Effects of carbonyl group formation on ammonia adsorption of porous carbon surfaces

In this work, the effects of different surface functional groups on the ammonia adsorption of porous carbons modified by electrochemical treatment in acidic solution (HNO3) under different current densities were investigated. The surface properties of the treated carbons were observed by Boehm's titration and X-ray photoelectron spectroscopy (XPS). It was found that the oxygen content of the carbons increased with increasing current density from the XPS results. However, the pH and acid values of the treated carbons slightly decreased in a sample prepared in 0.8 A/m2 of current density (ACs-0.8). This result indicated that the surface acidity could be reduced according to the characteristics of surface functional groups introduced. From the XPS results, it was found that the growth of CO groups was predominant at ACs-0.8. This result was also supported by an ammonia gas removal test. The adsorption capacity increased to ACs-0.4, but then began to decrease at AC-0.8.

Graphical abstractAll of the oxidized samples showed a higher adsorption capacity than that of the as-received sample, and the adsorption capacity increased with increasing current density up to ACs-0.4, and then decreased due to the decrease of acidity at ACs-0.8 (we considered that the change of pore structures was negligible between ACs-0.4 and ACs-0.8, compared with that of adsorption capacity).Figure optionsDownload full-size imageDownload as PowerPoint slide