Changqing Li

Amorphous MoSx developed on Co(OH)2 nanosheets generating efficient oxygen evolution catalysts

Exploration of high-efficiency and inexpensive electrocatalysts for the oxygen evolution reaction (OER) is of great importance for the design of renewable energy storage and conversion devices. Herein, we prepared amorphous MoSx-encapsulated Co(OH)2 nanosheets (aMoSx/Co(OH)2 NSs) as strongly robust and active OER electrocatalysts via a three-step procedure: first, Co(OH)2 nanosheets with catalytically active octahedral MO6 structures were synthesized by the hydrothermal process; second, violent ultrasonication was applied to exfoliate individual nanosheets from stacked Co(OH)2 sheets and break them down into smaller sheets and attach MoS42− ions uniformly on the nanosheets; third, MoS42− ions were thermally decomposed into amorphous MoSx on the Co(OH)2 nanosheets. The role of the incorporation of the amorphous MoSx nanostructure was to enhance the surface hydrophilicity for the availability of H2O and accelerate the electron transport capability for kinetic activities. Furthermore, the interaction between MoSx and Co(OH)2 is proposed to induce electron transfer from amorphous MoSx to Co(OH)2, which will promote the basic environment for cobalt sites, break the Co–O bond, favor the release of O2 molecules, and thus enhance the OER process. Optimization of the Co/Mo molar ratio demonstrated that aMoSx/Co(OH)2 NSs with the Co/Mo molar ratio of 8 had the best OER activity and delivered the overpotential of 350 mV at the current density of 10 mA cm−2 and the Tafel slope of 65.4 mV dec−1 in 0.1 M KOH. This study enriches the research on non-first-row (3d) metal incorporation for high-efficient OER catalysts and offers an alternative to noble metal catalysts.

One-Step Pyrolysis Transformation of Mulberry Leaves Followed by Electrochemical Treatment: Preparing of M (M = Pt, Au) Nanoparticles Incorporated Nitrogen-Doped Carbon Nanoporous Structures as Efficient Electrocatalyst for Hydrogen Evolution Reaction

To facilely develop low-cost and efficient hydrogen evolution electrocatalysts, catalyst with low content of platinum on nitrogen-doped carbon nanoporous structures were prepared for hydrogen evolution reaction (HER). This study firstly demonstrated the one-step pyrolysis transformation of conveniently accessible mulberry leaves to obtain nitrogen-doped nanoporous carbons (N-NPCs) for hydrogen evolution reaction. After electrochemical treatment, the obtained N-NPCs-ET with Pt as counter electrode exhibited an unexpected high hydrogen evolution activity, which had low onset overpotential of 100 mV and a Tafel slope of 60 mV dec-1. N-NPCs-ET maintained catalytic activity for at least 10 h in 0.5 M H2SO4 solution. The enhanced HER performance was relevant to the incorporation of Pt nanoparticles, which were dissolved from anodic Pt counter electrode in acid media and precipitated into cathodic N-NPCs surface again. Moreover, for the first time, we found that with a gold electrode as the counter electrode, Au nanoparticles could be incorporated into N-NPCs by electrochemical treatments and the formed Au nanoparticles decorated N-NPCs possessed efficient catalytic activity toward HER.

Enhanced Visible Light Photocatalytic Decolorization of Methylene Blue by Hierarchical Ternary Nanocomposites Cu–TiO2-Mesoporous-Silica Microsphere

In this study, hierarchical ternary nanocomposites, i.e., Cu-TiO2-mesoporous silica microspheres (Cu-TiO2-MSM), were synthesized as ternary photocatalyst system to improve the visible light photocatalytic degradation of the environmental pollutant model dye methylene blue (MB). The innovation of this method is in situ depositing TiO2 and Cu2O nanoparticles sequentially onto the surface of mesoporous silica microspheres to form highly active heterostructure. The improved activity for the degradation of MB is attributed to: (1) the high adsorption capacity of the porous and interconnected-channel-structure MSM to MB; (2) the valence band electrons of TiO2 released from the conduction band generating abundant highly active free radicals, which directly reacted with adsorbed MB. The photocatalytic degradation efficiency to MB was found to be 98% in 5 min, and almost 100% in 20 min. This study paves a way for the development of a ternary-doped catalyst for visible light photocatalytic degradation and may exhibit widely application in industry.

Fabrication of a Flexible and Stretchable Nanostructured Gold Electrode Using a Facile Ultraviolet-Irradiation Approach for the Detection of Nitric Oxide Released from Cells

We developed a simple and environmentally friendly ultraviolet (UV)-irradiation-assisted technique to fabricate a stretchable, nanostructured gold film as a flexible electrode for the detection of NO release. The flexible gold film endows the electrode with desirable electrochemical stability against mechanical deformation, including bending to different curvatures and bearing repeated bending circumstances (200 times). The flexible nanostructured gold electrodes can catalyze NO oxidation at 0.85 V (as opposed to Ag/AgCl) and detect NO within a wide linearity in the range of 10 nM to 1.295 μM. Its excellent NO-sensing ability and its stretchability together with its biocompatibility allows the electrode to electrochemically monitor NO release from mechanically sensitive HUVECs in both their unstretched and stretched states. This result paves the way for an effective and easily accessible platform for designing stretchable and flexible electrodes and opens more opportunities for sensing chemical-signal molecules released from cells or other biological samples during mechanical stimulation.