Mn-based noble metal-free electrocatalysts: advancing the OER and the ORR through innovation and future insights

Manganese-based electrocatalysts are attracting significant attention as sustainable, earth-abundant candidates for oxygen evolution and reduction reactions in advanced electrochemical energy systems, owing to their low toxicity and versatile redox chemistry. This article provides a comprehensive review of the structural diversity and catalytic potential of Mn-based materials including oxides, chalcogenides, phosphides, nitrides, borides, metal-organic frameworks, and single-atom catalysts while highlighting their environmental compatibility. Key challenges such as low conductivity, limited active site density, structural instability, and suboptimal electronic structure are critically examined. The review places a special emphasis on strategies like defect engineering, heteroatom doping, and electronic modulation particularly tuning the d-band center and e_g orbital occupancy to enhance catalytic performance, achieve balanced adsorption energies, and accelerate reaction kinetics. Notably, several effective solutions, including the integration of conductive supports and hybridization with robust substrates or secondary metals, are demonstrated to improve both efficiency and durability, underscoring the growing promise of Mn-based electrocatalysts for next-generation energy technologies.