Probing the Mechanism of Plasmon-Enhanced Ammonia Borane Methanolysis on a CuAg Alloy at a Single-Particle Level

Plasmon-enhanced ammonia borane (AB) methanolysis, as an efficient, controllable, and safe method for hydrogen release, has attracted increasing attention. However, the mechanism remains controversial since it is difficult to directly observe the interface interaction in the plasmonic field. Here, CuAg alloy nanoparticles (NPs) with controlled compositions are synthesized and exhibit an excellent H2 yield (17.1 μmol min–1) under light illumination. Theories and experiments show that both hot carriers and photoinduced local-field enhancement contribute to the improved catalytic activity under light irradiation. More impressively, plasmon-induced interfacial charge transfer between single CuAg NPs and reactant molecules was explored in situ by a single-particle confocal microscope system, and a complete photoluminescence (PL) quenching phenomenon of CuAg NPs was observed when immersed in a methanol solution, not ammonia borane. The PL quenching indicates the transfer of hot electrons to methanol, which is the rate-limiting step of the AB dehydrogenation reaction. In contrast, charge transfer from the plasmonic NP to AB (the most widely proposed path to date) does not work here. This work provides direct evidence for the hot electron transfer from CuAg to methanol via single-particle PL measurement and provides insights for plasmon-enhanced AB methanolysis

Oxygen Vacancy Induced Band-Gap Narrowing and Enhanced Visible Light Photocatalytic Activity of ZnO

Oxygen vacancies in crystal have important impacts on the electronic properties of ZnO. With ZnO₂ as precursors, we introduce a high concentration of oxygen vacancies into ZnO successfully. The obtained ZnO exhibits a yellow color, and the absorption edge shifts to longer wavelength. Raman and XPS spectra reveal that the concentration of oxygen vacancies in the ZnO decreased when the samples are annealed at higher temperature in air. It is consistent with the theory calculation. The increasing of oxygen vacancies results in a narrowing bandgap and increases the visible light absorption of the ZnO. The narrowing bandgap can be confirmed by the enhancement of the photocurrent response when the ZnO was irradiated with visible light. The ZnO with oxygen vacancies are found to be efficient for photodecomposition of 2,4-dichlorophenol under visible light irradiation

High stretching tuned GO decorated non-shrinkable polyacrylic acid-based composite fiber and its excellent performance as a Fenton catalyst

Mixed valent iron ions were used to create a flexible ionic crosslinking network through coordination, making PAA fiber highly stretchable, and the fiber was highly stretched to tear graphene oxide (GO) sheets into discontinuously-dispersed monolayer sheets. The monolayer sheets could construct many hydrogen bonds with PAA chains to serve as knots to hinder chain movement, controlling the shrinkage of stretched fiber. Co-solvent formamide could improve the heat resistance of PAA fiber through special calorific effect; thus the highly-stretched fiber could tolerate high temperature heat setting. Due to the advanced structure induced by stretching, internal force relaxation caused by heat setting, and the existence of knots, the resulting fiber possessed the features of high strength and no shrinkage. High strength made the fiber mechanically applicable, and the unshrinkability could help it to maintain large specific surface area and strong iron ions-immobilizing capability. As a result, the catalytic activity of non-shrinkable fiber was increased by 25% compared with that of shrinkable fiber for methylene blue (MB) decolorization, and iron ion loading ratio was increased by 174.5%; however, iron ion leaching ratio was decreased by 76.5%, which was conducive to reusability improvement. Thereby, the resulting fiber could be repeatedly used to decolorize MB.</p

Chemical Adsorption Enhanced CO₂ Capture and Photoreduction over a Copper Porphyrin Based Metal Organic Framework

Effective CO₂ capture and activation is a prerequisite step for highly efficient CO₂ reduction. In this study, we reported a case of Cu²⁺ in a porphyrin based MOF promoted enhanced photocatalytic CO₂ conversion to methanol. Compared with the sample without Cu²⁺, the methanol evolution rate was improved as high as 7 times. In situ FT-IR results suggested that CO₂ chemical adsorption and activation over Cu²⁺ played an important role in improving the conversion efficiency

Image_1_Six new polyphenolic metabolites isolated from the Suillus granulatus and their cytotoxicity against HepG2 cells.pdf

Edible mushrooms are an important source of nutraceuticals and for the discovery of bioactive metabolites as pharmaceuticals. In this work, six new polyphenolic metabolites suillusol A-D (1–4), suillusinoic acid (5), ethyl suillusinoate (6), were isolated from the Suillus granulatus. The structures of new compounds were elucidated using high-resolution electrospray ionization mass spectroscopy, nuclear magnetic resonance data, and single-crystal X-ray diffraction analysis. As far as we know, compound 1 represents an unprecedented type of natural product and compound 3 represents a new type of polyphenol fungal pigment, which may be biosynthetically related to thelephoric acid. The cytotoxicity against HepG2 cells of the new compounds were also evaluated. Compound 2 demonstrate significant inhibitory activity against HepG2 cells with IC50 values of 10.85 μM, surpassing that of positive control cisplatin. Moreover, compound 1 and 3 also exhibited moderate cytotoxic activity with their IC50 values measured at 35.60 and 32.62 μM, respectively. Our results indicate that S. granulatus is a rich source of chemical constituents that may provide new lead compounds for the development of anticancer agents.</p

Anisotropic Photoelectrochemical (PEC) Performances of ZnO Single-Crystalline Photoanode: Effect of Internal Electrostatic Fields on the Separation of Photogenerated Charge Carriers during PEC Water Splitting

