Sol-Gel Synthesis of NiO nanoparticle using Excess CO2 Acidification(ECA)

A novel sol–gel-based Excess CO₂ Acidification (ECA) method was proposed to synthesize uniform metal oxide nanoparticles with consistent size, morphology, and mesoporosity. In this method, CO₂ was over-sparged into a buffered KOH solution to generate an acidic bicarbonate buffer, followed by addition of metal precursor solutions and controlled reduction of CO₂ concentration established a proton concentration gradient. This approach ensures homogeneous sol–gel reactions, prevents localized pH spikes, and minimizes thermal-induced structural changes. The synthesized nanoparticles exhibited consistent particle size distribution and enhanced mesoporosity. Compared to conventional pouring or titration sol-gel methods, ECA reduces reaction time, reactor volume, water footprint, and energy consumption, while improving particle harvest efficiency. The method is versatile and can be applied to the synthesis of various metal oxide nanoparticles, optimization of magnetic and catalytic properties, Sequential solvent exchange, and potential reuse of residual KOH solutions for microbial or colloidal applications. In summary, the ECA technique provides a scalable, efficient, and sustainable strategy for producing high-quality mesoporous metal oxides suitable for industrial applications.