This study investigates the degradation mechanism of silk fibroin through Fourier-transformed infrared spectroscopy (FTIR) analysis. The secondary structure of silk fibroin-based materials is monitored using FTIR, and various estimators are calculated to assess the impact of degradation conditions and aging time. The oxidation estimator shows consistent growth, indicating peptide bond oxidation from the early stages of artificial aging, regardless of the conditions. The environment influences the hydrolysis estimator, with water introduction leading to significant changes. The crystallinity estimator reflects the overall degradation level, affected by oxidation and hydrolysis. XRD and FTIR analysis of historical silk banners up to 500 years old demonstrate a decrease in crystallinity and an increase in hydrolysis and oxidation. The presence of water accelerates the oxidation process, while crystallinity changes are primarily driven by oxidation. Fibroin degradation affects both antiparallel and parallel regions, with water playing a crucial role in accelerating hydrolysis and causing structural shifts. This study enhances our understanding of silk fibroin degradation and provides valuable insights for preserving historical silk artifacts.

Methane combustion over palladium-based catalysts is a critical process for reducing greenhouse gas emissions from lean-burn engines and natural gas installations, yet the role of oxide support in controlling both the population and the intrinsic reactivity of Pd active centres remains incompletely understood. In this work, Pd catalysts at two series of higher and lower loading were prepared on five oxide supports—Al₂O₃, CeO₂, SiO₂, TiO₂, and ZrO₂—and characterised by a complementary suite of techniques including SEM-EDX, XRD, BET, AAS, in situ CO-FTIR, DRIFTS with methanol as a probe molecule, and Raman spectroscopy. Catalytic activity testing revealed the order Pd/CeO₂ > Pd/ZrO₂ > Pd/Al₂O₃ > Pd/TiO₂ > Pd/SiO₂. In situ CO-FTIR site quantification showed that active site density spans nearly an order of magnitude across the series, with Pd/CeO₂ reaching 105.44 µmol g⁻¹ and Pd/Al₂O₃ only 11.63 µmol g⁻¹. Turnover frequency analysis revealed a striking inversion: Pd/Al₂O₃ exhibited the highest TOF (0.1327 s⁻¹), approximately six times greater than Pd/CeO₂ (0.0226 s⁻¹). DRIFTS/methanol profiling demonstrated that CeO₂ and ZrO₂ expose cooperative redox and basic centres that promote methane activation, while SiO₂ supports only weakly bound methoxy species, consistent with its lowest activity. These results establish that the oxide support simultaneously governs Pd dispersion—and hence site density—and the electronic environment of each Pd centre, thereby modulating intrinsic reactivity. High specific surface area alone does not guarantee catalytic performance, and rational support selection is therefore the decisive lever for optimising methane combustion catalysts at ultra-low Pd loadings. In all, our findings provide a quantitative, molecular-level framework that disentangles support-controlled site density from intrinsic site reactivity under identical reaction conditions. By combining in situ CO-FTIR, DRIFTS, and Raman spectroscopy with kinetic analysis on well-defined, high-purity oxide supports, this work transforms previously qualitative “support effects” in Pd-catalysed methane combustion into predictive structure–activity relationships.

Palladium supported on oxide carriers is among the most active catalyst systems for methane combustion, yet the role of the support in governing Pd speciation and reaction pathways remains incompletely resolved. Here, ultra-low-loading Pd/Al₂O₃, Pd/SiO₂, Pd/TiO₂, Pd/ZrO₂ and Pd/CeO₂ catalysts were investigated by quantitative CO-FTIR site counting, in situ DRIFTS using CH₄, CO and HCOOH probe molecules, and fixed-bed kinetic testing. CO-FTIR revealed support-dependent populations of CO-accessible Pd centres, with experimentally determined CO absorption coefficients providing the basis for their quantification. The low apparent activation energies and convergence of the high-temperature rates indicate a substantial contribution from mass transport, limiting the kinetic comparison to apparent catalytic performance. Across CH₄, HCOOH and CO sorption experiments, methane oxidation is consistent with a proposed methoxy → formate → carbonate sequence whose extent and thermal stability are support-dependent. CeO₂ and ZrO₂ enable carbonate formation and removal, Al₂O₃ favours carbonate retention, and SiO₂ shows no reliably detectable chemisorbed intermediates. These findings link quantitative Pd site counting with a support-resolved mechanistic hierarchy, suggesting that efficient methane combustion benefits from both dispersed PdO/Pd⁺ centres and a redox-active support that promotes oxygenate turnover rather than surface trapping.