Potassium and chlorine co-tuned graphitic carbon nitride for organic pollutants photodegradation: Revealing the effects of cyano groups on O2 evolution

[Display omitted] •Cyano groups acting as the most stable adsorption site promoted O2 adsorption.•Cyano groups served as charge transfer bridge between CN-KCl catalyst and O2.•K/Cl co-doping enhanced the migration of electrons across layers and lamellae.•Cl replaced sp2-hybridized nitrogen atom, and K doped at the interstitial site. The insufficient active sites and sluggish photogenerated electron migration are hindered the photocatalytic activity of g-C3N4. Herein, we successfully synthesized a K and Cl co-tuned g-C3N4, with cyano groups incorporating (expressed as CN-KCl). The optoelectronic and physicochemical properties of the samples were comprehensively investigated using a combination of characterization techniques and DFT calculations. The results demonstrated that Cl atom replaced sp2-hybridized nitrogen atom, while K atom was doped at the interstitial site. With the synergistic effect of K/Cl atoms, the transfer of photogenerated electrons across layers and lamellae was enhanced. Additionally, the cyano groups not only acted as the most stable adsorption sites for O2, but also served as charge transfer bridge between catalysts and O2, enhancing the activation of O2. This ultimately led to an improvement in the generation of superoxide radicals and contributed to the enhanced photocatalytic activity of CN-KCl.