Language：English   Publisher：Angewandte Chemie International Edition  

Electrocatalytic carbon dioxide (CO<inf>2</inf>) reduction reaction (CO<inf>2</inf>RR) has emerged as a promising strategy for sustainable energy conversion and carbon utilization. Despite intensive research efforts, the understanding of intermediates and pathways leading from CO<inf>2</inf>RR to multicarbon (C<inf>2+</inf>) chemicals remains incomplete. The challenge is to gain insight into the activation of adsorbed CO and the subsequent pathways. Here, we design a specially tailored Cu nanowire array facing a hydrophobic interface as an electrode to highly enhance Raman signals in the in situ environment, allowing sensitive observation of the sequential change of various elusive intermediates during CO<inf>2</inf>RR, such as CO, CH<inf>2</inf>, CO coexisting with CH<inf>2</inf>, CH<inf>2</inf>CO, and CH<inf>3</inf>. Density functional theory calculations reveal that the C─C coupling during CO<inf>2</inf>RR originates from an asymmetric coupling between CH<inf>2</inf> and CO to form CH<inf>2</inf>CO, identified as the rate-determining step in the formation of C<inf>2+</inf> products. These findings deepen the understanding of the C─C coupling processes, which are crucial for advancing catalyst development in electrochemical CO<inf>2</inf> upgrading.

DOI： 10.1002/anie.202502740

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PubMed

Language：English   Publisher：ACS Applied Materials and Interfaces  

CO2 electroreduction (eCO2R) holds promise as an environmentally friendly approach to reducing greenhouse gas emissions. Cu is a representative catalyst with high eCO2R activity. However, its selectivity for CH4 synthesis is still insufficient due to the slow eight-electron transfer to a single carbon, the predominance of C-C coupling reactions toward C2+ products on Cu, as well as occurrence of the hydrogen evolution reaction. Here, for high CH4 selectivity, we demonstrate a genuine hydrogen supply to atomically dispersed Cu sites (AD-Cu) via the cooperative function of oxygen vacancy (VO) formed on defective black anatase TiO2 (Cu-TiO2-H2), that is prepared by exposing Cu-doped TiO2 (Cu-TiO2) to hydrogen gas. Cu-TiO2-H2 exhibited a remarkable Faradaic efficiency for CH4 production of 63% and a partial current density of −120 mA cm-2. The catalytic mechanism for the high CH4 selectivity was elucidated using a variety of spectroscopies, such as electron spin resonance, reversed double-beam photoacoustic spectroscopy (RDB-PAS) and in situ Raman measurements, with the support of quantum chemical calculations. In situ Raman measurements revealed that Cu-TiO2-H2 greatly accelerates proton consumption for the hydrogenation of *CO intermediates and that the surface pH on Cu-TiO2-H2 is sufficiently high to stabilize *CHO intermediates, key species for CH4 formation. DFT calculations support the stability of the intermediates during the process of forming *CHO. All our results suggest that VO contiguous to AD-Cu on Cu-TiO2-H2 promotes water dissociation and smoothly supplies hydrogen to AD-Cu on Cu-TiO2-H2, thus facilitating CH4 formation in eCO2R.

DOI： 10.1021/acsami.5c00484

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PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Journal of the American Chemical Society  

Metal-organic framework (MOF) glasses have emerged as a new class of organic-inorganic hybrid glass materials. Considerable efforts have been devoted to unraveling the macroscopic dynamics of MOF glasses by studying their rheological behavior; however, their microscopic dynamics remain unclear. In this work, we studied the effect of vitrification on linker dynamics in ZIF-62 by solid-state 2H nuclear magnetic resonance (NMR) spectroscopy. 2H NMR relaxation analysis provided a detailed picture of the mobility of the ZIF-62 linkers, including local restricted librations and a large-amplitude twist; these details were verified by molecular dynamics. A comparison of ZIF-62 crystals and glasses revealed that vitrification does not drastically affect the fast individual flipping motions with large-amplitude twists, whereas it facilitates slow cooperative large-amplitude twist motions with a decrease in the activation barrier. These observations support the findings of previous studies, indicating that glassy ZIF-62 retains permanent porosity and that short-range disorder exists in the alignment of ligands because of distortion of the coordination angle.

DOI： 10.1021/jacs.3c13156

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PubMed

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Book type：Scholarly book

DOI： 10.1007/978-981-99-7062-9