Tga 55 instrument

A TGA 55 instrument (TA Instruments, New Castle, DE, USA) was utilized to obtain the TGA data. A 3–5 mg powder sample was put in an alumina oxide pan without cover; then, the pan was heated from 25 °C to 410 °C at a heating rate of 10 °C/min. Nitrogen gas was applied as purge gas, and its flow rate was set as 20 mL/min. TA TRIOS 5.1 software was applied to process and analyze the collected TGA data.

Morphology and composition of the samples were characterized using SEM (EM S-4800, Tokyo, Japan) coupled with energy dispersive spectroscopy (EDS). All the specimens were gold-sputtered and tested at an accelerating voltage of 15 kV.
Microstructure of the LRF carbon cryogel was characterized using TEM (Tecnai G2 F20 S-TWIN, FEI, USA).
FTIR tests were performed on a Vertex 70 spectrophotometer (Bruker, Germany) equipped with an attenuated total reflectance (ATR) cell. The wavenumber region ranged from 4000 to 400 cm⁻¹ with a resolution of 4 cm⁻¹. Each specimen was tested twice.
XRD patterns were recorded on a D8 Advance diffractometer (Bruker, Germany) using Cu Kα radiation at a 2θ angle range of 2–40°, with a scanning step of 0.01° and a scanning rate of 2° min⁻¹.
TGA was tested on a TGA–55 instrument (TA, New Castle, DE, USA). Each sample ran from 30 to 800 °C at a heating rate of 10 °C min⁻¹ under N₂ atmosphere.
N₂ adsorption–desorption isotherms were determined using an ASAP 2460 automated gas sorption analyzer (sn:506, Atlanta, GA, USA). The specific surface area (SSA) was calculated by the Brunauer–Emmett–Teller (BET) method, the pore size distribution (PSD) by the Barret–Joyner–Halenda (BJH) model, and the micropore distribution by the t-plot method.