efficient conversion of oxygen-containing intermediates. DFT calculations indicated that the Mn–O–Co directional built-in electric field facilitated H 2 O polarization via enhancing hydrogen bonding and, by optimizing the *OOH adsorption structure, lowered the OER rate-determining step barrier by 0.05 eV. The asymmetric Mn–O–Co coordination structure lowered the p-band center of the O atom by ∼0.1 eV atom, which passivated lattice-O to improve lattice stability. XPS revealed that the Mn 0.6 Co 2.4 O 4 material had the maximum built-in potential. The electrochemical testing indicated that it exhibited an overpotential of only 243 mV at a current density of 10 mA cm –2 and maintained stability for over 80 h.