Low-temperature hydrogenation of nanodiamond as a strategy to fabricate sp³-hybridized nanocarbon as a high-performance persulfate activator

This study presents the first instance of the application of hydrogenated nanodiamonds (H-NDs) for persulfate activation and the associated organic degradation. Surface hydrogenation at 600 ℃, confirmed by the increased surface density of the C-H moiety in XPS and FT-IR spectra, produced H-NDs that outperformed graphitized NDs (prepared via annealing at 1000 ℃) in terms of organic degradation and persulfate utilization efficiency. Hydrogenation improved the electrical conductivity of NDs; however, it was not accompanied by an increase in the sp² carbon content − in contrast to energy-intensive ND graphitization − resulting from sp³-to-sp² carbon transformation. In addition to the enhanced electron-transfer mediating activity, evidenced by the negative shift of the open circuit potential and current generation, isothermal titration calorimetry measurements indicated a significantly higher binding affinity of H-ND toward persulfate compared with that of graphitized ND. Multiple empirical results confirmed the progress of electron-transfer mediation as a major activation pathway.