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Proton exchange membrane fuel cells have been recently developed at an increasing pace as clean energy conversion devices for stationary and transport sector applications. High platinum cathode loadings contribute significantly to costs. This is why improved catalyst and support materials as well as catalyst layer design are critically needed. Recent advances in nanotechnologies and material sciences have led to the discoveries of several highly promising families of materials. These include platinum-based alloys with shape-selected nanostructures, platinum-group-metal-free catalysts such as metal-nitrogen-doped carbon materials and modification of the carbon support to control surface properties and ionomer/catalyst interactions. Furthermore, the development of advanced characterization techniques allows a deeper understanding of the catalyst evolution under different conditions. This review focuses on all these recent developments and it closes with a discussion of future research directions in the field. The high platinum loadings at the cathodes of proton exchange membrane fuel cells significantly contribute to the cost of these clean energy conversion devices. Here, the authors critically review and discuss recent developments on low- and non-platinum-based cathode catalysts and catalyst layers.

NiFe and CoFe (MFe) layered double hydroxides (LDHs) are among the most active electrocatalysts for the alkaline oxygen evolution reaction (OER). Herein, we combine electrochemical measurements, operando X-ray scattering and absorption spectroscopy, and density functional theory (DFT) calculations to elucidate the catalytically active phase, reaction center and the OER mechanism. We provide the first direct atomic-scale evidence that, under applied anodic potentials, MFe LDHs oxidize from as-prepared α-phases to activated γ-phases. The OER-active γ-phases are characterized by about 8% contraction of the lattice spacing and switching of the intercalated ions. DFT calculations reveal that the OER proceeds via a Mars van Krevelen mechanism. The flexible electronic structure of the surface Fe sites, and their synergy with nearest-neighbor M sites through formation of O-bridged Fe-M reaction centers, stabilize OER intermediates that are unfavorable on pure M-M centers and single Fe sites, fundamentally accounting for the high catalytic activity of MFe LDHs. NiFe and CoFe layered double hydroxides are among the most active electrocatalysts for the alkaline oxygen evolution reaction. Here, by combining operando experiments and rigorous DFT calculations, the authors unravel their active phase, the reaction center and the catalytic mechanism.

Powered by renewable energy sources such as solar, marine, geothermal and wind, generation of storable hydrogen fuel through water electrolysis provides a promising path towards energy sustainability. However, state-of-the-art electrolysis requires support from associated processes such as desalination of water sources, further purification of desalinated water, and transportation of water, which often contribute financial and energy costs. One strategy to avoid these operations is to develop electrolysers that are capable of operating with impure water feeds directly. Here we review recent developments in electrode materials/catalysts for water electrolysis using low-grade and saline water, a significantly more abundant resource worldwide compared to potable water. We address the associated challenges in design of electrolysers, and discuss future potential approaches that may yield highly active and selective materials for water electrolysis in the presence of common impurities such as metal ions, chloride and bio-organisms. Production of hydrogen fuel by electrolysis of low-grade or saline water, as opposed to pure water, could have benefits in terms of resource availability and cost. This Review examines the challenges of this approach and how they can be addressed through catalyst and electrolyser design.

Morphological shape in chemistry and biology owes its existence to anisotropic growth and is closely coupled to distinct functionality. Although much is known about the principal growth mechanisms of monometallic shaped nanocrystals, the anisotropic growth of shaped alloy nanocrystals is still poorly understood. Using aberration-corrected scanning transmission electron microscopy, we reveal an element-specific anisotropic growth mechanism of platinum (Pt) bimetallic nano-octahedra where compositional anisotropy couples to geometric anisotropy. A Pt-rich phase evolves into precursor nanohexapods, followed by a slower step-induced deposition of an M-rich (M = Ni, Co, etc.) phase at the concave hexapod surface forming the octahedral facets. Our finding explains earlier reports on unusual compositional segregations and chemical degradation pathways of bimetallic polyhedral catalysts and may aid rational synthesis of shaped alloy catalysts with desired compositional patterns and properties.

