The electrochemical N2 reduction reaction (NRR) offers a direct pathway to produce NH3 from renewable energy. However, aqueous NRR suffers from both low Faradaic efficiency (FE) and low yield rate. The main reason is the more favored H+ reduction to H2 in aqueous electrolytes. Here we demonstrate a highly selective Ru/MoS2 NRR catalyst on which the MoS2 polymorphs can be controlled to suppress H+ reduction. A NRR FE as high as 17.6% and NH3 yield rate of 1.14 × 10–10 mol cm–2 s–1 are demonstrated at 50 °C. Theoretical evidence supports a hypothesis that the high NRR activity originates from the synergistic interplay between the Ru clusters as N2 binding sites and nearby isolated S-vacancies on the 2H-MoS2 as centers for hydrogenation; this supports formation of NH3 at the Ru/2H-MoS2 interface.

We report key results of a systematic computational investigation using density functional theory along with the two standard Perdew–Burke–Ernzerhof and hybrid Heyd–Scuseria–Ernzerhof (HSE06) exchange–correlation formalisms on essential fundamental parameters for solar energy conversion of a series of large, medium, and small selected (covalent, binary, and ternary) materials widely utilized in fuel cells, photocatalysis, optoelectronics, photovoltaics, and dye-sensitized solar devices such as BN, AlN, C, ZrO2, Na2Ta4O11, Bi4Ti3O12, ZnS, GaN, SrTiO3, TiO2, Bi12TiO20, SiC, WO3, TaON, ZnSe, BiVO4, CuNbO3, CdS, AlP, ZnTe, GaP, Cu2O, AlAs, Ta3N5, BP, CdSe, SnWO4, GaAs, CdTe, and Si. Our calculations highlight that the optoelectronic and redox parameters computed with HSE06 reproduce with very good accuracy the experimental results, thanks to precise electronic structure calculations. Applying this first-principle quantum methodology led us to provide a rational design of new suitable solid solution materials for visible light-driven photochemical water splitting. This valuable computational tool will be applied to predict promising candidates to be experimentally prepared and tested for solar-to-chemical energy conversion.

A well-defined aluminium-bound hydroxyl group on the surface of mesoporous SBA-15, [(≡Si−O−Si≡) (≡Si−O) Al−OH], 3 was obtained by reacting di-isopropyl aluminium hydride with SBA-15 treated at 700 °C. The resulting surface [(≡Si−O−Si≡) (≡Si−O) Al (isobutyl) fragment undergoes β-H elimination at 400 °C leading to [(≡Si−O−Si≡)(≡Si−O−)Al−O) Al−H]. Further oxidation of this Al-hydride with NO leads to 3. This acidic support was used to create a well-defined surface organo-tungsten fragment [(≡Si−O−Si≡)(≡Si−O−)Al−O−W(≡CtBu)(CHtBu)] by reacting 3 with W(≡C-tBu)(CH-tBu). A further reaction with hydrogen under mild conditions afforded the tungsten carbyne bis-hydride [(≡Si−O−Si≡)(≡Si−O−)Al−O−W(H)(≡C-tBu)]. The performance of each of the W-supported catalysts was assessed for propane metathesis in a flow reactor at 150 °C. [(≡Si−O−Si≡)(≡Si−O−) Al−O−W(≡CtBu)(H)] was found to be a single-site catalyst, giving the highest turnover number (TON=800) and the highest reported selectivity for butane (45 %) vs. ethane (32 %) known for oxide-supported tungsten complex catalysts (with the supports being silica, silica-alumina, and alumina). The results demonstrate that modification of the oxide ligands on silica via the creation of Al Lewis acid center as an anchoring site for organometallic complexes opens up new catalytic properties, markedly enhancing the catalytic performance of supported organo-tungsten species.

Several standard semiempirical methods as well as the MMFF94 force field approximation have been tested in reproducing 8 DLPNO-CCSD(T)/cc-pVTZ level conformational energies and spatial structures for 37 organic molecules representing pharmaceuticals, drugs, catalysts, synthetic precursors, industry-related chemicals (37conf8 database). All contemporary semiempirical methods surpass their standard counterparts resulting in more reliable conformational energies and spatial structures, even though at significantly higher computational costs. However, even these methods show unexpected failures in reproducing energy differences between several conformers of the crown ether 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6). Inexpensive force field MMFF94 approximation groups with contemporary semiempirical methods in reproducing the correct order of conformational energies and spatial structures, although the performance in predicting absolute conformational energies compares to standard semiempirical methods. Based on these findings, we suggest a two-step strategy for reliable yet feasible conformational search and sampling in realistic-size flexible organic molecules: i) geometry optimization/preselection of relevant conformers using the MMFF94 force field; ii) single-point energy evaluations using a contemporary semiempirical method. We expect that developed database 37conf8 is going to be useful for development of semiempirical methods.

