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Operando examination of reaction intermediates during (photo)-electrocatalytic processes, particularly with respect to their kinetics, is a critical but challenging task. Spectroelectrochemical (SEC) methods based on UV-vis spectroscopy offer potential insights into intermediate species, although they are often applied under steady-state conditions. In this work, we employ excitation-modulated absorption spectroscopy (EMAS), which utilizes periodic modulation of either potential or light intensity, to dynamically probe the SEC responses of a hematite (FeO) photoanode, NiFeO -type electrocatalysts, and their composites. Comparison of spectral profiles in the frequency domain under electrocatalytic (EC) and photoelectrocatalytic (PEC) conditions allows for the identification of key reaction intermediates and their corresponding redox rate constants, which further facilitates the revelation of key steps of charge dynamics. Specifically, EC and PEC water oxidation on bare FeO photoanodes proceed via the same reaction intermediate Fe-(IV) with similar kinetics. For composite hematite photoanodes, a faster redox rate of the oxidized catalytic reaction intermediates of the electrocatalyst upon accepting holes from the semiconductor is crucial for achieving a high photocurrent density. These results highlight EMAS as a powerful and versatile tool to understand (photo)-electrocatalytic systems.
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http://dx.doi.org/10.1021/jacsau.5c00131 | DOI Listing |
J Am Chem Soc
September 2025
Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States.
Alternating current (AC) electrolysis offers a promising strategy for modulating redox states in metal-catalyzed reactions, yet its mechanistic basis remains poorly understood. Here, we uncover how AC frequency synchronizes with key steps in a Ni-catalyzed cross-coupling cycle to control product selectivity between C-N and C-C coupling. We show that optimal C-N selectivity arises from minimizing the exposure of a key intermediate, Ni(Ar)Br, to reducing conditions that otherwise promote off-cycle Ni species and undesired C-C homocoupling.
View Article and Find Full Text PDFJ Org Chem
September 2025
Collaborative Innovation Center of Henan Province for Green Manufacturing of Fine Chemicals, Key Laboratory of Green Chemical Media and Reactions, Ministry of Education, Henan Key Laboratory of Organic Functional Molecule and Drug Innovation, School of Chemistry and Chemical Engineering, Henan Norma
Internucleoside guanidinium linkages are excellent mimics of phosphodiesters and have been used to improve the properties of oligonucleotides. Herein we reported a step economic bimolecular simultaneous macrocyclization (BSM) protocol to prepare cyclic dinucleotide (CDN) analogues with guanidinium linkages. Compared with the 26 steps protocol reported in literature, the current method could provide CDN analogues with internucleoside guanidinium linkages in 9 steps, and the key intermediate prepared in the first 3 steps could be shared to prepare CDN analogues with different nucleobases.
View Article and Find Full Text PDFOrg Lett
September 2025
Hubei Key Laboratory of Pollutant Analysis & Reuse Technology, College of Chemistry and Chemical Engineering, Hubei Normal University, Huangshi 435002, P. R. China.
A regioselective C3-H alkynylation of triazolopyridazines has been achieved via dual gold/silver catalysis employing hypervalent iodine(III) reagents. The transformation proceeds through an alkynyl Au(III) intermediate and a silver-assisted C-H activation pathway, delivering a broad range of 3-alkynylated triazolopyridazines in good to excellent yields. Mechanistic studies, including H/D exchange experiments, reveal that the silver species plays a crucial role in facilitating C-H activation.
View Article and Find Full Text PDFJ Phys Chem A
September 2025
Department of Chemistry, Tsinghua University, Beijing 100084, China.
A series of Cu-based single-atom catalysts (SACs) with asymmetric coordination were designed to accelerate lithium-sulfur (Li-S) chemistry. The electronegativity contrast from the dopant induces a localized electronic asymmetry that amplifies Jahn-Teller distortion at the Cu center. This distortion profoundly modulates the Cu 3d electronic structure and its interaction with Li-S intermediates.
View Article and Find Full Text PDFDiscov Nano
September 2025
Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, 30013, Taiwan.
Promoter-assisted chemical vapor deposition (CVD) has emerged as a robust strategy for the low-temperature synthesis of diverse transition metal dichalcogenides (TMDs). In these processes, promoter-induced intermediates facilitate specific reaction pathways, enabling controlled growth via vapor-solid-solid (VSS) or vapor-liquid-solid (VLS) modes. While previous studies have primarily focused on transition metal precursors, growth pathways involving engineered chalcogen-based intermediates remain underexplored due to their volatility and low melting points.
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