Morphology, functional groups, and CO2 adsorption performance of Cu2(OH)PO4: Effects of synthesis conditions

Abstract

Global warming, primarily driven by emissions of greenhouse gases, particularly carbon dioxide, has emerged as a widely acknowledged concern. Hence, the development of novel carbon capture materials with high capacity and low cost holds substantial practical significance. This study investigates the influence of aging time, pH, and copper salt on the synthesis of Cu₂(OH)PO₄ and its CO₂ adsorption performance. Cu₂(OH)PO₄ adsorbents were synthesized under various aging time, pH, and copper salt conditions, and their morphology and surface functional groups were characterized. Experimental findings indicate that excessively prolonged or abbreviated aging times adversely affect the formation of distinct, discernible lamellar structures within the material. Different pH levels influence the stacking configuration of the lamellae, impacting both their thickness and size. Under acidic conditions, lamellae exhibit dispersed three-dimensional stacking; under neutral conditions, lamellae notably enlarge and demonstrate two-dimensional stacking; at pH 9, lamellae stack three-dimensionally and aggregate. Additionally, the CO₂ adsorption performance of Cu₂(OH)PO₄ adsorbents synthesized with different copper salts varies. By examining the relationship between surface functional group content and CO₂ adsorption capacity, we deduced the mechanism by which various synthesis conditions affect both surface functional groups and adsorption capacity. Cu₂(OH)PO₄ synthesized with a 24 h aging time, pH 7, and CuSO₄ as the copper salt exhibits the highest CO₂ adsorption capacity, achieving 1.006 mmol/g.