RESUMEN
Under the gravity of future socio-economic development, the viability of water electrolysis still hinges on the accessibility of stable earth-abundant electrocatalysts and net energy efficiency. This work emphasizes the design and synthesis of two newly developed cobalt(II) complexes, [Co(HL)2(NCS)2] (Comono) and [Co2(L)3(CH3OH)]ClO4 (Codi), with a (N,O)-donor ligand, HL (2-methoxy-6-(((2-methoxyphenyl)imino)methyl)phenol). The study delves into understanding their structural, morphological, magnetic, and charge transport characteristics. Moreover, the study explores the potential of these complexes in catalyzing hydrogen production through heterogeneous electrocatalysis. The X-ray crystal structure of Comono reveals the octahedral geometry of the Co(II) ion, adopting two HL units and two NCS- units. The Codi complex exhibits a doubly-phenoxo-O-bridged (µ1,1) dinuclear complex, forming a typical octahedral geometry for both the Co(II) centres in coupling with three units of L-. Temperature-dependent magnetic susceptibility measurements showed that all of the Co(II) ion in Comono shows a typical paramagnetic behaviour for high spin octahedral Co(II) ions while the Co(II) centres in Codi are coupled with doubly-phenoxo-bridges bearing weak ferromagnetic characteristics at low temperature. Electron transport properties of the Co(II) complex-mediated Schottky device address the superior carrier mobility (µ) for Codi (9.21 × 10-5) over Comono (2.02 × 10-5 m2 v-1 s-1) with respective transit times of 1.70 × 10-9 and 7.77 × 10-9 s. Additionally, electron impedance spectral analysis supports the lower electrical transport resistance of Codi relative to Comono. The heterogeneous electrocatalytic HER activity of Codi and Comono in 0.1 M KOH shows excellent electrocatalytic efficiency in terms of the various electrochemical parameters. Constant potential electrolysis, multi-cycle CVs, and post-HER analysis reveal the pre-catalytic nature of the complexes, which in turn delivers Co3O4 nanoparticles as the active catalysts for efficient hydrogen evolution.
Asunto(s)
Educación Médica , Educación Médica/métodos , Humanos , Anatomía/educación , Lenguaje , Modelos EducacionalesRESUMEN
A mixed-valence trinuclear cobalt(iii)-cobalt(ii)-cobalt(iii) complex, [(µ-1,3-N3)Co3L(N3)3]·MeOH has been synthesized using a tetradentate N2O2 donor 'reduced Schiff base' ligand, H2L {1,3-bis(2-hydroxybenzylamino)2,2-dimethylpropane} and azide as anionic co-ligand. The complex has been characterised by elemental analysis, IR, UV-vis spectroscopy and single-crystal X-ray diffraction studies etc. The cobalt(iii)-cobalt(ii)-cobalt(iii) skeleton in the complex is non-linear and non-centrosymmetric. The redox behavior of the complex was studied by using Cyclic Voltammetry (CV). The complex is found to be a semiconductor material as confirmed by determining the band gap of this complex by experimental as well as theoretical studies. The band gap in the solid state has been determined experimentally. The conductivity of the synthesized complex based device improves considerably in illumination conditions from the non-illuminated conditions. The complex has also been used to fabricate Schottky barrier diodes.
RESUMEN
In this study, we report the synthetic method of two distinct supramolecular metallogels, namely Mn-BDA and Cd-BDA, using Mn(II) acetate tetrahydrate, Cd(II) acetate dihydrate and butane-1,4-dicarboxylic acid (BDA). DMF, a polar aprotic solvent, was immobilized in both metallogel-networks for their synthesis. The metallogelation of Mn-BDA was successfully attained through the instant mixing of a Mn(II)-source and BDA in DMF solvent media. By applying ultrasonication, a Cd-BDA metallogel was prepared. The stoichiometry of gel-forming components concerning metal salts and the LMWG are accountable to obtain respective stable metallogels. Rheological parameters such as storage modulus (G') and loss modulus (G'') explored the mechanical flexibility of the synthesized metallogels through amplitude and angular frequency sweep experiments. Both the metallogels possess significant mechanical stability, which was determined by monitoring diverse gel-to-sol transition shear strain values (γ%). Distinctive morphological visualizations of both of these metallogels (i.e., Mn-BDA and Cd-BDA) were made via field emission scanning electron microscopic (FESEM) studies, demonstrating a fibrous inter-connected network with a hierarchical self-assembled arrangement for Mn(II)-based metallogels and a typical stacked-flake-like association with hierarchical motifs for Cd(II)-based metallogels. EDAX elemental mapping substantiated the presence of metallogel-forming agents such as individual metal acetate salts, BDA acting as a low-molecular weight gelator, and gel-immobilized solvents such as DMF. Furthermore, Fourier transform infrared spectroscopy and ESI-mass spectroscopy were performed for both these supramolecular metallogels. FT-IR spectroscopic and ESI-mass spectroscopic results clearly substantiate the possible non-covalent supramolecular interactions among basic molecular repeating moieties, i.e., butane-1,4-dicarboxylic acid (the low-molecular weight gelator), individual metal salts and gel-immobilized polar aprotic solvent DMF for the construction of distinct stable supramolecular metallogel-systems. The semiconducting property of the fabricated metallogels was investigated. Two Schottky diodes (SDs) composed of ITO/Cd-BDA/Al and ITO/Mn-BDA/Al in a sandwich pattern with Al serving as the metal electrode were fabricated. Both these metallogel-based devices effectively offer significant semiconducting diode features with non-linear J-V characteristics. The non-ohmic conduction protocol of the fabricated metallogel-based devices was explored. Mn-BDA and Cd-BDA metallogel-based fabricated devices have rectification ratios of 6.67 and 23.50, respectively. The gel-based diode performances were examined by observing the voltage-dependent current density, charge transportation and rectification ratio.
RESUMEN
Here, electrical conductivity and explosive sensing properties of multifunctional chromone-Cd(II)-based coordination polymers (CPs) (1-4) have been explored. The presence of different pseudohalide linkers, thiocyanate ions, and dicyanamide ions resulted in 1D and 3D architecture in the CPs. Thin film devices developed from CPs 1-4 (complex-based Schottky devices, CSD1, CSD2, CSD3, and CSD4, respectively) showed semiconductor behavior. Their conductivity values increased under photo illumination (1.37 × 10-5, 1.85 × 10-5, 1.61 × 10-5, and 2.01 × 10-5 S m-1 under dark conditions and 5.06 × 10-5, 8.78 × 10-5, 7.26 × 10-5, and 10.21 × 10-5 S m-1 under light). The nature of the I-V plots of these thin film devices under light irradiation and dark are nonlinear rectifying, which has been observed in Schottky barrier diodes (SBDs). All four CPs (1-4) exhibited highly selective fluorescence quenching-based sensing properties toward well-known explosives, 2,4-dinitrophenol (DNP) and 2,4,6-trinitrophenol (TNP). The limit of detection (LOD) values are 55, 28, 27, and 31 µM for TNP and 78, 44, 32, and 41 µM for DNP for complexes 1-4, respectively. A structure property correlation has been established to explain optoelectronic and explosive sensing properties.