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Keywords: carbon dioxide reduction; cuprous oxide; scanning electrochemical microscopy; Raman microscopy; in situ characterization EN carbon dioxide reduction cuprous oxide scanning electrochemical microscopy Raman microscopy in situ characterization 1 1 1 02/21/22 20220211 NES 220211 B The Cover Feature b illustrates the simultaneous probing of a cuprous oxide microcrystal by Raman and Scanning Electrochemical Microscopy (SECM) during CO SB 2 sb electro-reduction. Cover Feature: Probing Individual Cuprous Oxide Microcrystals towards Carbon Dioxide Reduction by using In Situ Raman-coupled Scanning Electrochemical Microscopy (ChemElectroChem 3/2022) Carbon dioxide reduction, cuprous oxide, scanning electrochemical microscopy, Raman microscopy, in situ characterization. [Extracted from the article]

The electrochemical carbon dioxide reduction reaction (CO2RR) over carbon-supported gold nanoparticles (AuNP) was investigated using a broad variety of (electro)analytical methods, including linear sweep voltammetry with a rotating disk electrode (LSV-RDE), sample-generation tip-collection mode of scanning electrochemical microscopy (SG/TC-SECM), as well as full cell tests with highly sensitive online gas chromatography (GC). In contrast to most other studies, this work focuses on the low-overpotential region (0 to -0.4 V vs RHE) where initial product formation is already detected and addresses micro- to macro-sized electrodes. The sub-10 nm AuNPs supported on three different carbon supports (CNTs and carbon blacks) were pretreated in H 2 /Ar to remove the stabilizer used during AuNP synthesis. LSV-RDE points toward different CO2RR mechanisms at the samples, additionally confirmed by the SG/TC-SECM and full cell tests with online GC. Besides H 2 and CO, the AuNP supported on carbon nanotubes showed significant evolution of H 2 CO in contrast to the other two samples, which was additionally confirmed by accumulating the product during chronoamperometric RDE experiments followed by mass spectroscopic analysis. Surface analysis indicated a complete removal of residual thiolate stabilizer molecules exclusively at the AuNPs supported on carbon nanotubes, which may result in a change in the adsorption geometry or reaction mechanism at this sample. The results demonstrate the effectiveness of the combination of these multiple methods to investigate the CO2RR in the low-overpotential region.

We report on the new Ruddlesden-Popper (RP) oxyfluoride La 2 NiO 2.5 F 3 containing an unprecedented high amount of fluorine and Ni 2+ . This oxyfluoride was prepared by topochemical low-temperature fluorination of La 2 NiO 4 , which was obtained by a soft chemistry synthesis, with poly(vinylidene difluoride) (PVDF) as fluorinating agent. La 2 NiO 2.5 F 3 is the first n = 1 RP compound crystallizing in the tetragonal space group P 4 2 / nnm ( a = 5.7297(6) Å and c = 13.0106(2) Å). The crystal structure shows a unique tilting scheme of the NiO 4 F 2 octahedra that has so far been only theoretically predicted. Combined neutron and X-ray powder diffraction experiments together with bond-valence-sum and DFT+U calculations reveal an unusual anion ordering with fluoride being located on the apical anion sites of the NiO 4 F 2 octahedra. Excess fluorine ions were found to populate two of the four interstitial anion sites in an ordered fashion. A third interstitial anion position is occupied by oxygen ions while the fourth site remains unoccupied. This hitherto unobserved ordering scenario in RP oxyfluorides promotes a strong layerwise alternating tilting of the NiO 4 F 2 octahedra. Magnetic measurements show strong antiferromagnetic interactions with a high Néel temperature of about 225 K and a pronounced ZFC/FC splitting most likely as the result of a small ferromagnetic moment arising from spin canting. The electronic structure was characterized by DFT and UV-vis spectroscopy, and a strong increase of E g was found compared to La 2 NiO 4 (3.4 eV vs 1.3 eV).