Inductively Coupled Plasma Optical Emission spectroscopy (ICP-OES)
The method allows determining the content of selected elements in synthesized materials. It can detect the elements with concentration as low as low as …
It is particularly important for our work in i.e.:
- Verifying the efficiency of washing steps after molten salt synthesis of carbons and to estimate the amount of metallic species remaining in the material [ref]
- Determining the amount of metallic species in single atom or single sites catalysts [ref]
- Checking the amount of metallic species in “metal-free electrocatalysts”
Gas sorption measurements
Large surface area is important for applications as catalysis or energy storage. The adsorption and desorption of gases is used to characterize the porous structure and chemical nature of the materials. In our group, we use regularly 3 different sorption gases: N2, CO2 and water vapors. Sorption of N2 allows calculating pore size distribution, surface area, pore volume and many more. It is the standard method for detection of pores between 0.5 and 50 nm. For detection of smaller pores, we use CO2, which has lower kinetic diameter compared to N2. Sorption of water vapors helps to determine the chemical state of the pore walls (hydrophilic / hydrophobic character).
Temperature programmed desorption (TPD)
Using temperature programmed desorption of CO2 and NH3 we are able to understand the strength of acid, and basic sites on the surface of our heteroatom doped carbonaceous materials. The method consist on loading at room temperature the different gases by injecting pulses through the sample until the material is not adsorbing the gas any more. Then the sample is submitted to a heat treatment and the gases being realized are analyzed. Depending of the strength of the sites, the adsorbed molecules will be released a different temperatures (i.e. larger temperatures for stronger sites).
It gives us information about morphology, structure and composition of materials. In the case of carbon materials, it is very useful to see if a material is homogenous or not. It is prerequisite for determination of single atom / single sites catalysts.
In our institute, we have a dedicated and highly qualified research group able to perform all sorts of electron microscopy including SEM, TEM, HR TEM, HAADF-STEM, EELS and many more. To learn more visit their webpage (Dr. Hab. Tarakina webpage).
Powder X-ray diffraction (XRD)
It is a basic technique to determine whether our materials are crystalline or amorphous. Most of carbonaceous materials are amorphous; however, high enough temperature during carbonization can enhance graphitization process increasing atom ordering.
One powerful strategy in the synthesis of carbon materials with controlled structure and heteroatom content is to use supramolecular precursors, which show specific pre-organization for carbonization. In that case, XRD helps to detect and characterize such precursors.
Thermogravimetry coupled with mass spectrometer (TG-MS)
This technique enables investigation of sample behavior during its thermal treatment through the detection of mass loss and the analysis of gaseous products evolved during the process. Thanks to that, we can determine:
- The carbonization temperature of carbon precursors
- The nobility of carbon materials (their resistance to oxidation while calcining in air).
- The thermal stability of the material
- Mechanism of the synthesis of carbon materials
Raman and infrared spectroscopy
Those two techniques allow detecting types of chemical bonds in the material. Therefore, they help to determine the chemical composition of the samples.
- Evaluating the conjugation of the carbon structure
- Calculating the level of graphitization
- Detection of heteroatoms and potentially adsorbed water
It is used to evaluate the amount of basic elements of carbon materials: C, N, S, H and O. This gives us information on:
- Chemical composition of carbons
- The level of carbonization
- The content of heteroatoms