Electrochemical CO₂ reduction (CO₂R) to chemicals and fuels has made tremendous progress since the introduction of gas diffusion electrodes (GDEs) to overcome mass-transfer limitations and enable industrial-scale current densities. The advancement in the field, however, has come with new challenges that are related to the stability and degradation of the GDE due to flooding issues, which currently hinder the scale-up. Here, we investigated the effect of six different binding materials (Nafion, polytetrafluoroethylene, Fumion, Pention, poly(vinyl alcohol), and polypyrrole) on the stability and performance of Ag-based GDEs for CO₂R to CO in alkaline media. All binders show a decrease in the Faraday efficiency (FE) of CO and increase in hydrogen evolution reaction over time. The most hydrophilic GDE based on polypyrrole can uphold a higher FE of CO for longer times, which is contrary to a common belief that low wettability is required for long-term stability. By using a range of tools (SEM-EDX, SEM-FIB, X-ray diffraction, and contact angle measurements) for the postelectrolysis characterization of the GDEs, we show that the performance loss is related to flooding, bi(carbonate) precipitation, and catalyst agglomeration. These results contribute to a better understanding of the stability issues in GDE-based CO₂ electrolyzers.

The development of an effective and reliable sensor with the capability to detect ammonia (NH₃) gas at room temperature exerts a significant influence on the sensor industry. The gas sensing performance is notably improved by the formation of a heterostructure between metal oxide with metal sulfides. In this study, pure ZnIn₂S₄ (ZIS), Cu₂O and heterostructures of ZIS with 5, 10 and 20 wt% of Cu₂O were successfully prepared using hydrothermal, co-precipitation and heat treatment methods, respectively. A thorough investigation has been carried out to examine the sensing capabilities of all the materials upon exposure to NH₃ with different concentrations (1, 5, 10, 15, 20, 25 and 50 ppm) at room temperature (RT). Impressively, the composite material 0.9ZnIn₂S₄/0.1Cu₂O (ZIS-10) has exhibited remarkable gas sensitivity compared to pristine ZIS and Cu₂O towards 25 ppm NH₃, low limit of detection (1 ppm) with fast response/recovery times (37/25 sec). The improved performance of the ZIS-10 composite sensor may be ascribed to the synergistic effect between ZIS and Cu₂O, which facilitates the electron transfer from ZIS to the Cu₂O at the interface. The plausible gas-sensing mechanism and the pathways responsible for enhanced sensing are also discussed in detail.

The influence of ageing under ambient conditions on the corrosion protective behaviour of a lithium-based conversion layer on AA2024-T3 is studied in this work. Conversion layers aged at ambient conditions for relatively short times (0 h and 4 h), show an initial high degree of corrosion inhibition but a much lower protectiveness after the inhibition stage terminates. Conversion layers with relatively long ageing times (24 h and 72 h) show a rather stable corrosion resistance which is higher than that of short-time aged samples. It is hypothesized that the freshly-formed conversion layer has trapped a certain amount of lithium ions and water molecules, leading to ongoing and heterogeneous growth of the conversion layer with time under ambient indoor conditions. Moreover, conversion layers with short ageing times show early-stage active corrosion protection by lithium-ion release.