Escalab 250xi x ray photoelectron spectrometer xps

The surface morphology and crystallinity of the Ti₄O₇ electrode was examined by a field emission scanning electron microscope (FESEM, Model No.: Hitachi S-4800, Japan) and an X-ray diffractometer (XRD, Model No.: Rigaku D/max-2550/PC), respectively. X-ray photoelectron spectroscopy was obtained from a Thermo Fisher Scientific Escalab 250Xi X-ray Photoelectron Spectrometer (XPS) under high vacuum (1 × 10⁻⁹ torr). The total organic carbon of real water samples was measured with a multi N/C 2100 TOC Analyzer (Analytik Jena AG, Germany). An MS5000 spectrometer (Freiberg Instruments Inc., Germany) was employed to obtain the electron paramagnetic resonance (EPR) spectra using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a radical trap. Ammonia concentration was measured by the Nessler reagent method^{15 (link)} using a TU-1810 UV-vis spectrophotometer (Yixin Instruments Equipment Co., Ltd., Shenzhen) at a wavelength of 420 nm. The amount of N₂ produced was calculated from the total nitrogen (30 mg L⁻¹ ammonia) minus the measured concentration of ammonia and nitrate. NO₃⁻ and NO₂⁻ concentrations were determined with a DionexTM ICS-5000 ion chromatography system (IC, Thermo Fisher, USA). NB concentration was quantified by a waters 3000 high performance liquid chromatography system (UHPLC, USA) coupled with a C18 column at 262 nm.