This work investigates the anisotropic PEC performances of ZnO single-crystalline (SC) photoanodes and the effect of internal electrostatic fields on the separation of photogenerated charge carriers during PEC water splitting. It was found that the internal electrostatic field can greatly influence the bulk charge separation efficiencies during PEC water splitting depending on its orientations, which can only be promoted as the internal electrostatic field in accordance with the direction of the holes’ transportation. Due to the surface stabilization of ZnO polar surfaces, the internal electrostatic field would be gradually decreased to zero near the surface of ZnO SC photoanodes. Therefore, the interfacial charge separation would be mainly determined by the interfacial electric fields in the space charge region formed by the equilibration of the Fermi levels between ZnO and the electrolyte solution. However, the differences on the bulk charge separation efficiencies of ZnO SC photoanodes are much larger than that at the interface, which indicated the bulk charge separation could play a more important role on determining the overall charge separation during PEC water splitting. Therefore, the anisotropic PEC performances of ZnO SC photoanodes during PEC water splitting could be mainly attributed to the internal electrostatic fields. With the assistance of the internal electrostatic field, O-SCs yield a record high solar to hydrogen conversion efficiency of 0.78% at 0.7 V vs RHE and a maximum photocurrent density of 1.84 mA cm^–2 at 1.23 V vs RHE with η_b and η_i of 91.6 and 99.5%, respectively. The results demonstrate the effectiveness of internal electrostatic fields in polar single crystals on promoting the bulk charge separation during PEC water splitting, and indicate that polar single crystals could be good candidates to fabricate high efficient PEC photoanodes with high conversion efficiencies

Promoting Photocatalytic CO₂ Methanation by the Construction of Cooperative Copper Dual-Active Sites

Selective photocatalytic CO2 methanation provides an attractive avenue to address energy and environmental issues. However, impediments such as the sluggish adsorption and activation of CO2 and H2O molecules, along with unexpected intermediate desorption, greatly restrict the activity and selectivity of photocatalytic CO2 methanation. To address these issues, we devised a dual-active site catalyst comprising Cu single atoms (SAs) and nanoclusters (NCs) supported on defective TiO2 (Cu1+NCs/BT). As a result, a remarkable CH4 selectivity of 98% with a yield of 19.63 μmol gcat.–1 h–1 can be obtained over the as-prepared Cu1+NCs/BT in pure water. Mechanistic studies reveal the enhanced performance could be ascribed to the synergistic effect of the Cu dual-active sites, where Cu SAs adsorb and activate CO2, while Cu NCs boost H2O adsorption and dissociation for *H coverage. Additionally, the adjacent Cu dual-active site could jointly stabilize the *CO intermediate and reduce the energy barrier for *CO protonation, promoting the multielectron transfer process

Artificial Second-Order Nonlinear Optics in a Centrosymmetric Optical Material BiVO₄: Breaking the Prerequisite for Nonlinear Optical Materials

Second-order nonlinear optics (NLO) is the foundation of frequency conversion for the generation of coherent light at frequencies where lasers have no emissions or operate poorly. The prerequisite for NLO materials is noncentrosymmetric symmetry that can generate an effectively non-counterbalanced spontaneous electronic polarization. Here, we propose that this material restriction can be broadened by controlling the electron distribution with a local internal electrostatic field (IEF), and we demonstrate artificially created and manipulated second harmonic generation (SHG) in a centrosymmetric optical material, a superimposed Co2+- and Mo6+-doped BiVO4 thin film with 2/m point group symmetry, where a homojunction producing tunable effective polarization is formed. The SHG was characterized and tuned by IEF. This work breaks the structural symmetry constraint on NLO materials. Besides, the phase-matching-like condition was realized for the further improvement of the efficient frequency conversion. Because polarization is also a prerequisite for many other functions besides SHG, we believe that this work should provide some inspiration for the further development of optoelectronic, photonic, and electronic materials

Targeted Regulation of the Electronic States of Nickel Toward the Efficient Electrosynthesis of Benzonitrile and Hydrogen Production

Highly efficient electro-oxidation of benzylamine to generate value-added chemicals coupled with the hydrogen evolution reaction (HER) is crucial but challenging. Herein, targeted regulation of the electronic states of Ni sites was realized via simple yet precise nitridation engineering. Benefiting from the insertion of N atoms into the Ni lattice, the Ni3N electrode exhibits superior activity, selectivity, and stability for the benzylamine oxidation reaction (BOR). Especially, under the industrially relevant current (∼250 mA), the Ni3N catalyst remains ∼95% selective for benzonitrile production, reaching 1.43 mmol h–1 cm–2. Experimental and theoretical findings reveal that the formation of Ni–N bonds upshifts the Ni d-band center and optimizes the electrophilic properties of Ni sites, which contributes to the adsorption and dehydrogenations process of benzylamine. Furthermore, due to the work function difference between Ni and Ni3N, a strong mutual interaction occurs at the heterogeneous interface for Ni-Ni3N, which endows it with the appropriate H* adsorption energy and thus excellent HER performance. Impressively, the integrated solar-energy-driven BOR coupled with the HER electrolyzer affords 10 mA cm–2 at an ultralow voltage of 1.4 V and exhibits a promising practical application (ηsolar‑to‑hydrogen = 13.8%). This work offers a new perspective for the bifunctional design of nitrides in the field of electrosynthesis