Synergistic Atomic-level Anchoring and Pore Engineering of Cobalt-Nitrogen-Carbon for Anti-fouling and Robust Capacitive Deionization

Huakun Pan ^a, Haodong Zhang ^a, Xinxi Teng ^a, Yang Fan ^a,*, Yaming Wang ^a, Lin Li ^a, Guisong Zhang ^a, Meiling Liu ^a, Haiou Song ^b,*, Aimin Li ^c, Shupeng Zhang ^a,*

^a School of Chemistry and Chemical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, PR China

^b School of the Environment, Nanjing Normal University, Nanjing 210023, PR China

^c School of the Environment, Nanjing University, Nanjing 210023, PR China

ABSTRACT

Capacitive deionization (CDI) represents a promising energy-saving technology for addressing freshwater scarcity, but suffers from electrode fouling and pore blockage in real-world organically contaminated water. This work introduces a cobalt-nitrogen co-doped biomass-derived electrode (Co-NLE) designed to mitigate structural collapse and fouling in conventional electrodes through atomic-level Co-N_x coordination anchoring and hierarchical pore architecture. Characterization confirms that Co-N_x centers enhance carbon layer crosslinking, preventing framework collapse during high-temperature nitrogen doping. Consequently, Co-NLE exhibits over ten-fold higher specific surface area and superior hydrophilicity compared to solely nitrogen-doped carbon. The pore-optimized Co-NLEAC electrode achieves a salt adsorption capacity (SAC) of 22.33 mg g^-1 in 50 mg L^-1 NaCl and maintains 21.22 mg g^-1 SAC with 10 μg L^-1 humic acid. It retains 80% of maximum SAC in multi-organic systems and demonstrates effective adsorption for various cations, indicating its potential for industrial applications such as hard water softening and lithium-ion battery recycling. This study establishes an advanced material paradigm for the application of CDI technology in wastewater treatment under complex systems.

This work converts agricultural and forestry waste into high-performance CDI electrodes through a cobalt-nitrogen synergistic doping strategy. Due to the synergistic effect of Co-Nₓ coordination anchoring and hierarchical pore engineering, Co nanoparticles were generated to suppress the collapse of carbonized structures at high temperatures while catalytically inducing the formation of a hierarchical micro-mesoporous architecture within the carbon matrix. Concurrently, Co-N bonds polarize the electron cloud distribution of the carbon substrate, enhancing surface hydrophilicity. The resulting Co-NLEAC electrode material achieved a salt adsorption capacity of 22.33 mg g^-1 in 50 mg L^-1 NaCl solution, showing a significant improvement compared to single nitrogen-doped materials; under the coexistence of 1 mg L^-1 complex organic pollutants, it still maintained over 80% performance, and the capacity retention rate exceeded 90% after 20 cycles in complex systems. This work demonstrates the feasibility of converting agricultural and forestry waste into high-performance CDI electrodes and provides an effective strategy for developing anti-pollution CDI electrodes, offering a sustainable material solution for distributed water treatment.

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