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Charge transfer dynamics and catalytic performance of a covalently linked hybrid assembly comprising a functionalized cobalt tetraazamacrocyclic catalyst and CuInS <sub/>2</sub> /ZnS quantum dots for photochemical hydrogen production
摘要： Although the cobalt complex, [Co(CR)X2]+ (CR ? 2,12-dimethyl-3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),2,11,13,15-pentaene), has been studied as a catalyst for electro- and photochemical H2 generation and CO2 reduction for more than thirty years, only the unfunctionalized one was used as a free catalyst in bulk solutions. Considering that the immobilization of functionalized molecular catalysts (MCs) on the surface of light harvesting materials through a stable covalent linkage was often an effective strategy to boost the activity of semiconductor/MC hybrid photocatalytic systems, we prepared the first anchoring group-functionalized [Co(CR)X2]+ complex (C1, X ? Br), which bears a (20,60-dicarboxypyridin-40-yl) group at position 15 of the macrocyclic ligand. The covalent attachment of C1 to the surface of CuInS2/ZnS (CISZ) core–shell quantum dots (QDs) afforded the C1@CISZ hybrid assembly. Comparative studies on the visible-light-induced H2 evolution performances of C1@CISZ and the non-bonded reference system comprising the unfunctionalized [Co(CR)Br2]+ complex (C2) and CISZ QDs (denoted as C2+CISZ) revealed that the photocatalytic activity of C1@CISZ was twice to thrice as high as that of C2+CISZ under the same conditions. Appealingly, the isolated C1@CISZ assembly was more stable than the C2+CISZ system in long-term photolysis. Moreover, photoluminescence (PL) and transient absorption (TA) spectroscopic studies demonstrated that covalent immobilization of C1 on the surface of CISZ QDs accelerated the electron transfer from QDs to the catalyst and meanwhile retarded the charge recombination process on the surface of QDs. The evidently improved charge separation efficiency resulted in the higher activity of the hybrid assembly C1@CISZ than that of C2+CISZ for photocatalytic hydrogen production.
关键词： photochemical H2 generation,cobalt complex,photocatalytic hydrogen production,CO2 reduction,charge transfer dynamics,CuInS2/ZnS quantum dots
更新于2025-09-16 10:30:52
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Cobalt complex dye as a novel sensitizer in dye sensitized solar cells
摘要： In this study, cobalt metal complex has been introduced as a novel class of sensitizer for more mechanistic consideration of the photovoltaic conversion efficiency (PCE) of dye sensitized solar cells. UV-Vis spectroscopy of dye illustrates maximum absorption at wavelengths of dye in 498 and 650 nm. TiO2 was used as the photoanode of the cell whose X-ray diffraction spectrum indicates that its crystal phase is anatase (101). Surface morphology of photoanode was also investigated by scanning electron microscopy (SEM) and obviously showed ~25nm TiO2 nanoparticles. The cyclic voltammetry (CV) investigation of Pt-coated fluorine doped tin oxide (FTO) as the counter electrode of the cell indicates redox process on this electrode. Photovoltaic measurements of cobalt complex sensitized solar cell show that the short-circuit current density (JSC), open-circuit voltage (VOC), fill factor (FF%) and photovoltaic conversion efficiency (PCE%) are 48.80 μA.cm-2, 0.7 V, 44% and 0.09% at the air mass 1.5 (100mW.cm-2) irradiation condition, respectively. The high light harvesting efficiency (LHE) (~61%) and high molar absorption coefficient of the cobalt complex dye (12,500 M-1.cm-1) were other optical advantages of the cobalt complex sensitized solar cell. The results indicate the quantum yield of electron injection (φing) which depends on dye structure as a parameter influences the JSC. The pyridine rings conformation in donor part of the cobalt complex dye plays a significant role in φing and subsequently PCE. These findings open a new insight about mechanistic aspects of dye sensitized solar cells efficiency.
关键词： Dye-sensitized solar cell,Photoanode,Dye,Counter electrode,Photovoltaic measurement,Cobalt complex
更新于2025-09-12 10:27:22
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Synthesis, crystal structure, vibrational study, optical properties and Hirshfeld surface analysis of bis(2,6-diaminopyridinium) tetrachloridocobaltate(II) monohydrate
摘要： The title organic–inorganic hybrid compound, (C5H8N3)2[CoCl4]·H2O, was synthesized by slow evaporation at room temperature. Single-crystal X-ray diffraction analysis indicates that the asymmetric unit in this compound consists of one tetrahedral geometry [CoCl4]2-, two protonated organic cations (C5H8N3)+ and one water molecule of crystallization, all of which lie in general positions. In the crystal structure, the inorganic layers are built from tetrachloridocobaltate anions [CoCl4]2- and free water molecules, linked together by O—H…Cl hydrogen bonds. The organic cations are intercalated between the inorganic layers via N—H…Cl hydrogen bonds and form chains through aromatic donor–acceptor interactions. Crystal cohesion is achieved through N—H…Cl, O—H…Cl, N—H…O and C—H…Cl hydrogen bonds between organic cations, inorganic anions and the water molecules building up a three-dimensional network. The functional groups present in the crystal were studied by FTIR spectroscopy. Investigation of the optical properties of the compound confirmed its semiconducting properties by revealing a direct optical band gap at 1.67 eV. Photoluminescence proprieties were also reported. The three-dimensional Hirshfeld surface (3D-HS) analysis and the two-dimensional fingerprint plots (2D-FP) reveal that the structure is dominated by H…Cl/Cl…H and H…H contacts.
关键词： Crystal structure,Hirshfeld surface analysis,Vibrational study,Cobalt complex
更新于2025-09-09 09:28:46