Recent Advances in Electrochemical Oxygen Reduction to H2O2: Catalyst and Cell Design

Copyright © 2020 American Chemical Society. Electrochemical production of H2O2 from O2 is a promising alternative to the energy-intensive anthraquinone process that is currently used as an industry standard. Although most research on the oxygen reduction reaction (ORR) has focused on the 4-electron pathway to water relevant to fuel cells, the 2-electron ORR to produce H2O2 is also of significant commercial interest. The first half of this Perspective deals with the progress made in developing noble metal, carbon-based, and single-atom electrocatalysts and highlights the design strategies employed to obtain high selectivity toward H2O2. The second half addresses the challenges of large-scale production and how results obtained using a rotating ring disk electrode (RRDE) can be translated into commercially viable flow cells. This Perspective focuses on the design of catalysts and cells that will enable industrial-scale electrochemical H2O2 production.11sci

Molecular origin of AuNPs-induced cytotoxicity and mechanistic study

Abstract Gold nanoparticles (AuNPs) with diverse physicochemical properties are reported to affect biological systems differently, but the relationship between the physicochemical properties of AuNPs and their biological effects is not clearly understood. Here, we aimed to elucidate the molecular origins of AuNP-induced cytotoxicity and their mechanisms, focusing on the surface charge and structural properties of modified AuNPs. We prepared a library of well-tailored AuNPs exhibiting various functional groups and surface charges. Through this work, we revealed that the direction or the magnitude of surface charge is not an exclusive factor that determines the cytotoxicity of AuNPs. We, instead, suggested that toxic AuNPs share a common structural characteristics of a hydrophobic moiety neighbouring the positive charge, which can induce lytic interaction with plasma membrane. Mechanistic study showed that the toxic AuNPs interfered with the formation of cytoskeletal structure to slow cell migration, inhibited DNA replication and caused DNA damage via oxidative stress to hinder cell proliferation. Gene expression analysis showed that the toxic AuNPs down-regulated genes associated with cell cycle processes. We discovered structural characteristics that define the cytotoxic AuNPs and suggested the mechanisms of their cytotoxicity. These findings will help us to understand and to predict the biological effects of modified AuNPs based on their physicochemical properties

Zeolitic Imidazole Framework Sacrificial Template-Assisted Synthesis of NiCoP Nanocages Doped with Multiple Metals for High-Performance Hybrid Supercapacitors

Metal phosphides have great potential for electrochemical energy-storage devices and electrocatalysis. Although monometallic and bimetallic phosphides have been extensively studied, the preparation of more complex metal phosphides remains challenging and it is necessary to further expand the available design space. Herein, we report a universal method to dope various metal cations into NiCoP nanocages (M-NiCoP, M = Al, Cu, Cr, Zn). Interestingly, the method can also be expanded to allow the incorporation of two to four metal dopants simultaneously (AlCu-NiCoP, AlZn-NiCoP, CrZn-NiCoP, AlCrCu-NiCoP, AlCrCuZn-NiCoP). To investigate the effect of incorporating multiple dopants, AlCu-NiCoP was used as the electrode material for supercapacitors, showing enhanced capacity and cycling stability compared to Al-NiCoP, Cu-NiCoP, and NiCoP electrodes. The superior electrochemical performance is attributed to the increased number of active sites, improved ion-diffusion kinetics, and a modulated electronic structure. An aqueous hybrid supercapacitor with AlCu-NiCoP as the positive electrode and activated carbon as the negative electrode was assembled and demonstrated a high energy density of 62.8 Wh kg(-1) at a power density of 750 W kg(-1) with good cycling stability.

Robust Room Temperature Ferromagnetism In Cobalt Doped Graphene by Precision Control of Metal Ion Hybridization

© 2022 Wiley-VCH GmbH.Graphene-based magnetic materials exhibit novel properties and promising applications in the development of next-generation spintronic devices. Modern synthesis techniques have paved the way to design precisely the local environments of metal atoms anchored onto a nitrogen-doped graphene matrix. Herein, it is demonstrated that grafting cobalt (Co) into the graphene lattice induces robust and stable room-temperature ferromagnetism. These comprehensive experiments and first-principles calculations unambiguously identify that the mechanism for this unusual ferromagnetism is π-d orbital hybridization between Co dxz and graphene pz orbitals. Here, it is found that the magnetic interactions of Co–carbon ions are mediated by the spin-polarized graphene pz orbitals, and room temperature ferromagnetism can be stabilized by electron doping. It is also found that the electronic structure near the Fermi level, which sets the nature of spin polarization of graphene pz bands, strongly depends on the local environment of the Co moiety. This is the crucial, previously missing, ingredient that enables control of the magnetism. Overall, these observations unambiguously reveal that engineering the atomic structure of metal-embedded graphene lattices through careful d to p orbital interactions opens a new window of opportunities for developing graphene-based spintronics devices.N

Self-Assembly of Monodisperse Starburst Carbon Spheres into Hierarchically Organized Nanostructured Supercapacitor Electrodes

We report a three-dimensional (3D) porous carbon electrode containing both nanoscale and microscale porosity, which has been hierarchically organized to provide efficient ion and electron transport. The electrode organization is provided via the colloidal self-assembly of monodisperse starburst carbon spheres (MSCSs). The periodic close-packing of the MSCSs provides continuous pores inside the 3D structure that facilitate ion and electron transport (electrode electrical conductivity ∼0.35 S m^–1), and the internal meso- and micropores of the MSCS provide a good specific capacitance. The capacitance of the 3D-ordered porous MSCS electrode is ∼58 F g^–1 at 0.58 A g^–1, 48% larger than that of disordered MSCS electrode at the same rate. At 1 A g^–1 the capacitance of the ordered electrode is 57 F g^–1 (95% of the 0.24 A g^–1 value), which is 64% greater than the capacitance of the disordered electrode at the same rate. The ordered electrode preserves 95% of its initial capacitance after 4000 charging/discharging cycles

Reversible and cooperative photoactivation of single-atom Cu/TiO 2 photocatalysts

© 2019, The Author(s), under exclusive licence to Springer Nature Limited. The reversible and cooperative activation process, which includes electron transfer from surrounding redox mediators, the reversible valence change of cofactors and macroscopic functional/structural change, is one of the most important characteristics of biological enzymes, and has frequently been used in the design of homogeneous catalysts. However, there are virtually no reports on industrially important heterogeneous catalysts with these enzyme-like characteristics. Here, we report on the design and synthesis of highly active TiO 2 photocatalysts incorporating site-specific single copper atoms (Cu/TiO 2 ) that exhibit a reversible and cooperative photoactivation process. Our atomic-level design and synthetic strategy provide a platform that facilitates valence control of co-catalyst copper atoms, reversible modulation of the macroscopic optoelectronic properties of TiO 2 and enhancement of photocatalytic hydrogen generation activity, extending the boundaries of conventional heterogeneous catalysts11sci

Synthesis of nanostructured P2-Na 2/3 MnO 2 for high performance sodium-ion batteries

© The Royal Society of Chemistry. We report a facile two-step method to synthesize nanostructured P2-Na 2/3 MnO 2 via ligand exchange and intercalation of sodium ions into ultrathin manganese oxide nanoplates. Sodium storage performance of the synthesized material shows a high capacity (170 mA h g −1 ) and an excellent rate performance11sci