NaNO₂-loaded mesoporous MgO for high-efficiency CO₂ capture: Synthesis, characterization and novel mechanistic insights

Abstract

The development of efficient CO₂ adsorbents is critical for achieving net-zero targets. MgO represents a promising solid adsorbent for CO₂ capture, yet its limited specific surface area and insufficient active sites restrict its adsorption capacity under moderate temperature conditions. A rod-like anhydrous MgCO₃ precursor was hydrothermally synthesized and calcined at 500 °C for 3 h to obtain porous MgO (184.9 m² g⁻¹, 0.38 cm³/g), which was then modified with 20% NaNO₂ (by mole) via impregnation. This adsorbent achieved an adsorption capacity of 12.6 mmol g⁻¹ after 120 min under a pure CO₂ atmosphere at 325 °C. Comprehensive characterization reveals that NaNO₂ modification leads to the NaNO₃ and Na₂CO₃ formation on the MgO surface during calcination. The introduced NaNO₃ effectively promotes oxygen vacancy formation, while the generated Na₂CO₃ serves as heterogeneous nucleation sites, collectively reducing the reaction energy barrier and enhancing interfacial mass transfer. This synergistic effect facilitates the MgCO₃ formation followed by its conversion to the thermodynamically more stable Na₂Mg(CO₃)₂. Kinetic studies elucidate that adsorption is dominated by surface chemical reactions and diffusion mechanisms at different stages. These fundamental insights into the adsorption mechanisms of nitrite-modified MgO provide valuable guidance for the rational design of advanced MgO-based CO₂ adsorbents with enhanced performance.

Keywords

CO₂ capture / MgO-based adsorbents / NaNO₂ loading / NaNO₃ and Na₂CO₃ / Synergistic effect

CRediT authorship contribution statement

Yulian Wang: Writing – review & editing, Writing – original draft, Validation, Supervision, Resources, Funding acquisition, Conceptualization. Jiayi Liu: Writing – review & editing, Writing – original draft, Resources, Project administration, Methodology, Formal analysis, Data curation. Jinze Song: Software, Data curation. Junze Gu: Methodology, Investigation. Binyan Wang: Methodology. Rui Guan: Writing – original draft, Data curation, Conceptualization. Keqing Li: Software. Wanzhong Yin: Supervision, Investigation. Haoran Sun: Investigation. Huili Han: Visualization.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work was financially supported by National Natural Science Foundation of China (Nos. 52374271 and 52404290), Liaoning Province’ Xing Liao Ying Cai Program’ Outstanding Young Talents Project (No. XLYC2403010), Applied Basic Research Programs of Key Research and Development Program of Liaoning Province of China (No. 2025JH2/101300041), Liaoning Provincial Engineering Research Center for High-Value Utilization of Magnesite (No. LMKK20240101), and Research Fund Project of Liaoning Provincial Education Department (Nos. SYLUGXRC+12 and LJMKZ20220585), and Program of China Scholarship Council (No. 202506080127). The authors would like to thank Scientific Compass (www.shiyanjia.com) for providing EPR testing.

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