Mn-Based Single Atoms and Nanocrystal Carbon Aerogels for CO ₂ Capture and Energy Storage

The CO2 adsorption and energy storage characteristics of Mn-based single atoms (SAs) and nanocrystals (NCs) (Mn sites stabilized by Mn–O bonds) arrayed in carbon aerogels (CAs), synthesized through a facile/one-pot synthesis route, are evaluated in detail. This involves studying the physiochemical properties of doped CAs with different manganese(II) acetate tetrahydrate ((CH3COO)2Mn·4H2O) loadings and correlating it with CO2 adsorption and energy storage efficiency. Pyrolysis of gel under an inert atmosphere leads to decomposition of (CH3COO)2Mn·4H2O-induced activation of CAs. This dual role of (CH3COO)2Mn·4H2O as a pore-activating agent and catalyst has a significant impact on morphology and porosity. The single ions/nanocrystals of Mn generated thereof act as efficient catalysts, aiding the CO2 adsorption and energy storage. The developed material shows strong potential for direct air capture (DAC), exhibiting remarkable CO2 capture ability (2.54 mmol·g–1 at 15 mbar) along with high specific capacitance (Csp) (136.4 F·g–1 at 0.5 A·g–1 using 1 M KOH solution) and excellent stability of 92% after 3000 cycles at 1 A·g–1.