Air-mediated phosphoric acid activation strategy for preparation of oxygenated functional groups rich activated carbon for capacitive deionization

Atmosphere during H 3 PO 4 activation is vital to the texture structure and surface-interface properties of activated carbon (AC), but the researches are way out of sufficiency. In this work, it is found that the air in the H 3 PO 4 activation process is not only conducive to the introduction of more-oxidized oxygenated functional groups on ACs, but also beneficial to the formation of micropores rather than mesopores . Besides, as the air content increases in H 3 PO 4 activation, the ACs’ ash, phosphorous content and conductivity reduce, but their wettability , disorder degree and defect number increase. In addition, the potential of zero charge of the as-prepared ACs is positively correlated with the O-C O content, which show a pattern of first increasing and then decreasing with the increase of air content. Benefit from the improved hydrophilicity , electrolyte-affinity, additional adsorption sites for sodium ions , the optimal AC exhibits excellent salt adsorption capacity of 12.08 mg g −1 and good cycling stability at 1.0 V in single-pass capacitive deionization. This work not only establishes a novel and effective method for regulating the texture structure and surface properties of ACs, but also provides promising cathode candidates for capacitive deionization application.