Asap 2420

BET specific surface area, micro, meso and macroporosity of the shale samples were analysed using a Micrometrics ASAP 2420 instrument. Using N₂ as the adsorbate at −196 °C, isotherms were acquired from 0.001 to 0.998 relative pressure. About 3 g of shale samples (2–5 mm) were placed into a glass tube with filler rod. Dry samples were vacuumed dried at 80 °C for 15 h prior to analysis. Wet samples (50% RH equilibrated) were frozen at −196 °C in liquid N₂ for 30 min in the glass tube with filler rod prior to analysis, with the instrument and sample taken to vacuum manually with frozen water held in the pores and surface of the samples. This method eliminates the free space procedure as the isotherm is started immediately as the vacuum set-point is reached (0.013 mbar), therefore a separate free space analysis was carried out on blank tubes similar to the method above for methane adsorption. Surface areas of the shale were calculated using BET surface area equation from 0.05 to 0.25 relative pressure giving positive BET C values^{41 (link)}. Micro and mesopore volumes were determined using Horvath-Kawazoe model, assuming slit pore geometry on a carbon/graphite surface.

The relationship between
adsorbed gas molecules and the partial pressure at constant temperature
was registered in adsorption isotherms. The mathematical adjustment
of these isotherms to different theoretical models was used to provide
information on the volume adsorbed at a given pressure, enabling the
calculation of values, such as the surface area of the solid and the
pore volume.
High-resolution CO₂ adsorption isotherms
up to 1 bar were measured in a Micromeritics ASAP 2010 for PdIn-MOF. Approximately 150 mg of solid was immersed into a liquid circulation
thermostatic bath within a glass sample holder. The adsorption was
studied after an overnight activation step at 80 °C under vacuum.
Then, the CO₂ adsorption isotherm at 0 °C was measured.
The Dubinin–Astakhov plot for CO₂ adsorption at
0 °C was used.
On the other hand, nitrogen adsorption isotherms
(for BET area)
for the MOF-derived composites were recorded in an ASAP 2420 apparatus
from Micrometrics at −196 °C from 0 to 1 of relative pressure
(P/P₀). First, 150 mg
of pelletized sample (0.2–0.4 mm) was degassed at 400 °C
at ≈5×10^–6 bar overnight. The BET surface
area was calculated by using the Brunauer–Emmet–Teller
equation fulfilling the criterion established by Rouquerol et al.,^{49 (link)} and micropore volume was calculated by the t-plot
method.

To estimate the specific surface area of the synthesized nanoparticles, the samples were weighed and degassed. The degassing was carried out at 300 °C and about 200 mTorr for 24 h. After that, the samples were cooled to room temperature and inserted into sample ports of the ASAP 2420 MICROMETRICS instrument (Norcross, GA, USA). Nitrogen adsorption isotherms were measured at 77 K. The BET equation was used to calculate the specific surface areas [40 (link)].

Textural properties of the used biochars were determined using low-temperature nitrogen adsorption-desorption isotherms method (sorptometer ASAP 2420, Micrometrics, Norcross, GA, USA). Before the measurement, the solids were degassed at 200 °C under vacuum. Specific surface area (S_BET) and pore size distribution (PSD) of the samples were calculated using BET and BJH methods. The total pore volume (V_t) was established at a relative pressure p/p₀ = 0.99.

The morphologies of synthesized particles were characterized by using a scanning electron microscope (SEM; Hitachi S-4300) and a transmission electron microscope (TEM; Hitachi-7400). Cross-sectional SEM images were obatined by Carl Zeiss AURIGA after FIB milling, and more detailed TEM images and elemental analyses were performed by using an analytical TEM (FEI Tecnai F20) equipped with an energy dispersive spectroscopy (EDS) system. UV-Vis absorbance spectra were obtained with Beckman DU 650 spectrophotometer, and diffuse reflectances were measured by using Jasco V-670 spectrophotometer with an integrating sphere. X-ray diffraction (XRD) patterns were obtained by using Rigaku D/MAX 2500 V with Cu Kα radiation source, and Brunauer-Emmett-Teller (BET) analyses were performed with Micrometrics ASAP 2420. Photoelectrochemical evaluations of DSCs were performed by obtaining photocurrent density-voltage curve under incident AM 1.5G light (intensity: 100 mW/cm²) by using a solar simulator (XIL model 05A50KS source measure units equipped with an AM 1.5G filter) and a potentiostat (Solartron 1480). Incident photon-to-current efficiency (IPCE) spectra were obtained by McScience K3100, and electrochemical impedance spectra were measured by using Zahner Zennium with the sinusodial perturbation of 10 mV.