In this work, we developed a general two-step method to prepare molybdenum carbide (Mo2C) nanoparticles stabilized by a carbon layer on reduced graphene oxide (RGO) sheets. The Mo2C-RGO hybrid showed excellent performance, which is attributed to the intimate interactions between Mo2C and graphene as well as the outer protection of the carbon layer.

Modifications of local structure at atomic level could precisely and effectively tune the capacity of materials, enabling enhancement in the catalytic activity. Here we modulate the local atomic structure of a classical but inert transition metal oxide, tungsten trioxide, to be an efficient electrocatalyst for hydrogen evolution in acidic water, which has shown promise as an alternative to platinum. Structural analyses and theoretical calculations together indicate that the origin of the enhanced activity could be attributed to the tailored electronic structure by means of the local atomic structure modulations. We anticipate that suitable structure modulations might be applied on other transition metal oxides to meet the optimal thermodynamic and kinetic requirements, which may pave the way to unlock the potential of other promising candidates as cost-effective electrocatalysts for hydrogen evolution in industry.

A Mn3O4/Ni foam electrode prepared by a facile method exhibits excellent electrocatalytic performance for the oxygen evolution reaction.

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Phthalocyanines are frequently used as probing molecules in the field of single-molecule surface-enhanced Raman spectroscopy (SERS) and tip-enhanced Raman spectroscopy (TERS). In this work, we systematically compare the SERS and TERS spectra from a thin cobalt phthalocyanine (CoPc) film that is deposited on a Au film. The contributions from electromagnetic (EM), resonance, and charge-transfer enhancements are discussed. Radially and azimuthally polarized vector beams are used to investigate the influences of molecular orientation and the localized surface plasmon resonance (SPR). Furthermore, two different excitation wavelengths (636 and 532 nm) are used to study the resonant excitation effect as well as the involvement of the charge-transfer processes between CoPc and the Au substrate. It is shown that the Raman peaks of CoPc are mostly enhanced by 636 nm excitation through a combination of resonant excitation, high EM enhancement, and chemical enhancement via charge transfer from the metal to the molecule. At 532 nm excitation, however, the SERS and TERS spectra are dominated by photoluminescence, which originates from a photo-induced charge-transfer process from the optically excited molecule to the metal. The contributions of the different enhancement mechanisms explain the optical contrasts seen in the TERS images of Au nanodisks covered by the CoPc film. The insight achieved in this work will help to understand the optical contrast in sub- or single-molecule TERS imaging and apply SERS or TERS in the field of photocatalysis.

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A series of organic nonlinear optical chromophores containing different auxiliary electron-donating groups (alkoxy, benzyloxy and alkyl) and p-conjugated bridges (vinyl and azobenzene) have been synthesized and systematically characterized using UV-Vis spectroscopy, density functional theory calculation and thermogravimetric analysis. The microscopic molecular hyperpolarizability was obtained via the simple solvatochromism method, where the synthesized chromophores were dissolved in several solvents with different refractive index for absorption spectra measurement. It was found that the introduction of auxiliary groups obviously improved the microscopic molecular hyperpolarizability of all the synthesized chromophores, especially for the benzyloxy modified azobenzene based chromophore, up to sevenfold enhancement of molecular hyperpolarizability as well as good visible light transmittance and thermal stability up to 247°C were obtained, which should be mainly attributed to the enhanced charge transfer enabled by the benzyloxy modification that is confirmed by the electron density distribution in the highest occupied molecular orbital and lowest unoccupied molecular orbital.