Direct Observation of Active Nickel Oxide Cluster in Nickel–Borate Electrocatalyst for Water Oxidation by In Situ O K‑Edge X‑ray Absorption Spectroscopy

In situ O K-edge X-ray absorption fine structure (XAFS) spectroscopy was applied to investigate the electronic and structural change in the nickel–borate (Ni–B_i) electrocatalyst during the oxygen evolution reaction (OER). An absorption peak was observed around 528.7 eV at 1.0 V versus Ag/AgCl in a potassium borate aqueous solution, which relates with the formation of nanoscale order domains of edge-sharing NiO₆ octahedra in the Ni–B_i electrocatalyst. XAFS spectra were measured with variation of the electrode potential from 0.3 up to 1.0 V. The measured absorption peaks suggest that the quantity of NiO₆ octahedra increased in correlation with the OER current; however, when the potential was changed downward, the XAFS absorption peak assigned to NiO₆ octahedra remained constant, even at the electrode potential for no OER current. This difference implies that the water oxidation catalysis proceeds at the domain edge of NiO₆ octahedra. The XAFS technique provides the first successful direct probing of the active species in the Ni–B_i electrocatalyst during electrochemical reaction

CO Adsorption on Pd–Au Alloy Surface: Reversible Adsorption Site Switching Induced by High-Pressure CO

The interaction between carbon monoxide (CO) and a Pd₇₀Au₃₀(111) alloy surface was investigated under CO pressures with a wide range from ultrahigh vacuum (UHV) to sub-Torr at room temperature by a combination of near-ambient pressure (NAP) X-ray photoelectron spectroscopy and density functional theory calculations. The adsorption site and surface coverage of CO are reversibly controlled by the CO pressure. Under UHV conditions, the CO molecules occupy bridge and hollow sites on contiguous Pd clusters in the Au-rich surface layer. Exposure to sub-Torr CO gas induces site switching of the adsorbed CO on the contiguous Pd clusters from multiple-coordination (hollow and bridge) sites to single-coordination (top) sites, even though the latter sites are energetically less favorable. This behavior is explained by a pressure-induced entropic effect on gas-phase CO, which is in equilibrium with the adsorbed CO. This site switching highlights an important aspect of high-pressure-induced adsorption behavior

Metabolism of Skin-Absorbed Resveratrol into Its Glucuronized Form in Mouse Skin

<div><p>Resveratrol (RESV) is a plant polyphenol, which is thought to have beneficial metabolic effects in laboratory animals as well as in humans. Following oral administration, RESV is immediately catabolized, resulting in low bioavailability. This study compared RESV metabolites and their tissue distribution after oral uptake and skin absorption. Metabolomic analysis of various mouse tissues revealed that RESV can be absorbed and metabolized through skin. We detected sulfated and glucuronidated RESV metabolites, as well as dihydroresveratrol. These metabolites are thought to have lower pharmacological activity than RESV. Similar quantities of most RESV metabolites were observed 4 h after oral or skin administration, except that glucuronidated RESV metabolites were more abundant in skin after topical RESV application than after oral administration. This result is consistent with our finding of glucuronidated RESV metabolites in cultured skin cells. RESV applied to mouse ears significantly suppressed inflammation in the TPA inflammation model. The skin absorption route could be a complementary, potent way to achieve therapeutic effects with RESV.</p></div

Dehydration Pathway for the Dissociation of Gas-Phase Formic Acid on Pt(111) Surface Observed via Ambient-Pressure XPS

While model studies of surface science under ultrahigh vacuum (UHV) have made significant contributions to understanding electrochemistry, many issues related to electrochemical phenomena still remain unanswered due to the extreme environmental differences between UHV and liquid conditions. Electrochemical formic acid (HCOOH) oxidation is one such example. While the dehydration step in the indirect oxidation pathway (HCOOH → H₂O + CO_ad → 2H⁺ + 2e^– + CO₂) is observed in the electrochemical oxidation of formic acid on Pt(111) surface, the surface science studies conducted in UHV condition reported the complete HCOOH dissociation to H₂ and CO₂ on Pt(111) surface with no adsorbed CO at room temperature. A dehydration mechanism may also exist in gas-phase HCOOH dissociation in some conditions different from UHV, but it has not been demonstrated with a surface science method due to pressure limitations. Using ambient pressure X-ray photoelectron spectroscopy (AP-XPS), we observed the dehydration mechanism of gas-phase HCOOH in unprecedented high pressure environment for the first time. This study is a demonstration of reconciling the disagreement between electrocatalysis and surface science by bridging the environment gap

Absorption efficiency of RESV through mouse skin using 3 bases in different tissues.

