Advances in Manganese Oxide Research: Environmental Geochemistry to Biogeochemical Cycling and Sustainable Catalysis

Manganese oxides have emerged as a focal point of extensive research due to their multifaceted roles in various scientific domains. This comprehensive review article delves into the diverse facets of manganese oxides, spanning from their crucial involvement in environmental geochemistry to their pivotal role in biogeochemical cycling. These minerals exhibit a broad spectrum of redox chemistry, from Mn(II) to Mn(IV) and Mn(VII), allowing them to partake in a variety of catalytic processes. The article explores the impact of pH on the stability and reactivity of different manganese species, illustrating the relevance of these compounds across the acidic to alkaline pH spectrum. Furthermore, it delves into their significance in advanced oxidation processes for water treatment, particularly the potent MnO4–/HSO3–  system. The article also unveils the pivotal role of manganese oxides in anion-exchange membrane fuel cells and electrolyzers as alternatives to noble metal catalysts for oxygen reduction and evolution reactions. Lastly, this review underscores the importance of understanding the thermodynamic stability of various manganese species under different conditions. It serves as a valuable resource for researchers and scientists exploring the multifaceted world of manganese oxides and their diverse applications across various scientific disciplines.