Forest of Pt–Au–Ag tri-metallic nanodendrites as an efficient electrocatalyst for methanol oxidation reaction

International audienceForests of trimetallic nanodendrites composed of Pt, Au, and Ag have been synthesized and their catalytic performances with regard to the methanol oxidation reaction (MOR) were evaluated. Analysis based on elemental mapping revealed homogeneous incorporation of Pt, Au, and Ag throughout the nanodendrite and single crystalline structure. These materials proved active for MOR, with improved electrocatalytic performances with regards to Pt in terms of both overpotential and stability

Enhanced Efficiency and Stability of an Aqueous Lead-Nitrate-Based Organometallic Perovskite Solar Cell

We investigate the stability of an active organometallic perovskite layer prepared from a two-step solution procedure, including spin coating of aqueous lead nitrate (Pb(NO3)(2)) as a Pb2+ source and sequential dipping into a methylammonium iodide (CH3NH3I) solution. The conversion of CH3NH3PbI3 from a uniform Pb(NO3)2 layer generates PbI2-free and large-grain perovskite crystallites owing to an intermediate ion exchange reaction step, resulting in improved humidity resistance and, thereby, improved long-term stability with 93% of the initial power conversion efficiency (PCE) after a period of 20 days. The conventional fast-converted PbI2-dimethylformamide solution system leaves small amounts of intrinsic PbI2 residue on the resulting perovskite and MAPbI(3) crystallites with uncontrollable sizes. This accelerates the generation of PbI2 and the decomposition of the perovskite layer, resulting in poor stability with less than 60% of the initial PCE after a period of 20 days.1142sciescopu

In Situ Dynamic Nanostructuring of the Cu-Ti Catalyst-Support System Promotes Hydrogen Evolution under Alkaline Conditions

We report an interesting case of in situ dynamic nanostructuring of catalyst and support under hydrogen evolution conditions in basic media. When solution-grown CuO nanoplates on titanium substrates are subjected to hydrogen evolution reaction, besides the reduction of CuO to metallic Cu nanoplates, both catalyst and support simultaneously undergo a nanostructuring process. The process is driven by the dissolution-redeposition of Cu and the alkaline etching of the titanium support. The morphology of the resulting nanocomposite material consists of a porous matrix made of ultrasmall Cu nanocrystals and amorphous TiOx nanoparticles. Interestingly, the nanostructuring of the catalyst can be finely controlled by varying the applied potential. Such a process leads to a 5.4-fold improvement in the catalyst activity, which is attributed not only to its large active surface area (formed upon nanostructuring), but also to an improved water dissociation activity, provided by the in situ formation of TiOx nanoparticles. The final catalyst exhibits -10 mA/cm2 of current density at a small overpotential of -108 mV and a long-term operational stability up to 50 h. Density functional theory calculations show that the co-presence of Cu and TiO2 nanoparticles optimizes the free energy of hydrogen adsorption in the final catalyst. Our work highlights the importance of studying the dynamic evolution of catalysts under operational conditions and choice of proper support that enhances the catalyst activity

Electrochemical properties of anodized copper hydroxide nanostructures

Here, we report room temperature growth of one-dimensional copper hydroxide, Cu(OH)2 nanostructures viz., nanoneedles (NNs), nanoleafs (NLs) and nanorods (NRs) from NaOH, LiOH and NaOH+ LiOH aqueous electrolyte solutions, respectively, employing a simple and cost-effective chemical anodization process. Structural elucidation and morphological evolution studies are elaborated thoroughly. Morphology inspired evolution of specific capacitance is estimated using cyclic-voltammogram and discharge measurements wherein, due to a relatively higher total charges and the least charge transfer resistance, in electrode with NRs morphology paved remarkable electrochemical performance compared to electrodes of NNs and NLs morphologies

Topochemical Transformation of Two-Dimensional VSe2 into Metallic Nonlayered VO2 for Water Splitting Reactions in Acidic and Alkaline Media

