Real-time monitored photocatalytic activity and electrochemical performance of an rGO/Pt nanocomposite synthesized via a green approach

Herein, we have reported the real-time photodegradation of methylene blue (MB), an organic pollutant, in the presence of sunlight at an ambient temperature using a platinum-decorated reduced graphene oxide (rGO/Pt) nanocomposite. The photocatalyst was prepared via a simple, one-pot and green approach with the simultaneous reduction of GO and Pt using aqueous honey as a reducing agent. Moreover, the honey not only simultaneously reduced Pt ions and GO but also played a key role in the growth and dispersion of Pt nanoparticles on the surface of rGO. Various rGO/Pt nanocomposites with different percentages of Pt nanoparticles loaded on rGO were obtained by tuning the concentration of the Pt source. The high percentage of Pt nanoparticles with an average size of 2.5 nm dispersed on rGO has shown excellent electrochemical performance. The photocatalytic activity of the rGO/Pt composite was enhanced by increasing the weight percent of the Pt particles on rGO, which led to the formation of a highly efficient photocatalyst. The optimized photocatalyst exhibited remarkable photocatalytic activity and degraded 98% MB in 180 minutes; thus, it can be used for industrial and environmental applications.

Ultrafine Pt Nanoparticles Stabilized by MoS2/N-Doped Reduced Graphene Oxide as a Durable Electrocatalyst for Alcohol Oxidation and Oxygen Reduction Reactions

Direct alcohol fuel cells play a pivotal role in the synthesis of catalysts because of their low cost, high catalytic activity, and long durability in half-cell reactions, which include anode (alcohol oxidation) and cathode (oxygen reduction) reactions. However, platinum catalysts suffer from CO tolerance, which affects their stability. The present study focuses on ultrafine Pt nanoparticles stabilized by flowerlike MoS₂/N-doped reduced graphene oxide (Pt@MoS₂/NrGO) architecture, developed via a facile and cost-competitive approach that was performed through the hydrothermal method followed by the wet-reflux strategy. Fourier transform infrared spectra, X-ray diffraction patterns, Raman spectra, X-ray photoelectron spectra, field-emission scanning electron microscopy, and transmission electron microscopy verified the conversion to Pt@MoS₂/NrGO. Pt@MoS₂/NrGO was applied as a potential electrocatalyst toward the anode reaction (liquid fuel oxidation) and the cathode reaction (oxygen reduction). In the anode reaction, Pt@MoS₂/NrGO showed superior activity toward electro-oxidation of methanol, ethylene glycol, and glycerol with mass activities of 448.0, 158.0, and 147.0 mA/mg_Pt, respectively, approximately 4.14, 2.82, and 3.34 times that of a commercial Pt-C (20%) catalyst. The durability of the Pt@MoS₂/NrGO catalyst was tested via 500 potential cycles, demonstrating less than 20% of catalytic activity loss for alcohol fuels. In the cathode reaction, oxygen reduction reaction results showed excellent catalytic activity with higher half-wave potential at 0.895 V versus a reversible hydrogen electrode for Pt@MoS₂/NrGO. The durability of the Pt@MoS₂/NrGO catalyst was tested via 30 000 potential cycles and showed only 15 mV reduction in the half-wave potential, whereas the Pt@NrGO and Pt-C catalysts experienced a much greater shift (Pt@NrGO, ∼23 mV; Pt-C, ∼20 mV).

Experimental and density functional theory investigation of Pt-loaded titanium dioxide/molybdenum disulfide nanohybrid for SO2 gas sensing

A high-performance sulfur dioxide sensor based on a platinum-loaded titanium dioxide/molybdenum disulfide ternary nanocomposite is synthesized via layer-by-layer self-assembly.

Recent progress in Pt and Pd-based hybrid nanocatalysts for methanol electrooxidation

Hybrid nanomaterials can combine merits of different components and modulate electronic states of Pt and Pd based nanocrystals simultaneously.

