Beads‐on‐string hierarchical structured electrocatalysts for efficient oxygen reduction reaction

Abstract

Rational design of hierarchically structured electrocatalysts is particularly important for electrocatalytic oxygen reduction reaction (ORR). Here, ZIF-67 crystals are stringed on core-shell Ag@C nanocables using a coordinationmodulated process. Upon pyrolysis, Ag@C strings of Co nanoparticles embedded with three-dimensional porous carbon with beads-on-string hierarchical structures are developed. Due to the advantages of the rich electrochemical active sites of Co-based "beads" and the efficient electron transfer pathways via Ag@C "strings," the resultant NH 3

Core–Shell ZIF-8@ZIF-67-Derived Cobalt Nanoparticle-Embedded Nanocage Electrocatalyst with Excellent Oxygen Reduction Performance for Zn–Air Batteries

“…Relevant studies have shown that ZIF-67 can be used to prepare various Co-based carbon nanomaterials through high-temperature pyrolysis, including heteroatom-doped and metal- or metal-oxide-modified porous carbon. − However, a pure ZIF-67 derivative has the disadvantages of a low specific surface area with poor porosity, seriously impacting the dispersion of active sites and the reactive substances’ transport, leading to a reduction in ORR reactivity. Therefore, optimizing the structure of the ZIF-67 precursor to obtain layered porous hollow carbon materials can effectively enhance the dispersion of active sites and substrate transport, significantly improving the ORR catalytic performance of carbon materials. − Previous studies have concentrated on the two-step growth of ZIFs onto nanofibers. However, those active sites on the material surfaces will be lost easily, and the active sites inside are difficult to contact the reaction substrate, which results in the degradation of the electrochemistry performance of the material.…”

Hybrid Co/CoO/Ce-Doped WO3 Nanoparticles on a ZIF-L Framework as Bifunctional Oxygen Electrocatalysts for Rechargeable Zinc–Air Batteries

“…Apart from the superior ORR activity, the selectivity of PZF-2-700 was detected using RDE at different rotation rates (Figure b). Koutecký–Levich (K–L) plots exhibit good linearity under various potentials, reflecting that the ORR abides by the first-order reaction kinetics with the concentration of dissolved oxygen. , The electron transfer number of per oxygen was calculated to be ∼4.0 at different potentials, as determined using the K–L plots (Figure c). − The average electron transfer number was further verified to be 3.9–4.0 through the rotating ring–disk electrode measurement (Figure S5). , In addition, the reaction kinetics of the catalyst was evaluated by the Tafel slope.…”

“…Koutecky−Levich (K−L) plots exhibit good linearity under various potentials, reflecting that the ORR abides by the first-order reaction kinetics with the concentration of dissolved oxygen. 54,55 The electron transfer number of per oxygen was calculated to be ∼4.0 at different potentials, as determined using the K−L plots (Figure 4c). 54−56 The average electron transfer number was further verified to be 3.9−4.0 through the rotating ring−disk electrode measurement (Figure S5).…”

Compositional engineering of HKUST‐1/sulfidized NiMn‐LDH on functionalized MWCNTs as remarkable bifunctional electrocatalysts for water splitting

“…In this regard, preferred catalysts are those that can enable a dual function and thus operate efficiently in both OER and HER processes 15,16 . Although some porous materials and sulfides based on transition metals showed excellent behavior in electrochemical water splitting, 17–19 there are some challenges associated with the use of these materials (i.e., leaching, low conductivity, and agglomeration) that impede their applications for HER and OER 20,21 . The solution for overcoming these problems and improving the overall electrocatalytic behavior consists of adding carbonaceous components, such as nanotubes or reduced graphene oxide, to transition‐metal‐based electrocatalytic systems 22 …”