Generation of Transparent Oxygen Evolution Electrode Consisting of Regularly Ordered Nanoparticles from Self-Assembly Cobalt Phthalocyanine as a Template

Hierarchical Nanostructures of Iron Phthalocyanine Nanowires Coated on Nickel Foam as Catalysts for the Oxygen Evolution Reaction

In this paper, iron phthalocyanine nanowires on a nickel foam (FePc@NF) composite catalyst were prepared by a facile solvothermal approach. The catalyst showed good electrochemical oxygen evolution performance. In 1.0 M KOH electrolyte, 289 mV low overpotential and 49.9 mV dec-1 Tafel slope were seen at a current density of 10 mA cm-2. The excellent electrochemical performance comes from the homogeneous dispersion of phthalocyanine nanostructures on the surface of the nickel foam, which avoids the common agglomeration problem of such catalysts and provides a large number of active sites for the OER reaction, thus improving the catalytic performance of the system.

Switchable molecular electrocatalysis

We demonstrate a switchable electrocatalysis mechanism modulated by hydrogen bonding interactions in ligand geometries. By manipulating these geometries, specific electrochemical processes at a single catalytic site can be selectively and precisely activated or deactivated. The α geometry enhances dioxygen electroreduction (ORR) while inhibiting protium redox processes, with the opposite effect seen in the β geometry. Intramolecular hydrogen bonding in the α geometry boosts electron density at the catalytic center, facilitating a shift of ORR to a 4-electron pathway. Conversely, the β geometry promotes a 2-electron ORR and facilitates electrocatalytic hydrogen evolution through an extensive proton charge assembly; offering a paradigm shift to conventional electrocatalytic principles. The expectations that ligand geometry induced electron density modulations in the catalytic metal centre would have a comparable impact on both ORR and HER has been questioned due to the contrasting reactivity exhibited by α-geometry and β-geometry molecules. This further emphasizes the complex and intriguing nature of the roles played by ligands in molecular electrocatalysis.

Spinel MnCo2 O4 Nanoparticles Supported on Three-Dimensional Graphene with Enhanced Mass Transfer as an Efficient Electrocatalyst for the Oxygen Reduction Reaction

The rational design of highly efficient and durable oxygen reduction reaction (ORR) catalysts is critical for the commercial application of fuel cells. Herein, three-dimensional graphene (3D-G) is synthesized by the template method, which used coal tar pitch as the carbon source and nano MgO as the template. Then, spinel MnCo₂ O₄ is in situ supported on the 3D-G by a facile hydrothermal method, giving MnCo₂ O₄ /3D-G. The resultant MnCo₂ O₄ /3D-G retains the multilayered mesoporous graphene structure where MnCo₂ O₄ nanoparticles are deposited on the inner walls of pores in the 3D-G. The catalyst MnCo₂ O₄ /3D-G shows high electrocatalytic activity with a half-wave potential of 0.81 V versus reversible hydrogen electrode, which is clearly superior to those of MnCo₂ O₄ /reduced graphene oxide (0.78 V), MnCo₂ O₄ /carbon nanotubes (0.74 V), MnCo₂ O₄ /C (0.72 V), and 20 wt % Pt/C (0.80 V). The electron transfer number of MnCo₂ O₄ /3D-G indicates a four-electron process of ORR. The durability test demonstrates that the MnCo₂ O₄ /3D-G catalyst has a much better durability than 20 wt % Pt/C. Our work makes an inspiring strategy to prepare high-performance electrocatalysts for the development of fuel cells.

A Permselective CeOx Coating To Improve the Stability of Oxygen Evolution Electrocatalysts

Highly active NiFeO_x electrocatalysts for the oxygen evolution reaction (OER) suffer gradual deactivation with time owing to the loss of Fe species from the active sites into solution during catalysis. The anodic deposition of a CeO_x layer prevents the loss of such Fe species from the OER catalysts, achieving a highly stable performance. The CeO_x layer does not affect the OER activity of the catalyst underneath but exhibits unique permselectivity, allowing the permeation of OH^- and O₂ through while preventing the diffusion of redox ions through the layer to function as a selective O₂ -evolving electrode. The use of such a permselective protective layer provides a new strategy for improving the durability of electrocatalysts.