Co-MOF as a sacrificial template: manifesting a new Co₃O₄/TiO₂ system with a p–n heterojunction for photocatalytic hydrogen evolution

Abstract

The present work reports a novel method of preparing elusive Co 3 O 4 /TiO 2 p-n heterojunction using Co-based metal organic frameworks (Co-MOFs) as TiO 2 -absorbent cum sacrificial template for nanocomposite formation. Four new Co-MOFs based on a bispyrazole ligand and different carboxylic acids, with wide variety of dimensionality, porosity and surface characteristics, were exploited for this purpose. We detail here, the synthesis of cobalt MOFs using hydro(solvo)thermal method and structural characterization by single crystal X-ray diffraction (XRD). We have also successfully demonstrated our strategy of using MOFs for fabricating superior p-n diode-type Co 3 O 4 /TiO 2 hetero-nanocomposites for photocatalytic hydrogen production. The characterization results suggested that the nanocomposites consisted of highly crystalline desired anatase TiO 2 nanoparticles and spinel Co 3 O 4 -like species. The nanocomposite with 2 wt% Co loading exhibited the maximum photoactivity with hydrogen evolution rate of ~7 mmol g −1 h −1 under UV-vis light irradiation. The above results indicate that the present preparative strategy is an amenable route for the synthesis of desirable synergistic photocatalysts joining a remarkable reactivity relevant to the solar energy conversion.

SnO2 -TiO2 structures and the effect of CuO, CoO metal oxide on photocatalytic hydrogen production

“…42,44 On the other hand, the holes photogenerated in the VB of ST material are transferred to CoO, where two routes of charge transfer also take place: one that improves the oxidation process and the other where photogenerated holes are captured by Co 3 O 4 nanoparticles. 16,17,45,46 (Scheme 1d). Thus, Scheme 1.…”

Two-Dimensional Materials and Composites as Potential Water Splitting Photocatalysts: A Review

“…Numerous MOF-based catalyst materials have been synthesized, characterized and upgraded for photocatalytic water splitting reactions in recent times [160,161] with a focus to develop novel and feasible bi-functional promoters to make the concept of commercial solar hydrogen production from water a practical reality [162]. The standard practices to convert MOFs into practical photocatalysts comprise of inclusion of light-sensitive building blocks into the MOF backbone for instance aminoterephthalates [163,164] and porphyrins [165], Doping with any active metal or noble metal in order to enhance catalytic capacities [166], inorganic nano-particles encapsulated in MOFs [167], assembling ternary composites and introduction of electron donor or trapping materials to prevent charge recombination challenges [168]. A primary perspective of efforts in this regard will be presented herewith.…”

Nano Metal‐Organic Framework‐Derived Inorganic Hybrid Nanomaterials: Synthetic Strategies and Applications

“…In addition to transmetalation, seed‐mediated growth techniques are other simple and effective methods to prepare diverse core–shell NMOF templates that can be used as sacrificial templates for the preparation of mixed oxide core–shell structures, such as Fe 2 O 3 @TiO 2 , Cr 2 O 3 @TiO 2 , Co 3 O 4 @TiO 2 , Co 3 O 4 @NiCo 2 O 4 , and CeO 2 @Co 3 O 4 . Considering the formation of crystals in solution involves nucleation accompanied by growth, seclusion of the two events (nucleation and growth) is required for the production of monodisperse particles .…”