A microcalorimetric study of the adsorption of propane on MoVTeNb oxide

Polycrystalline, mixed MoVTeNb oxides have been reported to show high selectivity and activity in the oxidation of propane to acrylic acid. The most relevant crystal structure in C-H activation of propane is the orthorhombic, bronze-like M1 phase. In the present work, the adsorption of propane on the surface of M1 has been studied by microcalorimetry. The investigation is aimed at a deeper understanding of the mechanism of propane activation. A series of highly crystalline, phase-pure M1 catalysts was prepared. The M1 catalysts were tested in propane oxidation to acrylic acid. At propane conversion of approximately 50%, the selectivity to acrylic acid differs by an order of magnitude. Highly selective M1 is characterized by comparatively strong adsorption of propane (∆Hads~60 kJ/mol). The heat of adsorption is independent of the coverage suggesting homogeneous distribution and uniformity of adsorption sites. Nano-structuring of M1 results in weaker adsorption (∆Hads~45 kJ/mol) and inhomogeneity, which may be connected with low the selectivity

GO-TiO2 as a highly performant photocatalyst maximized by proper parameters selection

The synthesis and characterization of novel graphene oxide coupled to TiO2 (GO-TiO2) was carried out in order to better understand the performance of this photocatalyst, when compared to well-known TiO2 (P25) from Degussa. Thus, its physical-chemical characterization (FTIR, XRD, N2 isotherms and electrochemical measurements) describes high porosity, suitable charge and high electron mobility, which enhance pollutant degradation. In addition, the importance of the reactor set up was highlighted, testing the effect of both the irradiated area and distance between lamp and bulb solution. Under optimal conditions, the model drug methylthioninium chloride (MC) was degraded and several parameters were assessed, such as the water matrix and the catalyst reutilization, a possibility given the addition of H2O2. The results in terms of energy consumption compete with those attained for the treatment of this model pollutant, opening a path for further research.Xunta de Galicia | Ref. ED481B 2019/091Ministerio de Ciencia e Innovación | Ref. PID2020-113667GB-I0

Structured organic frameworks as endocrine disruptor adsorbents suitable for Fenton regeneration and reuse

New porous materials, such as metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs), have been actively investigated due to their environmental applications. In this study, four of such structured materials, namely Fe3O4 @COF, MIL-53(Al), MIL-53(Al)-F127 and NH2-MIL-101(Fe) were synthetized. These materials have been tested for the first time for the adsorption in aqueous media of two endocrine disruptor pollutants, bisphenol A (BPA) and prednisolone (PDN). The adsorbents were characterized by the analysis of the point of zero charge (PZC), the functional groups (FTIR) and their physic-chemical structure (N2-isotherms, SEM, XRD and XPS). MIL-53-Al provided the highest uptake of both BPA (177.78 mg g− 1) and PDN (280.70 mg g− 1) even when using a real wastewater matrix. Additionally, this MOF resulted to be a so-called catalytic-adsorbent, maintaining an appropriate adsorbent capacity after five regenerations cycles via Fenton-like process, causing only 20% and 5% adsorption detriment for BPA and PDN, respectively. This avoids spent adsorbent disposal issues and make this new kind of adsorbent to have the potential to be used in real environmental application scenarios.Agencia Estatal de Investigación | Ref. PID2020-113667GB-I00Agencia Estatal de Investigación | Ref. PDC2021-121394-I00Xunta de Galicia | Ref. ED481D-2023/015Universidade de Vigo/CISU

Fluoride-doped TiO2 photocatalyst with enhanced activity for stable pollutant degradation

Fluoride-doped TiO2 (F-TiO2) was synthesized by an efficient and simple one-step synthesis and successfully used for the UV-photo-degradation of the toxic and stable pollutants methylene blue (MB) and bisphenol A (BPA). Initially, the synthesized catalyst was characterized and compared to untreated TiO2 (P25 Degussa) by different physical–chemical analyses such as XRD, band gap calculation, SEM, EDS, FITR, ECSA, or EIS. F-TiO2 defeated commercial TiO2, and almost complete pollutant removal was achieved within 30 min. The energy consumption was reduced as a result of the suitable reactor set-up, which reduced light scattering, and by the application of a long-pulse radiation procedure, where the lamp was switched off during periods where the radical degradation continued. This enhanced the overall photocatalysis process performance. Under these conditions, 80% of MB removal was attained within 15 min radiation with an energy consumption of only 0.070 Wh min−1, demonstrating a much better efficiency when compared to previously reported data. The catalyst was reusable, and its performance can be improved by the addition of H2O2. The results were validated by BPA degradation and the treatment of real wastewaters with both pollutants. The results were so encouraging that a scale-up reactor has been proposed for future studies.Xunta de Galicia | Ref. ED481B 2019/091Xunta de Galicia | Ref. ED431C 2021-43Ministerio de Ciencia e Innovación | Ref. PCI2022-132941Ministerio de Ciencia e Innovación | Ref. PID2020- 113667GB-I0

Electrocatalytic performance and stability of nanostructured Fe–Ni pyrite-type diphosphide catalyst supported on carbon paper

A simple and effective method to prepare an active and stable nanostructured working electrode for electrochemical water splitting is described. Specifically, mixed Fe–Ni diphosphide was prepared by sputtering a 200-nm-thick layer of Permalloy onto carbon paper gas diffusion layer followed by gas transport phosphorization reaction. The mass density of the resultant diphosphide phase was established to be 1.1 mg/cm2. Energy-dispersive X-ray microanalysis shows that the actual elemental composition of the resultant ternary electrocatalyst is approximately Fe0.2Ni0.8P2, while the powder X-ray diffraction analysis confirms that the electrocatalyst crystallizes in NiP2 cubic pyrite-like structure. As a cathode for hydrogen evolution reaction (HER) in acidic and alkaline electrolytes, this earth-abundant electrode has exchange current densities of 6.84103 and 3.16103 mA/cm2 and Tafel slopes of 55.3 and 72.2 mV/dec, respectively. As an anode for oxygen evolution reaction (OER) in alkaline electrolyte, the electrode shows an exchange current density of 2.88104 mA/cm2 and Tafel slope of 49.3 mV/dec. The observed high activity of the electrode correlates well with its electronic structure, which was assessed by density functional theory (DFT) calculations. The stability of Fe0.2Ni0.8P2 electrocatalyst in HER and OER was evaluated by means of accelerated degradation test and chronopotentiometry. The results of these experiments elucidate partial dissolution and entire chemical transformation of Fe0.2Ni0.8P2 as the main mechanisms of the electrode degradation during HER and OER, respectively. Overall, our findings could facilitate the composition-based design of active, stable, and durable phosphide electrodes for electrochemical water splitting.We thank all members of the Nanomaterials Synthesis Unit at the INL for their fruitful scientific and technical input, as well as Dr. X. Wang for his help with the electrocatalytic data analysis. This investigation has benefited from the financial support provided by the European Union Horizon 2020 NMP programme through the CritCat project under grant agreement no. 686053, as well as ERDF funds through the Portuguese Operational Programme for Competitiveness and Internationalization (COMPETE 2020), and National Funds through the Portuguese Foundation for Science and Technology (FCT), under the PrintPV project PTDC/CTM-ENE/5387/2014 (grant agreement no. 016663). J.D.C. thanks the FCT PhD grant SFRH/BD/79393/2011, while J.L.L. thanks Marie-Curie-ITN607904-SPINOGRAPH project for the PhD grant