The first turnover event of an olefin metathesis reaction using a new family of homogenous Ru-based catalysts bearing modified indenylidene ligands has been investigated, using methoxyethylene as a substrate. The study is carried out by means of density functional theory (DFT). The indenylidene ligands are decorated with ortho-methyl and isopropyl groups at both ortho positions of their phenyl ring. DFT results highlight the more sterically demanding indenylidenes have to undergo a more exothermic first phosphine dissociation step. Overall, the study emphasises advantages of increased steric hindrance in promoting the phosphine release, and the relative stability of the corresponding metallacycle over classical ylidene ligands. Mayer bond orders and steric maps provide structural reasons for these effects, whereas NICS aromaticity and conceptual DFT confirm that the electronic parameters do not play a significant role.

The development of hydrogen bond donors (HBDs) as catalytic moieties in the cycloaddition of carbon dioxide to epoxides is an active field of research to access efficient, inexpensive and sustainable metal-free systems for the conversion of carbon dioxide to useful chemicals. Thus far, no systematic attempt to correlate the activity of a diverse selection of HBDs to their physico-chemical properties has been undertaken. In this work, we investigate factors influencing the catalytic activity of hydroxyl HBDs from different chemical families under ambient conditions by considering the HBDs Brønsted acidity (expressed as pKa), the number of hydroxyls and structural aspects. As an effect, this study highlights the crucial role of the hydroxyl protons’ Brønsted acidity in determining the catalytic activity of the HBDs, identifies an ideal range for the hydroxyl HBDs proton acidity (9 <pKa <11) and leads to a revaluation of phenol and to the discovery of a simple ascorbic acid derivative as efficient HBDs for the title cycloaddition reaction. Density functional theory (DFT) calculations show mild reactions barriers for the reaction catalysed by phenol and suggest the occurrence of aggregation between molecules of ascorbic acid as a further factor affecting catalytic activity.

Recent progress on bismuth vanadate (BiVO) has shown it to be among the highest performing metal oxide photoanode materials. However, further improvement, especially in the form of thin film photoelectrodes, is hampered by its poor charge carrier transport and its relatively wide bandgap. Here, sulfur incorporation is used to address these limitations. A maximum bandgap decrease of ∼0.3 eV is obtained, which increases the theoretical maximum solar-to-hydrogen efficiency from 9 to 12%. Hard X-ray photoelectron spectroscopy measurements as well as density functional theory calculations show that the main reason for the bandgap decrease is an upward shift of the valence band maximum. Time-resolved microwave conductivity measurements reveal a ∼3 times higher charge carrier mobility compared to unmodified BiVO, resulting in a ∼70% increase in the carrier diffusion length. This work demonstrates that sulfur incorporation can be a promising and practical method to improve the performance of wide-bandgap metal oxide photoelectrodes.

Sulfurized polyacrylonitrile (SPAN) is the most promising cathode for next-generation lithium–sulfur (Li–S) batteries due to the much improved stability. However, the molecular structure and reaction mechanism have not yet been fully understood. Herein, we present a new take on the structure and mechanism to interpret the electrochemical behaviors. We find that the thiyl radical is generated after the cleavage of the S–S bond in molecules in the first cycle, and then a conjugative structure can be formed due to electron delocalization of the thiyl radical on the pyridine backbone. The conjugative structure can react with lithium ions through a lithium coupled electron transfer process and form an ion-coordination bond reversibly. This could be the real reason for the superior lithium storage capability, in which the lithium polysulfide may not be formed. This study refreshes current knowledge of SPAN in Li–S batteries. In addition, the structural analysis is applicable to analyze the current organic cathodes in rechargeable batteries and also allows further applications in Al–S batteries to achieve high performance.

A novel method for the synthesis of the homogeneous homoleptic cationic tantalum(V)tetramethyl complex [(TaMe4)+ MeB(C6F5)3−] from neutral tantalumpentamethyl (TaMe5) has been described, by direct demethylation using B(C6F5)3 reagent. The aforesaid higher valent cationic tantalum complex was characterized precisely by liquid state 1H-NMR, 13C-NMR, and 1H-13C-NMR correlation spectroscopy.

Carbon monoxide participates in many copper-catalyzed reactions, which makes CO-induced structural changes of Cu catalysts key for important industrial processes. We have studied the interaction of carbon monoxide with the Cu(100) single crystal termination at 120, 200, and 300 K by means of low energy electron diffraction (LEED), temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), polarization-modulation infrared reflection absorption spectroscopy (PM-IRAS), and density functional theory (DFT) calculations. The absorption band of CO (2082 to 2112 cm-1) at elevated gas pressure (up to 5 mbar) and at 200/300 K was found at higher wavenumber than the characteristic band of the c(2×2)CO structure, and was consistent with CO adsorbed on low-coordinated Cu atoms. The combined PM-IRAS/DFT analysis revealed that exposure to CO induces surface roughening through the formation of Cu adatoms and clusters on the (100) terraces. The roughened surface seemed surprisingly active for CO dissociation, which indicates its unique catalytic properties.