The engineering of the structural and morphological properties of nanomaterials is a fundamental aspect to attain desired performance in energy storage/conversion systems and multifunctional composites. We report the synthesis of room temperature-stable metallic rutile VO2 (VO2 (R)) nanosheets by topochemically transforming liquid-phase exfoliated VSe2 in a reductive Ar-H2 atmosphere. The asproduced VO2 (R) represents an example of two-dimensional (2D) nonlayered materials, whose bulk counterparts do not have a layered structure composed by layers held together by van der Waals force or electrostatic forces between charged layers and counterbalancing ions amid them. By pretreating the VSe2 nanosheets by O-2 plasma, the resulting 2D VO2 (R) nanosheets exhibit a porous morphology that increases the material specific surface area while introducing defective sites. The assynthesized porous (holey)-VO2 (R) nanosheets are investigated as metallic catalysts for the water splitting reactions in both acidic and alkaline media, reaching a maximum mass activity of 972.3 A g(-1) at -0.300 V vs RHE for the hydrogen evolution reaction (HER) in 0.5 M H2SO4 (faradaic efficiency = 100%, overpotential for the HER at 10 mA cm(-2) = 0.184 V) and a mass activity (calculated for a non 100% faradaic efficiency) of 745.9 A g(-1) at +1.580 V vs RHE for the oxygen evolution reaction (OER) in 1 M KOH (overpotential for the OER at 10 mA cm(-2) = 0.209 V). By demonstrating proof-of-concept electrolyzers, our results show the possibility to synthesize special material phases through topochemical conversion of 2D materials for advanced energy-related applications

Improved Photoelectrochemical Cell Performance of Tin Oxide with Functionalized Multiwalled Carbon Nanotubes–Cadmium Selenide Sensitizer

Here we report functionalized multiwalled carbon nanotubes (<i>f</i>-MWCNTs)–CdSe nanocrystals (NCs) as photosensitizer in photoelectrochemical cells, where <i>f</i>-MWCNTs were uniformly coated with CdSe NCs onto SnO₂ upright standing nanosheets by using a simple electrodeposition method. The resultant blended photoanodes demonstrate extraordinary electrochemical properties including higher Stern–Volmer constant, higher absorbance, and positive quenching, etc., caused by more accessibility of CdSe NCs compared with pristine SnO₂–CdSe photoanode. Atomic and weight percent changes of carbon with <i>f</i>-MWCNTs blending concentrations were confirmed from the energy dispersive X-ray analysis. The morphology images show a uniform coverage of CdSe NCs over <i>f</i>-MWCNTs forming a core–shell type structure as a blend. Compared to pristine CdSe, photoanode with <i>f</i>-MWCNTs demonstrated a 257% increase in overall power conversion efficiency. Obtained results were corroborated by the electrochemical impedance analysis. Higher scattering, more accessibility, and hierarchical structure of SnO₂-<i>f</i>-MWCNTs-blend–CdSe NCs photoanode is responsible for higher (a) electron mobility (6.89 × 10^–4 to 10.89 × 10^–4 cm² V^–1 S^1–), (b) diffusion length (27 × 10^–6), (c) average electron lifetime (32.2 ms), and transit time (1.15 ms)

Proceedings of National Conference on Relevance of Engineering and Science for Environment and Society

This conference proceedings contains articles on the various research ideas of the academic community and practitioners presented at the National Conference on Relevance of Engineering and Science for Environment and Society (R{ES}2 2021). R{ES}2 2021 was organized by Shri Pandurang Pratishthan’s, Karmayogi Engineering College, Shelve, Pandharpur, India on July 25th, 2021. Conference Title: National Conference on Relevance of Engineering and Science for Environment and SocietyConference Acronym: R{ES}2 2021Conference Date: 25 July 2021Conference Location: Online (Virtual Mode)Conference Organizers: Shri Pandurang Pratishthan’s, Karmayogi Engineering College, Shelve, Pandharpur, India