Panalytical x pert

The morphologies of different films were characterized by a field emission scanning electron microscope HITACHI SU8010 (Tokyo, Japan). Prior to SEM observation, the films with a dimension of 1 cm width and 1 cm height were precoated with Au for 90 s and then imaged on SU8010 with 5~10 kV acceleration voltage. The element mapping of MPAZ film was characterized by SU8010 equipped with an energy-dispersive X-ray spectroscopy mapping system at 15 kV. XRD spectra were recorded on a PANalytical x’pert (Almelo, The Netherlands) within 10–70° at a speed of 2°/min to identify the special crystalline structure of the composites.

X-ray-diffraction (XRD) analysis with Cu Kα radiation at 40 kV and 50 mA was carried out using a diffractometer (PANalytical X’pert, PANalytical B.V., Almelo, Holland). The samples’ morphology, size, composition, and structure were characterized using field-emission scanning electron microscopy (FE-SEM, TESCAN MARI3, Tescan Ltd., Brno, Czech) and transmission electron microscopy (TEM, FEI TECNAI G2 F20, FEI Co., Hillsboro, OR, USA), combined with energy-dispersive X-ray (EDX) spectroscopy. The samples were measured by XPS using an Al Kα (1486.6 eV) X-ray source on a spectrometer (ESCALAB 250XI, Thermo Fisher Scientific Co., Waltham, MA, USA). The C 1s peak at 284.6 eV was selected for energy calibration to eliminate sample charging during analysis. The adsorption–desorption isotherms of nitrogen were acquired on a surface-area analyzer (JW-BK200A, Beijing JWGB Sci. & Tech. Co., Ltd., Beijing, China) in which all samples were deaerated at 100 °C prior to measurement. Hydrogen adsorption experiment was characterized by adding 30 mg of active materials into 50 mL of 1 M hydrochloric acid solution. After the solution was stirred for 2 h, the centrifugation was carried out and the pH change of the supernatant was measured to determine the amount of hydrochloric acid adsorbed by the active materials.