Ni Nano-particle Encapsulated in Hollow Carbon Sphere Electrocatalyst in Polymer Electrolyte Membrane Water Electrolyzer

Heteroatom-Doped Metal-Free Carbon Nanomaterials as Potential Electrocatalysts

In recent years, heteroatom-incorporated specially structured metal-free carbon nanomaterials have drawn huge attention among researchers. In comparison to the undoped carbon nanomaterials, heteroatoms such as nitrogen-, sulphur-, boron-, phosphorous-, etc., incorporated nanomaterials have become well-accepted as potential electrocatalysts in water splitting, supercapacitors and dye-sensitized solar cells. This review puts special emphasis on the most popular synthetic strategies of heteroatom-doped and co-doped metal-free carbon nanomaterials, viz., chemical vapor deposition, pyrolysis, solvothermal process, etc., utilized in last two decades. These specially structured nanomaterials’ extensive applications as potential electrocatalysts are taken into consideration in this article. Their comparative enhancement of electrocatalytic performance with incorporation of heteroatoms has also been discussed.

Evaluation of mixed transition metal (Co, Mn, and Cu) oxide electrocatalysts anchored on different carbon supports for robust oxygen reduction reaction in neutral media

Oxygen reduction reaction (ORR) remains a pivotal factor in assessing the overall efficiency of energy conversion and storage technologies. A promising family of ORR electrocatalysts is mixed transition-metal oxides (MTMOs), which have recently gained a growing research interest. In this study, we developed MTMOs with different compositions (designated as A_xB_3−xO₄; A = Cu, B = Co or Mn) anchored on two different carbon supports (activated carbon Vulcan XC-72 (AC) and graphene (G)) for catalyzing ORR in neutral media. Four different MTMO electrocatalysts (i.e., MnO₂–CuO/AC, CoO–CuO/AC, CoO–CuO/G, and MnO₂–CuO/G) were synthesized by a simple and scalable co-precipitation method. We documented the morphology and electrocatalytic properties of MTMO electrocatalysts using transmission and scanning electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectrometer (XPS), energy dispersive X-ray (EDX), and electrochemical techniques. Generally, MTMOs exhibited remarkably high ORR electrocatalytic activity with MTMOs anchored on an activated carbon support outperforming their respective MTMOs anchored on a graphene support, highlighting the importance of the catalyst support in determining the overall ORR activity of electrocatalysts. MnO₂–CuO/AC has the highest diffusion limiting current density (j) value of 4.2 mA cm⁻² at −600 mV (vs. SHE), which is ∼1.1–1.7-fold higher than other tested electrocatalysts (i.e., 3.9, 3.5, and 2.7 mA cm⁻² for CoO–CuO/AC, CoO–CuO/G, and MnO₂–CuO/G, respectively), and slightly lower than Pt/C (5.1 mA cm⁻²) at the same potential value. Moreover, all electrocatalysts exhibited good linearity and parallelism of the Koutechy–Levich (K–L) plots, suggesting that ORR followed first-order reaction kinetics with the number of electrons involved being close to four. Benefiting from their remarkable ORR electrochemical activities and low cost, our results reveal that non-precious MTMOs are efficient enough to replace expensive Pt for broad applications in energy conversion and electrocatalysis in neutral media, such as microbial fuel cells.

Mixed transition metal (Co, Mn, and Cu) oxide electrocatalysts anchored on different carbon supports for oxygen reduction reaction.

Electrocatalytic Imprinted Polymer of N-Doped Hollow Carbon Nanosphere-Palladium Nanocomposite for Ultratrace Detection of Anticancer Drug 6-Mercaptopurine

In this work, a nanohybrid-based imprinted polymer consisting of N-doped hollow carbon nanospheres and palladium is reported for the electroanalysis of ultratrace level of anticancer drug, 6-mercaptopurine, used in the treatment of leukemia. For this, N-doped carbon nanospheres decorated with palladium were first developed, and subsequently, a molecular imprinted polymer layer was grown onto their surfaces. The so-produced silica-embedded nanocomposite was made hollow by etching silica moieties with hydrofluoric acid. Finally, the whole system was doped on an ionic-liquid-modified pencil graphite electrode. The underlying synergistic effect of hollow carbon nanosphere-supported palladium nanoparticles inculcated electrocatalytic action. Notably, all rebinding sites in solid core-shells were confined within the shell, which hampers the effective diffusion of template. However, in this work, an effective diffusion of template across the hollow structure of inner and outer surfaces was observed. Consequently, this rendered approximately 2-fold heterogeneous rate constant as compared to the solid core-shell-based sensor. Differential pulse voltammetric transduction was used for ultratrace detection of 6-mercaptopurine through anodic stripping method. The hollow imprinted sensor revealed a linear dependence of current with concentration range 0.80-70.748 ng mL^-1. The limits of detection 0.11-0.22 ng mL^-1 were realized in water, human blood plasma, urine, and pharmaceuticals. Thus, the proposed sensor demonstrated an attractive sensitivity reproducibility, as well as endurance requisite for the treatment of leukemia patients.

Ag-doped nano magnetic γ-Fe2O3@DA core–shell hollow spheres: an efficient and recoverable heterogeneous catalyst for A3 and KA2 coupling reactions and [3 + 2] cycloaddition

An effective protocol for the fabrication of Ag-doped nano magnetic γ-Fe₂O₃@DA core–shell hollow spheres (h-Fe₂O₃@DA/Ag) by a simple hydrothermal method is demonstrated without any templates in the reaction system.