Imidazolatic-Framework Bimetal Electrocatalysts with a Mixed-Valence Surface Anchored on an rGO Matrix for Oxygen Reduction, Water Splitting, and Dye Degradation.

This paper presents a simple strategy for manufacturing bifunctional electrocatalysts-graphene nanosheets (GNS) coated with an ultrafine NiCo-MOF as nanocomposites (denoted NiCo-MOF@GNS) having a N-doped defect-rich and abundant cavity structure through one-pool treatment of metal-organic frameworks (MOFs). The precursors included N-doped dodecahedron-like graphene nanosheets (GNS), in which the NiCo-MOF was encompassed within the inner cavities of the GNS (NiCo-MOF@GNS) at the end or middle portion of the tubular furnace with several graphene layers. Volatile imidazolate N x species were trapped by the NiCo-MOF nanosheets during the pyrolysis process, simultaneously inserting N atoms into the carbon matrix to achieve the defect-rich porous nanosheets and the abundantly porous cavity structure. With high durability, the as-prepared nanomaterials displayed simultaneously improved performance in the oxygen reduction reaction (ORR), the oxygen evolution reaction (OER), and photocatalysis. In particular, our material NiCo-MOF@GNS-700 exhibited excellent electrocatalytic activity, including a half-wave potential of 0.83 V (E ORR, 1/2), a low operating voltage of 1.53 V (E OER, 10) at 10 mA cm-2, a potential difference (ΔE) of 1.02 V between E OER, 10 and E ORR, 1/2 in 0.1 M KOH, and a low band gap of 2.61 eV. This remarkable behavior was due to the structure of the defect-rich porous carbon nanosheets and the synergistic impact of the NPs in the NiCo-MOF, the N-doped carbon, and NiCo-N x . Furthermore, the hollow structure enhanced the conductivity and stability. This useful archetypal template allows the construction of effective and stable bifunctional electrocatalysts, with potential for practical viability for energy conversion and storage.

Modification of the photocatalytic activity of TiO2 by ß-Cyclodextrin in decoloration of ethyl violet dye.

The photocatalytic decoloration of an organic dye, ethyl violet (EV), has been studied in the presence of TiO2 and the addition of ß-Cyclodextrin (ß-CD) with TiO2 (TiO2-ß-CD) under UV-A light irradiation. The different operating parameters like initial concentration of dye, illumination time, pH and amount of catalyst used have also been investigated. The photocatalytic decoloration efficiency is more in the TiO2-ß-CD/UV-A light system than TiO2/UV-A light system. The mineralization of EV has been confirmed by Chemical Oxygen Demand (COD) measurements. The complexation patterns have been confirmed with UV-Visible and FT-IR spectral data and the interaction between TiO2 and ß-CD have been characterized by powder XRD analysis and UV-Visible diffuse reflectance spectroscopy.