Taiwo Odedairo

Nanosheets Co3O4 Interleaved with Graphene for Highly Efficient Oxygen Reduction

Efficient yet inexpensive electrocatalysts for oxygen reduction reaction (ORR) are an essential component of renewable energy devices, such as fuel cells and metal-air batteries. We herein interleaved novel Co3O4 nanosheets with graphene to develop a first ever sheet-on-sheet heterostructured electrocatalyst for ORR, whose electrocatalytic activity outperformed the state-of-the-art commercial Pt/C with exceptional durability in alkaline solution. The composite demonstrates the highest activity of all the nonprecious metal electrocatalysts, such as those derived from Co3O4 nanoparticle/nitrogen-doped graphene hybrids and carbon nanotube/nanoparticle composites. Density functional theory (DFT) calculations indicated that the outstanding performance originated from the significant charge transfer from graphene to Co3O4 nanosheets promoting the electron transport through the whole structure. Theoretical calculations revealed that the enhanced stability can be ascribed to the strong interaction generated between both types of sheets.

Activated carbon becomes active for oxygen reduction and hydrogen evolution reactions

We utilized a facile method for creating unique defects in the activated carbon (AC), which makes it highly active for the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). The ORR activity of the defective AC (D-AC) is comparable to the commercial Pt/C in alkaline medium, and the D-AC also exhibits excellent HER activity in acidic solution.

One-pot synthesis of carbon nanotube–graphene hybrids via syngas production

Multi-walled carbon nanotubes (MWCNTs) are limited by entanglement, and it is rather difficult to prevent graphene stacking in a polymer composite. These two challenges can be addressed by developing a MWCNT–graphene hybrid where MWCNTs and graphene are born as twins. We in this study employed a syngas production method using microwave irradiation for a one-pot synthesis of porous, crumpled and loose MWCNT–graphene hybrids, investigated the substrate compositions, measured their performance as electrodes for energy storage devices, and proposed the synthesis mechanisms. A number of hybrids, including MWCNT–graphene, MWCNT–cup-stacked CNT and MWCNT–graphitic nanofiber, were synthesized on Cr–Ni, Fe–Ni and Ni–CeO2 substrates, respectively. TEM analysis shows that the two challenges have been markedly addressed in the hybrids. They performed better in terms of capacitive properties than commercial MWCNTs.

A new approach to nanoporous graphene sheets via rapid microwave-induced plasma for energy applications

We developed a novel approach to the fabrication of three-dimensional, nanoporous graphene sheets featuring a high specific surface area of 734.9 m(2) g(-1) and an ultrahigh pore volume of 4.1 cm(3) g(-1) through a rapid microwave-induced plasma treatment. The sheets were used as electrodes for supercapacitors and for the oxygen reduction reaction (ORR) for fuel cells. Argon-plasma grown sheets exhibited a 44% improvement of supercapacitive performance (203 F g(-1)) over the plasma grown sheets (141 F g(-1)). N-doped sheets with Co3O4 showed an outstanding ORR activity evidenced from the much smaller Tafel slope (42 mV/decade) than that of Pt/C (82 mV/decade), which is caused by the high electrical conductivity of the graphene sheets, the planar N species content and the nanoporous morphology.

Flower-like perovskite LaCr0.9Ni0.1O3−δ–NiO nanostructures: a new candidate for CO2 reforming of methane

We have developed a facile low-cost approach to the fabrication of large-scale flower-like perovskite-type oxides: orthorhombic LaCr0.9Ni0.1O3−δ nanowires. The nanowires (∼76.2%) exhibited higher CO2 conversion than their conventional bulk counterpart (∼40.1%) due to exposure of more active sites. The unique morphological structure of the nanowires enhanced the dispersion of Pd nanoparticles on its edges and surfaces, resulting in excellent performance and stability in CO2 reforming of methane. The Pd decorated LaCr0.9Ni0.1O3−δ nanowires exhibit optimum CO2 and CH4 conversions of ∼98.6% and ∼75.4% at 800 °C. The high turnover frequency (TOF) of CH4 (6.04 s−1) on 1 wt% Pd decorated LaCr0.9Ni0.1O3−δ might be attributed to high dispersion of Pd species on the nanowires.

Hexagonal Sphericon Hematite with High Performance for Water Oxidation

A cost-effective hexagonal sphericon hematite with predominant (110) facets for the oxygen evolution reaction (OER) is demonstrated. Sequential incorporation of near-atomic uniformly distributed Ce species and Ni nanoparticles into selected sites of the hematite induces a complex synergistic integration phenomenon that enhances the overall catalytic OER performance. This cheap hexagonal sphericon hematite (Fe ≈ 98%) only needs a small overpotential (η) of 0.34 V to reach 10 mA cm-2 , superior to commercial IrO2 and more expensive Co-, Ni-, and Li-based electrocatalysts.

Revisiting Oxidative Dehydrogenation of Ethane by W Doping into MoVMn Mixed Oxides at Low Temperature

The catalytic performance of MoVMnW mixed oxides was investigated in the oxidative dehydrogenation of ethane at three different reaction temperatures (235, 255, and 275°C) using oxygen as an oxidant. The catalysts were characterized by using X-ray diffraction, temperature-programmed reduction, and scanning electron microscopy. The MoVMnW mixed oxide catalyst showed the 70–90% of ethylene selectivity at the reaction temperatures. However, a significant decrease in the selectivity of ethylene was observed by increasing the reaction temperature from 235°C to 275°C.