Influence of halide mixing on thermal and photochemical stability of hybrid perovskites: XPS studies

The Stability of Hybrid Perovskites with UiO-66 Metal-Organic Framework Additives with Heat, Light, and Humidity

This study is devoted to investigating the stability of metal-organic framework (MOF)-hybrid perovskites consisting of CH₃NH₃PbI₃ (MAPbI₃) and UiO-66 without a functional group and UiO-66 with different COOH, NH₂,and F functional groups under external influences including heat, light, and humidity. By conducting crystallinity, optical, and X-ray photoelectron spectra (XPS) measurements after long-term aging, all of the prepared MAPbI3@UiO-66 nanocomposites (with pristine UiO-66 or UiO-66 with additional functional groups) were stable to light soaking and a relative humidity (RH) of 50%. Moreover, the UiO-66 and UiO-66-(F)₄ hybrid perovskite films possessed a higher heat tolerance than the other two UiO-66 with the additional functional groups of NH₂ and COOH. Tthe MAPbI3@UiO-66-(F)₄ delivered the highest stability and improved optical properties after aging. This study provides a deeper understanding of the impact of the structure of hybrid MOFs on the stability of the composite films.

Waste-Derived Copper-Lead Electrocatalysts for CO2 Reduction

It remains a real challenge to control the selectivity of the electrocatalytic CO₂ reduction (eCO₂R) reaction to valuable chemicals and fuels. Most of the electrocatalysts are made of non-renewable metal resources, which hampers their large-scale implementation. Here, we report the preparation of bimetallic copper-lead (CuPb) electrocatalysts from industrial metallurgical waste. The metal ions were extracted from the metallurgical waste through simple chemical treatment with ammonium chloride, and Cu_xPb_y electrocatalysts with tunable compositions were fabricated through electrodeposition at varying cathodic potentials. X-ray spectroscopy techniques showed that the pristine electrocatalysts consist of Cu⁰, Cu¹⁺ and Pb²⁺ domains, and no evidence for alloy formation was found. We found a volcano-shape relationship between eCO₂R selectivity toward two electron products, such as CO, and the elemental ratio of Cu and Pb. A maximum Faradaic efficiency towards CO was found for Cu_9.00Pb_1.00, which was four times higher than that of pure Cu, under the same electrocatalytic conditions. In situ Raman spectroscopy revealed that the optimal amount of Pb effectively improved the reducibility of the pristine Cu¹⁺ and Pb²⁺ domains to metallic Cu and Pb, which boosted the selectivity towards CO by synergistic effects. This work provides a framework of thinking to design and tune the selectivity of bimetallic electrocatalysts for CO₂ reduction through valorization of metallurgical waste.