Low-temperature molten salt synthesis of Na, K-codoped g-C3N4 Fenton-like catalyst with remarkable TCH degradation performance in a wide pH range

•Na, K-codoped g-C3N4 Fenton-like catalyst were synthesized by a molten salt method.•The density of single electrons of NKCN is obviously improved.•It exhbits remarkable TCH degradation performance in a wide pH range in dark.•The O2− radicals are the main active species during TCH degradation in dark. A Na, K-codpoed g-C3N4 Fenton-like catalyst (NKCN) was prepared by a low-temperature molten salt method at 300 °C in KNO3-NaNO2 system for the first time. The density of single electrons of NKCN is obviously improved by doping Na+ and K+ as well as the formation of more N vacancies. This NKCN material can efficiently activate H2O2 to generate O2− radicals, which can efficiently degrade tetracycline hydrochloride (TCH, a typical emerging aqueous pollutant) in a wide pH value range (4.04–9.22) in dark. Its rate constant (k) is 52 and 8.7 times those of g-C3N4 and Fe2O3, respectively.