Thermoporometry of porous carbon: The effect of the carbon surface chemistry on the thickness of non-freezable pore water layer (delta layer)

The effect of the amount of oxygen in carbons on the quantity of non-freezable pore water was studied to evaluate and to develop a simple methodology for the determination of the delta layer (delta). Porous carbon was oxidized by different ways to obtain samples with different surface oxidation degrees. It was found out that with the increasing oxygen content in carbonaceous samples, the amount of non-freezable water increases. Based on the quantity of unfrozen pore water and texture properties (from gas physisorption experiments), several approaches (4 in total) for the determination of the delta were tested. Regardless of the concrete approach, it was proved that the delta layer is not constant, but it strongly depends on the carbon chemistry in the way that its thickness significantly increases with increasing amount of oxygen (in the range of 0.46-2.72 nm in our case). To obtain reliable results (porosity information) from thermopommetry experiments it is necessary to take into account the surface chemistry and (in ideal case) to estimate the width of delta layer for specific class of materials by preliminary experiments. The suggested approaches for the evaluation of the delta layer value aim to making the thermoporometry a wide-spread method.

Automated summary

The study focuses on the effect of oxygen content in carbons on the amount of non-freezable pore water, showing that the quantity of non-freezable water increases with increasing oxygen content. By taking into account the surface chemistry of carbon materials, it was found that the thickness of the delta layer significantly increases with increasing amount of oxygen. The proposed approaches aim to make thermoporometry a widely-used method by estimating the width of the delta layer for specific materials.