This contribution reports the discovery and analysis of a p -block Sn-based catalyst for the electroreduction of molecular oxygen in acidic conditions at fuel cell cathodes; the catalyst is free of platinum-group metals and contains single-metal-atom actives sites coordinated by nitrogen. The prepared SnNC catalysts meet and exceed state-of-the-art FeNC catalysts in terms of intrinsic catalytic turn-over frequency and hydrogen–air fuel cell power density. The SnNC-NH 3 catalysts displayed a 40–50% higher current density than FeNC-NH 3 at cell voltages below 0.7 V. Additional benefits include a highly favourable selectivity for the four-electron reduction pathway and a Fenton-inactive character of Sn. A range of analytical techniques combined with density functional theory calculations indicate that stannic Sn( iv )N x single-metal sites with moderate oxygen chemisorption properties and low pyridinic N coordination numbers act as catalytically active moieties. The superior proton-exchange membrane fuel cell performance of SnNC cathode catalysts under realistic, hydrogen–air fuel cell conditions, particularly after NH 3 activation treatment, makes them a promising alternative to today’s state-of-the-art Fe-based catalysts. For oxygen reduction and hydrogen oxidation reactions, proton-exchange membrane fuel cells typically rely on precious-metal-based catalysts. A p -block single-metal-site tin/nitrogen-doped carbon is shown to exhibit promising electrocatalytic and fuel cell performance.

Octahedra (oh) PtNiX/C catalysts have attracted attention as cathode catalysts for proton-exchange membrane fuel cells (PEMFCs) due to their exceptional catalytic activities toward the oxygen reduction reaction. Here, we investigate the degradation dynamics of oh-PtNiIr in fuel cell conditions by operando X-ray diffraction (XRD). Two XRD-coupled square-wave accelerated stress tests (0.6 to 0.95) V and (0.7 to 0.95) V (where V is the cell voltage) confirm that, when fixing the upper limit, the dissolution and overall degradation strongly depend on the lower potential limit. By directly observing the extent of metal oxidation during potential cycling, we link the alloy redox dynamics to the stability. The studied catalysts' stability is proportional to both the extent of metal oxidation and, more interestingly, the degree of reduction. Comparing a benchmark Pt catalyst with oh-PtNiIr allows for associating the differences between oxidation and reduction potentials and the optimal usage window for each class of catalysts. This relatively simple method can be employed to find the operation boundaries of the PEMFC to minimize the degradation of a large class of Pt-based catalysts without time-consuming stress tests.

A task force of the United Italian society of Endocrine Surgery (SIUEC) was commissioned to review the position statement on diagnostic, therapeutic and health‑care management protocol in thyroid surgery published in 2016, at the light of new technologies, recent oncological concepts, and tailored approaches. The objective of this publication was to support surgeons with modern rational protocols of treatment that can be shared by health-care professionals, taking into account important clinical, healthcare and therapeutic aspects, as well as potential sequelae and complications. The task force consists of 13 members of the SIUEC highly trained and experienced in thyroid surgery. The main topics concern clinical evaluation and preoperative workup, patient preparation for surgery, surgical treatment, non-surgical options, postoperative management, prevention and management of major complications, outpatient care and follow-up.

PurposeRadical eradication of deep infiltrating endometriosis (DIE) is associated with a high risk of iatrogenic autonomic denervation and pelvic dysfunction. Our aim was to prospectively analyze peri-operative details and post-operative functional outcomes (in terms of pain relief and bladder, rectal, and sexual function) among women operated for DIE of the posterior compartment with nerve-sparing technique, using the visual analogue scale and validated questionnaires.MethodsAll women undergoing laparoscopic nerve-sparing eradicative surgery for DIE nodules of the posterior compartment ≥ 4 cm ± bowel resection were included. Pain scores [using Visual Analogue Scale (VAS) scores] were collected before surgery and 6 and 12 months after surgery. Functional outcomes in terms of bladder, rectal, and sexual function, were evaluated using validated questionnaires (i.e., ICIQ-UISF, NBD score, and FSFI) administered pre-operatively and 6 months after surgery.Main resultsA total of 34 patients were included. Twenty-eight (82.4%) of them had already undergone a previous abdominal surgery for endometriosis. Bowel resection was performed in 16 (47.1%) patients. Median VAS score levels of pelvic pain were significantly decreased after surgery both at 6 (median 3, range 0–7 and 2, 0–7, respectively) and at 12 months (3, 0–8 and 2, 0–7), compared to pre-operative levels (9, 1–10 and 3, 0–7, respectively) (p < 0.0001). No differences were found in terms of urinary function between pre- and post-operative ICIQ-SF questionnaires. In no cases, bladder self-catheterization was needed at the 6-and 12-month follow-up. Median NBD score was 3.5 (0–21) pre-operatively and 2 (0–18) after 6 months (p = 0.72). The pre-operative total FSFI score was 19.1 (1.2–28.9) vs. 22.7 (12.2–31) post-operatively (p = 0.004).ConclusionsThe nerve-sparing approach is effective in eradicating DIE of the posterior compartment, with satisfactory pain control, significant improvement of sexual function, and preservation of bladder and rectal function.