To enhance the activity and stability of acidic oxygen evolution reaction (OER), a heterostructure between Co₃O₄ and MnO₂ (Co₃O₄/MnO₂) was synthesized by a two-step thermal-decomposition method. In situ characterizations revealed that the transfer of electrons across the heterointerfaces enhances the faster lattice-oxygen-mediated mechanism (LOM) pathway, ultimately facilitating the acidic OER process.

Abstract

Designing and developing highly active and stable non-precious metal electrocatalysts for the acidic oxygen evolution reaction (OER) is a key issue in realizing the widespread application of proton exchange membrane water electrolyzers (PEMWEs). Spinel-type Co₃O₄ has been considered a potential candidate due to its competitive activity for acidic OER; however, its inferior stability hinders its practical deployment. On the other hand, MnO₂ has garnered significant attention due to its excellent resistance to dissolution and self-healing properties in acidic electrolytes. Therefore, we herein report to enhance the activity and stability of acidic OER by interfacial engineering to construct a heterostructure between Co₃O₄ and MnO₂ (Co₃O₄/MnO₂). As a result, Co₃O₄/MnO₂ exhibits efficient activity with a current density of 100 mA cm⁻² at an overpotential of 460 mV and fast kinetics (with a Tafel slope of 62.8 mV dec⁻¹) for acidic OER. Meanwhile, the as-prepared heterostructure displays high stability toward acidic OER with maintaining the current density of 10 mA cm⁻² for over 60 h. Detailed characterizations as well as electrochemical in situ spectroscopies reveal that the transfer of electrons across the heterointerfaces enhances the faster lattice-oxygen-mediated mechanism (LOM) pathway, ultimately facilitating the acidic OER process.