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Voltage reversal is a severe issue in proton exchange membrane fuel cells (PEMFCs), which can be overcome by adding oxygen evolution electrocatalysts (OER) based on iridium oxide (IrO X ) to the anode catalyst layer. However, the crystal structure and antireversal properties of such anode materials have been rarely investigated. Herein, we report amorphous IrO X and explore the transformation of crystal structure under heat treatment to examine their antireversal performance in PEMFCs. It is found that heat treatment results in larger catalyst particles which consequences lower OER activity; however, it shows better voltage reverse tolerance (132.2 min). These investigations demonstrate that a balance is crucial between activity and durability in antireversal properties for PEMFCs. Physical characterizations reveal that improved stability and reversal tolerance is attributed to crystallinity and preferred orientation of IrO X crystals as well as existence of amorphous and crystalline IrO X . This work proposes a attempt to use the mixed phase IrO X in the antireversal anode catalyst and highlights the role of corresponding particle size and durability characteristics for the long-term durability of PEMFCs.

Voltage reversal of proton exchange membrane fuel cells caused by hydrogen deficiency seriously deteriorates the anodes and lowers their performance and lifetime. A commonly used method is to add oxygen evolution reaction catalysts (e.g., IrO 2 ) to the anode to extend the water electrolysis plateau against harmful carbon corrosion. Herein, strongly connected IrO x nanoparticles (SC-IrO x ) are prepared by removing the low surface area carbon carrier of the as-synthesized Ir/C catalyst. The reversal-tolerant anode with SC-IrO x owns an anti-reversal time of 9.32 h, which is 3.2 and 4.4 times that of the reversal-tolerant anode with commercial IrO x and weakly connected IrO x , respectively. Further transmission electron microscope characterizations reveal that SC-IrO x can construct a stable electron and proton transport pathway in the anode catalyst layer, which can delay the isolation of oxygen evolution reaction catalyst from the electron and proton conducting network, thus extending the water electrolysis plateau. Herein, our findings suggest that tuning the microstructures of IrO x catalysts is indeed an effective and promising approach to extend the water electrolysis plateau and alleviate the performance degradation of proton exchange membrane fuel cells during the voltage reversal process.

Ammonia (NH 3 ) is one of the hydrogen carriers that has received extensive attention due to its high hydrogen content and carbon-free nature. The ammonia electro-oxidation reaction (AOR) and the liquid AOR (LAOR) are integral parts of an ammonia-based energy system. The exploration of low-cost and efficient electrocatalysts for the AOR and LAOR is very important but very difficult. In this work, a novel self-supporting AOR and LAOR bifunctional electrocatalyst of a Ag 3 CuS 2 film is synthesized by a simple hydrothermal method. The Ag 3 CuS 2 film without a substrate shows efficient catalytic activity and enhanced stability for NH 3 electrolysis in both aqueous ammonia solution and liquid ammonia, including an onset potential of 0.7 V for the AOR and an onset potential of 0.4 V for the LAOR. The density functional theory calculations prove that compared to Cu atoms, Ag atoms with appropriate charge density on the surface of Ag 3 CuS 2 are more electrocatalytically active for NH 3 splitting, including the low energy barrier in the rate-determining *NH 3 dehydrogenation step and the spontaneous tendency in the N 2 desorption process. Overall, the foamed Ag 3 CuS 2 film is one of prospective low-cost and stable electrocatalysts for the AOR and LAOR, and the self-supporting strategy without a substrate provides more perspectives to tailor more meaningful and powerful electrocatalysts.

The aim of this study is to establish a new method with high sensitivity, accuracy, and stability for the determination of human IgG and then expand it to analyze severe acute respiratory syndrome corona virus 2 (SARS-CoV-2)-specific IgM and IgG, which is of great significance for the screening and diagnosis of COVID-19. In this study, the magnetic Fe 3 O 4 nanospheres coupled with mouse antihuman IgG (Ab1 IgG ) were used as an immune capture probe (Fe 3 O 4 @Ab1 IgG ) to capture and separate the target, and rabbit antihuman IgG (Ab2 IgG ) coupled with highly luminescent quantum dot nanobeads (QBs) as a fluorescence detection probe (QBs@Ab2 IgG ) was used to realize high sensitivity detection. After the formation of a sandwich immunocomplex, the fluorescence intensity of the precipitate after magnetic separation was measured at the excitation wavelength of 370 nm. Under optimal conditions, a wide linear range varying from 0.005 to 40 ng·mL -1 was obtained for the detection of human IgG with a lower limit of detection at 4 pg·mL -1 (S/N = 3). The recoveries of intra- and interassays were 90.0-101.9 and 96.0-106.6%, respectively, and the relative standard deviations were 6.3-10.2 and 2.6-10.5%, respectively. Furthermore, the proposed method was successfully demonstrated to detect human IgG in serum samples, and the detection results were not statistically different ( P > 0.05) from commercial enzyme-linked immunosorbent assay kits. This method is sensitive, fast, and accurate, which could be expanded to detect the specific IgM and IgG antibodies against SARS-CoV-2., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

Chloroethylnitrosoureas (CENUs) are an important type of alkylating agent employed in the clinical treatment of cancer. However, the anticancer efficacy of CENUs is greatly decreased by a DNA repairing enzyme, O 6 -alkylguanine-DNA alkyltransferase (AGT), by preventing the formation of interstrand cross-links (ICLs). In this study, a combi-nitrosourea prodrug, namely, N -(2-chloroethyl)- N '-2-(O 6 -benzyl-9-guanine)ethyl- N -nitrosourea (BGCNU), which possesses an O 6 -benzylguanine (O 6 -BG) derivative and CENU pharmacophores simultaneously, was synthesized and evaluated for its ability to induce ICLs. The target compound is markedly more cytotoxic in human glioma cells than the clinically used CENU chemotherapies ACNU, BCNU, and their respective combinations with O 6 -BG. In the AGT-proficient cells, significantly higher levels of DNA ICLs were observed in the groups treated by BGCNU than those by ACNU and BCNU, which indicated that the activity of AGT was effectively inhibited by the O 6 -BG derivatives released from BGCNU., Competing Interests: The authors declare no competing financial interest.