<p>One mg of RESV dissolved in ethanol was applied directly (EtOH) or mixed with hydrophilic ointment (HO), macrogol (Ma) or CMC gel (CMC), and swabbed on mouse dorsal skin. After 4 h mice were sacrificed, metabolites were extracted from tissues and analyzed by LC-MS. Peak areas of RESV-SULF (<b>A</b>), trans-RESV-3-O-GLUC (<b>B</b>), cis-RESV-3-O-GLUC (<b>C</b>), DH-RESV-SULF (<b>D</b>), DH-RESV-GLUC (<b>E</b>) and tryptophan (<b>F</b>) were normalized using peak areas of spiked internal standards (HEPES and PIPES). Peak areas for each compound are presented as means ± SD of 3 mice. Statistical significance was assessed with Tukey’s test: *P<0.05.</p

Detected RESV and DH-RESV metabolites were identified using standard compounds (STD), MS/MS spectrum analysis (MS/MS), or <i>m/z</i> value (MS).

<p>Detected RESV and DH-RESV metabolites were identified using standard compounds (STD), MS/MS spectrum analysis (MS/MS), or <i>m/z</i> value (MS).</p

RESV metabolism in HepG2 (human hepatocytes), HaCaT (human keratinocytes), and C2C12 (mouse myoblasts).

<p>Cells were treated with 20 or 200 µM RESV for 4 h. After washing with PBS, cells were lysed, and metabolites were extracted and analyzed by LC-MS. Peak areas of RESV–SULF (<b>A</b>), trans-RESV-3-O-GLUC (<b>B</b>) and cis-RESV-3-O-GLUC (<b>C</b>) were normalized by peak areas of spiked internal standards (HEPES and PIPES). Peak areas for each compound are presented as means ± SD of 3 samples (except for HaCaT 200 µM RESV, 2 samples). Statistical significance was assessed using Dunnett’s test: *P<0.05.</p

High-Pressure NO-Induced Mixed Phase on Rh(111): Chemically Driven Replacement

The interaction between nitric oxide (NO) and Rh(111) surface has been investigated by a combination of near-ambient-pressure X-ray photoelectron spectroscopy, low energy electron diffraction, and density functional theory calculations. Under low-temperature and ultrahigh vacuum conditions, our experimental and computational results are consistent with the previous reports for NO adsorption phases on Rh(111). While at room temperature and upon exposure to gaseous NO of 100 mTorr, NO molecules partially dissociate followed by chemical removal of atomic nitrogen by NO from the surface, and the remaining atomic oxygen and NO form a NO/O mixed phase. Interestingly, this mixed phase is stable even after NO evacuation and shows a well-ordered (2 × 2) periodicity. These observations provide a new insight into the NO/Rh(111) system under near-ambient-pressure condition

Integration of Active Nickel Oxide Clusters by Amino Acids for Water Oxidation

The move toward sustainable hydrogen production from water using renewable energy, a highly efficient oxygen evolution electrocatalyst, is crucial because water-splitting efficiency is restricted to the oxygen evolution capability, which is insufficient compared to the hydrogen evolution reaction. Herein, we report a new method that improves the oxygen evolution activity by integration of active nickel oxide clusters using amino acids, meaning that the amount of electrodeposited nickel oxides is increasing with maintaining the catalytic activity. This method enhances the catalytic activity because the reaction sites drastically increase in three dimensions. The detailed reaction mechanism was investigated using operando UV/vis absorption and Ni K-edge X-ray absorption spectroscopic techniques, which suggested that amino acids such as glycine, alanine, and glutamine promoted the electrodeposition of NiO₆ octahedral structure clusters. Meanwhile, the analysis of N and O K-edge X-ray absorption spectra showed that the amino acid (glycine) in the nickel electrocatalyst was present in the molecular state. Therefore, it was spectroscopically demonstrated that amino acids are bound to nickel oxide clusters accompanied by oxygen evolution activity

Operando Observation of NO Reduction by CO on Ir(111) Surface Using NAP-XPS and Mass Spectrometry: Dominant Reaction Pathway to N₂ Formation under Near Realistic Conditions

The nitric oxide (NO) reduction by carbon monoxide (CO) on Ir(111) surfaces under near ambient pressure conditions was studied by a combination of near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) and mass spectrometry (MS), particularly paying attention to the dominant reaction pathway to formation of molecular nitrogen (N₂). Under a relatively low CO pressure condition (50 mTorr NO + 10 mTorr CO), two reaction pathways to form N₂ are clearly observed at different ignition temperatures (280 and 400 °C) and attributed to a reaction of NO adsorbed at atop site (NO_atop) with atomic nitrogen (N_ad) and associative desorption of N_ad, respectively. Since the adsorption of NO_atop is inhibited by CO adsorbed at atop site (CO_atop), the ignition of the NO_atop + N_ad reaction strongly depends on the coverage of CO_atop; the ignition temperature shifts to higher temperature as increasing CO pressure. In contrast, for the N_ad + N_ad reaction the ignition temperature keeps almost constant (∼400 °C). The online MS results indicate that the latter reaction is the dominant pathway to N₂ formation and the former one less contributes to N₂ formation with accompanying a small amount of nitrous oxide (N₂O). No evidence for contribution of the isocyanate (NCO) species as an intermediate was observed in the operando NAP-XP spectra