Sol-gel synthesis, characterization and catalytic activity of manganese-doped calcium cobalt oxide

Abstract

This study investigates manganese-doped calcium cobalt oxide (MCCO - Ca₃Co2-xMnₓO₆, x = 0–0.3) as a catalyst for the environmentally significant reduction of 4-nitrophenol (4-NP). While cobalt oxides are known catalysts, this work provides the first systematic evaluation of Mn-doping effects in Ca₃Co₂O₆ for this application. MCCO materials were synthesized via sol-gel, with FTIR confirming phase formation after 10 h of calcination 1000◦C and XRD revealing lattice parameter shifts consistent with Mn incorporation. SEM and BET analyses showed that Mn doping significantly altered particle morphology and textural properties, including non-monotonic changes in specific surface area. Catalytic evaluation using NaBH4 showed optimal performance for the MCCO sample with x = 0.1, achieving the highest apparent rate constant (kₐₚₚ = 0.412 min⁻¹) and 98.77 % 4-NP reduction efficiency within 10 min at pH 8. This composition also demonstrated good reusability, retaining 94.76 % efficiency after eight cycles. These findings highlight the critical role of Mn doping level in tuning the structural properties and catalytic performance of Ca₃Co₂O₆, identifying MCCO-0.1 as a highly efficient and reusable catalyst for 4-NP reduction.