Kinetic interface design in carbon-doped Mg(OH)2 enables concurrent CO2 blocking and capture

Abstract

In this study, we report a kinetically engineered Mg(OH)₂-based nanostructure that simultaneously blocks carbonate passivation and contributes to CO₂ capture. The material was synthesized via a non-equilibrium spray drying process followed by calcination at 350 °C and facile steam treatment producing carbon-doped MgO–Mg(OH)₂ nanoparticles with a dual-function interfacial architecture. While conventional Mg(OH)₂ regions can mitigate MgCO₃ formation by acting as CO₂ diffusion barriers, they consume active MgO, thereby lowering overall sorbent capacity. Here, carbon doping transforms the role of Mg(OH)₂: it not only limits carbonate growth but also introduces oxygen vacancies and defect sites that actively adsorb CO₂. The non-equilibrium kinetically driven conditions of spray drying kinetically trap carbon species near the surface, forming self-limiting, carbon-rich Mg(OH)₂ regions around reactive MgO domains. This architecture achieves a CO₂ uptake of 5.45 wt% at room temperature with a low regeneration temperature of 150 °C, despite having a lower surface area than its undoped counterpart. Cyclic tests revealed 62% capacity retention after five regeneration cycles at 150 °C, owing to gradual active site saturation. These findings demonstrate that controlled carbon enrichment and defect engineering in Mg(OH)₂ unlock its dual role, acting both as a protective interface and as a reactive sorbent, enabling efficient and regenerable CO₂ capture.