Electrocatalysis plays a prominent role in the development of carbon dioxide utilisation technologies. Many new and improved CO₂ conversion catalysts have been developed in recent years, progressively achieving better performance. However, within this flourishing field, a disconnect in catalyst performance evaluation has emerged as the Achilles heel of CO₂ electrolysis. Too often, catalysts are assessed in electrochemical settings that are far removed from industrially relevant operational conditions, where CO₂ mass transport limitations should be minimised. To overcome this issue, gas diffusion electrodes and gas-fed electrolysers need to be developed and applied, presenting new challenges and opportunities to the CO₂ electrolysis community. In this review, we introduce the reader to the fundamentals of gas diffusion electrodes and gas-fed electrolysers, highlighting their advantages and disadvantages. We discuss in detail the design of gas diffusion electrodes and their operation within gas-fed electrolysers in both flow-through and flow-by configurations. Then, we correlate the structure and composition of gas diffusion electrodes to the operational performance of electrolysers, indicating options and prospects for improvement. Overall, this study will equip the reader with the fundamental understanding required to enhance and optimise CO₂ catalysis beyond the laboratory scale.

Phosphorene is a new two-dimensional material which is commonly prepared by exfoliation from black phosphorus bulk crystals that historically have been synthesized from white phosphorus under high-pressure conditions. The few layers of phosphorene have a direct band gap in the range of 0.3–2 eV and high mobility at room temperature comparable to epitaxial graphene. These characteristics can be used for the design of high speed digital circuits, radio frequency circuits, flexible and printed systems, and optoelectronic devices. In this work, we synthesized black phosphorus from red phosphorus, which is a safer solid precursor, using sonochemistry. Furthermore, via a variety of microscopy and spectroscopy techniques, we report characterization results of the sonochemically synthesized black phosphorus in addition to the commercial black phosphorus. Finally, we describe the air stability of black phosphors and the crystalline structure of the synthesized material. This is the first result of sonochemical or solution-based synthesis of black phosphorus based on readily available low-cost red phosphorus. This solution-based synthesis of black phosphorus is suitable for printable applications of nanomaterial.

We report for the first time a procedure in which Nafion/Graphite nanoplatelets (GNPs) thin films are fabricated using a modified layer-by-layer (LbL) method. The method consists of dipping a substrate (quartz and/or glassy carbon electrodes) into a composite solution made of Nafion and GNPs dissolved together in ethanol, followed by washing steps in water. This procedure allowed the fabrication of multilayer films of (Nafion/GNPs)_n by means of hydrogen bonding and hydrophobic‒hydrophobic interactions between Nafion, GNPs, and the corresponding solid substrate. The average thickness of each layer evaluated using profilometer corresponds to ca. 50 nm. The as-prepared Nafion/GNPs LbL films were characterized using various spectroscopic techniques such as X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), FTIR, and optical microscopy. This characterization highlights the presence of oxygen functionalities that support a mechanism of self-assembly via hydrogen bonding interactions, along with hydrophobic interactions between the carbon groups of GNPs and the Teflon-like (carbon‒fluorine backbone) of Nafion. We showed that Nafion/GNPs LbL films can be deposited onto glassy carbon electrodes and utilized for the voltammetric detection of caffeine in beverages. The results showed that Nafion/GNPs LbL films can achieve a limit of detection for caffeine (LoD) of 0.032 μM and linear range between 20‒250 μM using differential pulse voltammetry, whereas, using cyclic voltammetry LoD and linear range were found to be 24 μM and 50‒5000 μM, respectively. Voltammetric detection of caffeine in beverages showed good agreement between the values found experimentally and those reported by the beverage producers. The values found are also in agreement with those obtained using a standard spectrophotometric method. The proposed method is appealing because it allows the fabrication of Nafion/GNPs thin films in a simple fashion using a single-step procedure, rather than using composite solutions with opposite electrostatic charge, and also allows the detection of caffeine in beverages without any pre-treatment or dilution of the real samples. The proposed method is characterized by a fast response time without apparent interference, and the results were competitive with those obtained with other materials reported in the literature.

Oxygen depolarised cathode technology in support of achieving CO₂ gas diffusion electrodes industrial performance.

Disposable electronic cigarettes (ECs), also commonly known as vapes, have gained increasing popularity, particularly among young users, due to their accessibility and variety of flavours. Although the constituents of refill- able tank-style and cartridge-based EC devices have been studied, only a limited amount of data is currently avail- able for disposable or single-use ECs. In this study, the chemicals of 60 disposable ECs have been investigated, including different flavours and brands. Ethyl maltol and benzoic acid were quantified across various e-liquid flavours, brands and nicotine concentrations from disposable ECs. The chemical composition changes with EC usage were also investigated, comparing new and used disposable ECs. Headspace gas chromatography/mass spectrometry was employed to identify and quantify the chemicals. 89 % of the analysed EC liquids presented ethyl maltol, where 42 % of them presents 10 times higher concentrations than the ones set by the General Standard for Food Additives and 88 % of them exceed the concentration previously reported as cytotoxic. 87 % of the investigated EC fluids contained benzoic acid, where 71 % of them exceeded 20 times the values reported as genotoxic in human lymphocytes. Our results support the link between benzoic acid and nicotine contain and provide new information regarding the concentration changes within flavours and suppliers. Both chemicals have shown similar patterns through usage, presenting an increase of concentration between 40 and 80 puff. Our study demonstrates the need of maintaining constant oversight of e-liquids, as they are continuously changing in often subtle but toxicologically detrimental ways.