Rationally Designed Ag@polymer@2-D LDH Nanoflakes for Bifunctional Efficient Electrochemical Sensing of 4-Nitrophenol and Water Oxidation Reaction.

The rational design and demonstration of a facile sequential template-mediated strategy to construct noble-metal-free efficient bifunctional electrocatalysts for efficient oxygen evolution reaction (OER) and electrocatalytic detection of hazardous environmental 4-nitrophenol (4-NP) have continued as a major challenging task. Herein, we construct a novel Ag@polymer/NiAl LDH (designated as APL) nanohybrid as an efficient bifunctional electrocatalyst by a simple hydrolysis method. The well-fabricated APL/GCE exhibited an extensive linear range from 0.1 to 100 µM in optimized conditions. It showed a detection limit (LOD) of 0.0096 µM (9.6 nM) (S/N = 3) for 4-NP in pH 6 by differential pulse voltammetry (DPV). Meanwhile, the newly fabricated APL exhibited outstanding OER activity with a very low overpotential of 259 mV to deliver 10 mA cm-2 current density (J) at a scan rate of 5 mV/s. The Tafel plot value of APL is low (97 mV/dec) compared to that of the benchmark RuO2 due to a fast kinetic reaction. Besides, the durability of the electrocatalyst was assessed by a chronoamperometry test (CA) for 36 h at 1.55 mV vs RHE, and the long-term cycling stability was analyzed by using cyclic voltammetry (CV); after 5000 cycles, the electrocatalyst was highly stable. These demonstrated results could lead to an alternative electrocatalyst construction for the bifunctionally efficient electrochemical sensing of 4-nitrophenol and oxygen evolution reaction.

Template free-synthesis of cobalt-iron chalcogenides [Co0.8Fe0.2L2, L = S, Se] and their robust bifunctional electrocatalysis for the water splitting reaction and Cr(vi) reduction.

The ease of production of materials and showing multiple applications are appealing in this modern era of advanced technology. This paper reports the synthesis of a pair of novel cobalt-iron chalcogenides [Co0.8Fe0.2S2 and Co0.8Fe0.2Se2] with enhanced electro catalytic activities. These ternary metal chalcogenides were synthesized by a one-step template-free approach via a hexamethyldisilazane (HMDS)-assisted synthetic method. Transient photocurrent (TPC) studies and electrochemical impedance spectra (EIS) of these materials showed free electron mobility. Their bifunctional activities were verified in both the electrochemical oxygen evolution reaction (OER) and in the electrochemical reduction of toxic inorganic heavy metal ions [Cr(vi)] in polluted water. The materials showed robust catalytic ability in the oxygen evolution reaction with minimum possible over potential (345 and 350 mV @ η10) as determined by linear sweep voltammetry and the lower Tafel values (52.4 and 84.5 mV dec-1) for Co0.8Fe0.2Se2 and Co0.8Fe0.2S2 respectively. Surprisingly, both the materials also showed an excellent activity towards electrochemical Cr(vi) reduction to Cr(iii). Besides the maximum current achieved for Co0.8Fe0.2S2, a minimum value for the Limit of detection (LOD) was obtained for Co0.8Fe0.2S2 (0.159 µg L-1) compared to Co0.8Fe0.2Se2 (0.196 µg L-1). We tested the durability of catalysts, the critical factor for the prolonged use of catalysts, through the recyclability measurements of these materials as catalysts. Both the catalysts presented outstanding durability and balanced electro catalytic activities for up to 1500 CV cycles, and chronoamperometry studies also confirmed exceptional stability. The enhanced catalytic activities of these materials are ascribed to the free electron movement, evidenced by the increased TPC measured and EIS. Therefore, the template-free synthesis of these electro catalysts containing non-noble metal illustrates the practical approach to develop such types of catalysts for multiple functions.

Three-dimensional porous MoS2 nanobox embedded g-C3N4@TiO2 architecture for highly efficient photocatalytic degradation of organic pollutant.

Herein, a simple, highly efficient and stable MoS2 nanobox embedded graphitic-C3N4@TiO2 (g-CN@TiO2) nanoarchitecture was synthesized by a facile solvothermal approach. The nano-hybrid photocatalyst was constructed by TiO2 nanoparticles anchored on the surface of g-CN nanosheets. Then highly crystalline three-dimensional porous MoS2 nanobox was homogeneously distributed on the g-CN@TiO2 surface. The g-CN@TiO2/MoS2 hybrid achieved a high photocatalytic degradation efficiency of 97.5% for methylene blue (MB) dye pollutant under visible-light irradiant in an hour which was much better than TiO2@MoS2, g-CN@TiO2, MoS2, TiO2 and g-CN. Furthermore, the reaction rate (k) value of g-CN@TiO2/MoS2 for MB dye is as high as 3.18 X 10-2 min-1, which is ~ 2.65 times better than those of g-CN@TiO2 and MoS2. This work presents a rational structure design, interfacial construction and suitable band gap strategy to synthesize advanced nano-hybrid photocatalyst for degradation of organic pollutant with excellent performance and long-term stability.