Bimetallic Pt-Pd nanostructures supported on MoS2 as an ultra-high performance electrocatalyst for methanol oxidation and nonenzymatic determination of hydrogen peroxide

The authors report on a composite based electrocatalyst for methanol oxidation and H₂O₂ sensing. The composite consists of Pt nanoparticles (NPs), Pd nanoflakes, and MoS₂. It was synthesized by chemical reduction followed by template-free electro-deposition of Pt NPs. FESEM images of the Pd nanoflakes on the MoS₂ reveal nanorod-like morphology of the Pd NPs on the MoS₂ support, whilst FESEM images of the Pt-Pd/MoS₂ composite show Pt NPs in high density and with the average size of ~15 nm, all homogeneously electrodeposited on the Pd-MoS₂ composite. A glassy carbon electrode (GCE) was modified with the composite to obtain an electrode for methanol oxidation and H₂O₂ detection. The modified GCE exhibits excellent durability with good catalytic efficiency (the ratio of forward and backward peak current density, I_f/I_b, is 3.23) for methanol oxidation in acidic medium. It was also used to sense H₂O₂ at an applied potential of -0.35 V vs. Ag|AgCl which can be detected with a 3.4 μM lower limit of detection. The sensitivity is 7.64 μA μM^-1 cm^-2 and the dynamic range extends from 10 to 80 μM. This enhanced performance can be explained in terms of the presence of higher percentage of metallic 1T phase rather than a semiconducting 2H phase in MoS₂. In addition, this is a result of the high surface area of MoS₂ with interwoven nanosheets, the uniform distribution of the Pt NPs without any agglomeration on MoS₂ support, and the synergistic effect of Pt NPs, Pd nanoflakes and MoS₂ nanosheets. In our perception, this binder-free nano-composite has promising applications in next generation energy conversion and in chemical sensing. Graphical abstract A composite consisting of palladium nanoflakes and molybdenum disulfide was decorated with platinum nanoparticles and then placed on a glassy carbon electrode which is shown to be a viable electrocatalyst for both methanol oxidation and detection of hydrogen peroxide.

Pt decorated MoS2 nanoflakes for ultrasensitive resistive humidity sensor

In this work, we report the fabrication of a low power, humidity sensor where platinum nanoparticles (NPs) decorated few-layered molybdenum disulphide (MoS2) nanoflakes have been used as the sensing layer. A mixed solvent was used to exfoliate the nanoflakes from the bulk powder. Then the Pt/MoS2 composites were prepared by reducing Pt NPs from chloroplatinic acid hexahydrate using a novel reduction technique using sulphide salt. The successful reduction and composite preparation were confirmed using various material characterization tools like scanning electron microscopy, atomic force microscopy, transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, Raman spectroscopy and UV-visible spectroscopy. The humidity sensors were prepared by drop-coating the Pt-decorated MoS2 on gold interdigitated electrodes and then exposed to various levels of relative humidity (RH). Composites with different weight ratios of Pt were tested and the best response was shown by the Pt/MoS2 (0.25:1) sample with a record high response of ∼4000 times at 85% RH. The response and recovery times were ∼92 s and ∼154 s respectively with repeatable behaviour. The sensor performance was found to be stable when tested over a few months. The underlying sensing mechanisms along with detailed characterization of the various composites have been discussed.

Nanoscale PtO2 Catalysts-Loaded SnO2 Multichannel Nanofibers toward Highly Sensitive Acetone Sensor

PtO₂ nanocatalysts-loaded SnO₂ multichannel nanofibers (PtO₂-SnO₂ MCNFs) were synthesized by single-spinneret electrospinning combined with apoferritin and two immiscible polymers, i.e., poly(vinylpyrrolidone) and polyacrylonitrile. The apoferritin, which can encapsulate nanoparticles within a small inner cavity (8 nm), was used as a catalyst loading template for an effective functionalization of the PtO₂ catalysts. Taking advantage of the multichannel structure with a high porosity, effective activation of catalysts on both interior and exterior site of MCNFs was realized. As a result, under high humidity condition (95% RH), PtO₂-SnO₂ MCNFs exhibited a remarkably high acetone response (R_air/R_gas = 194.15) toward 5 ppm acetone gases, superior selectivity to acetone molecules among various interfering gas species, and excellent stability during 30 cycles of response and recovery toward 1 ppm acetone gases. In this work, we first demonstrate the high suitability of multichannel semiconducting metal oxides structure functionalized by apoferritin-encapsulated catalytic nanoparticles as highly sensitive and selective gas-sensing layer.

Fast preparation of MoS2 nanoflowers decorated with platinum nanoparticles for electrochemical detection of hydrogen peroxide

MoS₂ nanoflowers decorated with Pt nanoparticles show enhanced performances for electrochemical H₂O₂ sensing.