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Cation segregation occurring near the surface or interfaces of solid catalysts plays an important role in catalytic reactions. Unfortunately, the native surface of perovskite oxides is dominated by passivated A-site segregation, which severely hampers the catalytic activity and durability of the system. To address this issue, herein, we present a wet exsolution method to reconstruct surface segregation in perovskite cobalt oxide. Under reduction etching treatment of glycol solution, inert surface Sr segregation was transformed into active Co

Improved activity and stability Pt-based catalysts for the oxygen reduction reaction (ORR) are needed to perpetuate the deployment of polymer electrolyte fuel cells (PEFCs) in the transportation sector. Here, we use atomic layer deposition of TiO2 and Pt coupled with thermal reductive annealing to prepare Pt3Ti electrocatalysts. The atomic level synthetic control resulted in Pt3Ti nanoparticles with high ORR performance, including a mass activity of 1.84 A/mgPt and excellent electrochemical stability. The Pt3Ti nanoparticles show excellent specific activity — 5.3-fold higher than commercial Pt/C and 3-fold higher than polycrystalline Pt, exceeding the performance of any PtTi catalysts reported to date. Combined experimental and computational efforts indicate that Pt enrichment on the Pt3Ti enhances the activity, and the intrinsic stability of the Pt3Ti phase provides durability. This knowledge, along with the facile fabrication of alloys by atomic layer deposition, can be leveraged to designed improved performance catalysts.

Stabilising waterlogged archaeological wooden artefacts for display presents a challenge for conservators and scientists. Sulfur compounds, incorporated into the wood prior to excavation, can lead to acid formation when exposed to oxygen, and in the presence of iron ions. Strontium carbonate nanoparticles have recently been shown to reduce the production of acid formation at the root by reacting with inorganic sulfur-containing compounds. Here, we show the feasibility of using this treatment on small samples where consolidating treatments have already been performed. It is found that PEG 200 does not prevent the reactivity of the nanoparticles with the sulfur compounds present in the artefacts. A surface brushing application method was found to be successful whilst retaining the visual integrity. In addition, it was found that this technique results in the leaching of iron from the surface layers, preventing future build up of acid catalysed by iron compounds.

Wooden archeological artifacts excavated from marine sources contain problematic sulfur which can result in degradation. A treatment to safely neutralize sulfur using alkaline earth carbonates is tested on samples from the warship the Mary Rose. S K-edge X-ray Absorption Spectroscopy confirms the neutralization of acid already in the wood, by forming insoluble sulfate salts. The treatment also catalyzes the conversion of iron sulfides to soluble iron sulfates, thus removing the future source of this acid. Calcium carbonate is favored as it is non-toxic and economical. This treatment is relevant to all organic artifacts that are threatened by sulfur compounds.

Metal K-edge X-ray absorption spectroscopy (XAS) has been extensively applied to bioinorganic chemistry to obtain geometric structure information on metalloprotein and biomimetic model complex active sites by analyzing the higher energy extended X-ray absorption fine structure (EXAFS) region of the spectrum. In recent years, focus has been on developing methodologies to interpret the lower energy K-pre-edge and rising-edge regions (XANES) and using it for electronic structure determination in complex bioinorganic systems. In this review, the evolution and progress of 3d-transition metal K-pre-edge and rising-edge methodology development is presented with particular focus on applications to bioinorganic systems. Applications to biomimetic transition metal–O2 intermediates (M = Fe, Co, Ni and Cu) are reviewed, which demonstrate the power of the method as an electronic structure determination technique and its impact in understanding the role of supporting ligands in tuning the electronic configuration of transition metal–O2 systems.

The preservation of waterlogged archaeological wooden finds, such as Henry VIII's flagship the Mary Rose 1 , 2 , 3 , is complicated by the biological, chemical, and mechanical changes induced from prolonged exposure to a marine environment. Of particular concern are sulfur species that form acidic compounds that attack wood 4 . Here we show that different sulfur compounds do not form acids at the same rate or pathway and propose a preservation strategy of applying SrCO3 nanoparticles. These nanoparticles not only neutralize problematic sulfuric acid, but also reduced sulfur compounds, such as sulfur and pyrite, which pose a long term threat. This is the first treatment that eliminates acidification at the root. Although this strategy was devised for the Mary Rose, it could be employed to preserve any archaeological organic artifact rich in problematic sulfur, from sunken ships 5 , 6 and silk tapestries 7 to ancient texts 8 and parchments 9 .

Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations have been used to elucidate differences in the sulfur K-edge spectra of three pairs of related compounds: methionine and S ( Me ) 3 + , cystine and (±)6-thioctic amide, and (Me)2SO3 and (CH2)2SO3. TD-DFT is shown to accurately reproduce all the experimental XAS spectra. The 2 eV energy difference in the sulfur K-edge rising edge position between methionine and trimethylsulfonium is shown to derive from changes in bonding rather than the increase in effective nuclear charge. A similar insensitivity to effective nuclear charge is found in the XAS spectra of cystine and (±)6-thioctic amide. These surprising results are traced back to the fact that XAS spectra reflect orbital energy differences, rather than a measure of the atomic potential. The change in atomic potential following oxidation or reduction affects the core and valence orbitals almost equally. In all cases DFT calculations showed that the dramatic differences in sulfur K-edge spectra found between functional groups in alternative molecular environments derive from the variations in orbital mixing and energies following from bonding. However, XAS rising-edge energy positions have a near linear correlation with oxidation state. This is attributed to the fact that bond strength typically increases with oxidation state. Therefore, although XAS rising-edge energies are an approximate measure of the oxidation state of the absorbing atom, it is important to recognize that the correlation of XAS edge energy with effective nuclear charge is not direct. This result is finally applied to the question of quantitative sulfur speciation in complex materials of chemical, biological, or geological origin.