Mesoporosity assessment by thermoporometry: comparison of calibration method and delta layer width determination approach

Thermoporometry (TPM) based on differential scanning calorimetry is a useful technique for mesopore characterization, particularly for wet, fragile, or drying-sensitive materials. However, TPM data evaluation is strongly affected by the applied calculation approach, especially by the treatment of the non-freezable liquid layer, so called delta layer ( δ ). In this study, two TPM evaluation methods, the calibration-based method and the δ layer estimation method, were investigated for three silica samples and two porous carbon materials differing in pore sizes. The results were compared to nitrogen physisorption as a complementary technique. Both TPM approaches provided reasonable pore size distributions and followed similar trends across the studied samples. Good correspondence with nitrogen physisorption was observed mainly for materials with narrow and well-defined small mesopores. The calibration method generally produced sharper pore size distribution (PSD) peaks and maxima closer to those obtained from nitrogen physisorption, while the δ layer method shifted PSDs slightly toward larger pore diameters due to the influence of the δ size. For broader PSD containing large mesopores and small macropores, TPM analysis became more challenging because of overlap between pore and bulk ice melting signals, although useful porosity information was still obtained. Mesopore volumes determined by TPM were generally lower than those obtained from nitrogen physisorption, which may result from differences in pore accessibility, wetting, experimental conditions, theoretical assumptions and data evaluation procedures of the two techniques. Overall, the empirical calibration method is suitable for rapid routine TPM evaluation, whereas the δ layer method provides a more physically based description of systems in which interfacial effects are expected to be significant.