A three-dimensional porous CoSnS@CNT nanoarchitecture as a highly efficient bifunctional catalyst for boosted OER performance and photocatalytic degradation.

It is urgent and significant to develop competent, inexpensive transition metal-based catalysts with multifunctional catalytic properties for wide applications. To meet this requirement, herein, for the first time, we present a novel bifunctional CoSnS@CNT hybrid via a simple one-pot surfactant-free hydrothermal method. The CoSnS@CNT hybrid has a unique three-dimensional (3D) porous nanoarchitecture, which is constructed by ultrathin CoSnS homogenously and compactly anchored on a highly conductive CNT skeleton. The porous nanoarchitecture of CoSnS@CNT provides abundant catalytic sites and facilitates ion diffusion, and the CNT skeleton accelerates electron transfer. Benefitting from these merits, the CoSnS@CNT hybrid acted as a bifunctional catalyst with boosted electrocatalytic and photocatalytic performance, where it delivered a tremendous oxygen evolution reaction (OER) performance with a low overpotential of 330 mV at a current density of 10 mA cm-2 and excellent outstanding stability. Moreover, it showed 91.72% photocatalytic degradation for Rhodamine B dye, which is 2-times higher than that of bare CoSnS. This study presents a systematic approach to judiciously design nanostructures and simply synthesize non-noble metal-based bifunctional catalysts with boosted electrocatalytic and photocatalytic activities.

W2C nanodot-decorated CNT networks as a highly efficient and stable electrocatalyst for hydrogen evolution in acidic and alkaline media.

Although tungsten carbide (W2C) has long been reported as an excellent platinum-like catalyst, it is still a challenge to synthesize W2C as an electrocatalyst for a highly efficient hydrogen evolution reaction (HER) due to its high onset overpotential, inevitable aggregation, and lack of a scalable and controllable synthesis method. Herein, we synthesized W2C nanodot-decorated CNT networks (W2C@CNT-S) via a facile and scalable spray drying method followed by a carbonization process. It is demonstrated that this unique nanoarchitecture, constructed by ultrafine W2C nanodots homogeneously decorated on a three-dimensional and conductive CNT skeleton, leads to the exposure of abundant catalytic sites and promotes highly efficient electron transfer and ion diffusion during the HER process. As a result, in acidic and alkaline media, the optimized W2C@CNT-S hybrid exhibited excellent HER performance with very low onset overpotentials of only 60 and 40 mV (vs. RHE) and very small Tafel slopes of 57.4 and 56.2 mV dec-1, and only needed 176 and 148 mV (vs. RHE) to obtain a current density of 10 mA cm-2, respectively; it also showed outstanding long-term durability even after a 30-hour test in both acidic and alkaline media. This study presents an overview of a low-cost and scalable spray-drying strategy to synthesize a high-performance carbide-based electrocatalyst for hydrogen evolution.

Ag@Ag8W4O16 nanoroasted rice beads with photocatalytic, antibacterial and anticancer activity.

Increasing resistance of pathogens and cancer cell line towards antibiotics and anticancer agents has caused serious health problems in the past decades. Due to these problems in recent years, researchers have tried to combine nanotechnology with material science to have intrinsic antimicrobial and anticancer activity. The metals and metal oxides were investigated with respect to their antimicrobial and anticancer effects towards bacteria and cancer cell line. In the present work metal@metal tungstate (Ag@Ag8W4O16 nanoroasted rice beads) is investigated for antibacterial activity against Escherichia coli and Staphylococcus aureus using Mueller-Hinton broth and the anticancer activity against B16F10 cell line was studied. Silver decorated silver tungstate (Ag@Ag8W4O16) was synthesized by the microwave irradiation method using Cetyl Trimethyl Ammonium Bromide (CTAB). Ag@Ag8W4O16 was characterized by using various spectroscopic techniques. The phase and crystalline nature were analyzed by using XRD. The morphological analysis was carried out using Field Emission Scanning Electron Microscopy (FE-SEM), and High Resolution Transmission Electron Microscopy (HR-TEM). Further, Fourier Transform Infrared Spectroscopy (FT-IR) and Raman spectral analysis were carried out in order to ascertain the presence of functional groups in Ag@Ag8W4O16. The optical property was investigated using Diffuse Reflectance Ultraviolet-Visible Spectroscopy (DRS-UV-Vis) and the band gap was found to be 3.08eV. Surface area of the synthesized Ag@Ag8W4O16 wasanalyzed by BET analysis and Ag@Ag8W4O16 was utilized for the degradation of organic dyes methylene blue and rhodamine B. The morphology of the Ag@Ag8W4O16 resembles roasted rice beads with breath and length in nm range. The oxidation state of tungsten (W) and silver (Ag) was investigated using X-ray photoelectron spectroscopy (XPS).