Synthesis of nitrogen-doped mesoporous carbon nanospheres using urea-phenol-formaldehyde resin for efficient CO2 adsorption–desorption studies
Rasmeet Singh, Lizhuo Wang, Junhan Cheng, Haoyue Sun, Chunfei Wu, Jun Huang
Abstract
Global warming led by excessive CO 2 emission is a significant challenge. CO 2 capture is recognised as an efficient way to mitigate this issue. In this study, we successfully synthesized a series of activation-free nitrogen-doped mesoporous carbon nanospheres (M x : where x is ratio of urea/phenol) via an aqueous synthesis route, using urea-phenol-formaldehyde resin as a precursor and triblock copolymer F127 as a soft template. These M x exhibited nitrogen contents ranging from 0.48 % to 1.52 % and with high surface areas within the range of 486.382 to 683.891 m²g⁻¹. Furthermore, they demonstrated a uniform pore channel diameter of around 3.2 nm. The incorporated nitrogen atoms primarily in the forms of pyrrolic, pyridine, and amine groups, offers abundant adsorption sites for CO 2 . The CO 2 adsorption and desorption performance of as-synthesized M x were systematically studied under various CO 2 feed concentrations, including 10 % CO 2 by volume, compressed air (mimicking direct air capture (DAC)), and 10 % CO 2 by volume at 90 % relative humidity, all at 298 K and ∼1 atm. Interestingly, the M 0.1 sample displayed exceptional CO 2 capture performance, achieving a capacity of 2.53 mmol g⁻¹ (or 4.8 mmol m⁻²) at a 10 % CO 2 by volume feed. This outstanding CO 2 adsorption capacity can be attributed to the synergistic effects of ordered mesopore channels, abundant structural micropores, and nitrogen functionalities, facilitating efficient CO 2 adsorption and desorption. Additionally, M 0.1 also displayed high hydrophobicity character, making it ideal for CO 2 adsorption under humid conditions. Moreover, the M x displayed remarkable stability and recyclability, positioning them as promising and environmentally friendly adsorbents for CO 2 capture and separation under practical operating conditions. Additionally, the proposed M x does not need any additional alkali activation before application, thus simplifying the implementation process, reducing costs, and complexity.