Carbon composites with embedded metal/metal oxides represent a group of versatile electrochemical catalysts that has attracted extensive research attention. However, the beauty of this concept is marred by the severe carbon evaporation and the aggregation of metal species during their synthetic process, leading to the diminishment in active sites and catalytic durability. To address this issue, this study demonstrates the feasibility of utilizing Al2 O3 nanolayer to trap volatile carbon and nitrogen species and alleviate the aggregation of Co species during the pyrolysis of the Zn/Co-ZIFs (ZIF = zeolitic imidazolate framework). With the confinement effect of an Al2 O3 nanolayer, the derived Co3 O4 -embedded N-doped porous carbon grown on carbon cloth presents outstanding bifunctional catalytic activity with a small potential difference of 787 mV between the half-wave potential of the oxygen reduction reaction and an overpotential at 10 mA cm-2 of the oxygen evolution reaction. More impressively, an advanced flexible rechargeable zinc-air battery in all-solid-state configuration is assembled, which achieves the maximum power density of 72.4 mW cm-3 and good cycling stability. The insights produced in this work will provide guidance for the rational design of metal/carbon hybrid catalysts and low-cost renewable energy systems.

A Confinement Strategy for Stabilizing ZIF-Derived Bifunctional Catalysts as a Benchmark Cathode of Flexible All-Solid-State Zinc-Air Batteries.

Defect-rich carbon based bimetallic oxides with abundant oxygen vacancies as highly active catalysts for enhanced 4-aminobenzoic acid ethyl ester (ABEE) degradation toward peroxymonosulfate activation

Recent advances in carbonized non-noble metal–organic frameworks for electrochemical catalyst of oxygen reduction reaction

In this work, atomically substituted three-dimensionally ordered macroporous (3DOM) spinels based on Co and Mn (MnCo2O4 and CoMn2O4) were synthetized and used as cathodic electrocatalysts in a primary Zn-air battery. Scanning/transmission electron microscopy images show a 3DOM structure for both materials. Skeleton sizes of 114.4 and 140.8 nm and surface areas of 65.3 and 74.6 m2 g-1 were found for MnCo2O4 and CoMn2O4, respectively. The increase in surface area and higher presence of Mn3+ and Mn4+ species in the CoMn2O4 3DOM material improved battery performance with a maximum power density of 101.6 mW cm-2 and a specific capacity of 1440 mA h g-1, which shows the highest battery performance reported to date using similar spinel materials. The stability performance of the electrocatalyst was evaluated in half-cell and battery cell systems, showing the higher durability of CoMn2O4, which was related to its better capability to perform the electrocatalytic process as adsorption, electron transfer, and desorption. It was found through density functional theory calculations that the CoMn2O4 spinel has a higher density of states in the Fermi level vicinity and better conductivity. Finally, the unique shape of 3DOM spinels promoted a high interaction between electroactive species and catalytic sites, making them suitable for oxygen reduction reaction applications.

Three-Dimensional-Order Macroporous AB2O4 Spinels (A, B =Co and Mn) as Electrodes in Zn–Air Batteries

Oxygen evolution reaction (OER) is one of the key electrocatalysis technologies for the development of renewable energy conversion and storage systems like water splitting, metal-air batteries, and fuel cells. For the large-scale application of these technologies, highly efficient, low cost and stable electrocatalysts are very important. Recently, non-noble metal-based OER electrocatalyst has drawn fabulous research interest. Albeit, it may be difficult to include all the studies, this review aims to look over the recent progress and offer a comprehensive insight toward the OER. It begins with a fundamental introduction to the electrochemistry of OER electrocatalyst including the synthesis, and mechanism. In this review, a comprehensive investigation is made on various types of nanostructured materials including Co, Ni, Mn, Fe, Cu, and Zn-based transition metal oxide and multi-metal oxides such as spinels, perovskites, and layered double hydroxides. The crucial factors that are used to tune the activity of the catalyst towards OER are summarized, including nanostructure development, phase, morphology, crystal facet, defect, mixed-metal, and strain engineering for metal oxide, heteroatom doping, topological defects, and formation of metal-N-C composites. Finally, major applications, the current states challenges, and some perspectives for non-noble-metal-based OER electrocatalysts are discussed. This review will help to explore and develop better catalysts and units for practical applications and will offer a basic understanding of the OER process along with the standard parameters to evaluate the performance.

A comprehensive review on the recent developments in transition metal-based electrocatalysts for oxygen evolution reaction

https://hal.archives-ouvertes.fr/hal-02882257/document

Flower-like NiCo2O4–CN as efficient bifunctional electrocatalyst for Zn-Air battery

Developing a highly active and cost-effective cathode electrocatalyst with strong stability for oxygen reduction reaction (ORR) is extremely necessary. In this work, we reported a facile synthetic path to prepare a hybrid nanostructure formed of nitrogen-doped Ketjenblack carbon (N-KC) supported Co3O4 nanoparticles (Co3O4/N-KC), which could be used as a promising and stable electrocatalyst for ORR. Compared with the physical mixture of Co3O4 and N-KC and pure N-KC samples, the resulting Co3O4/N-KC nanohybrid afforded remarkably superb ORR activity with a half-wave potential of 0.82 V (vs. reversible hydrogen electrode, RHE) and a limiting current density of 5.70 mA cm-2 in KOH solution (0.1 M). Surprisingly, the Co3O4/N-KC sample possessed a similar electrocatalytic activity but better durability to the 20 wt% Pt/C catalyst. The remarkable ORR activity of the Co3O4/N-KC nanohybrid was mainly due to the strong coupling effect between Co3O4 and N-KC, the N species dopant, high electroconductivity, and the large BET surface area. Our work enlightens the exploitation of advanced Co3O4/carbon hybrid material alternative to the Pt-based electrocatalysts.

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Nitrogen-doped Ketjenblack Carbon Supported Co3O4 Nanoparticles as a Synergistic Electrocatalyst for Oxygen Reduction Reaction

Yolk−shell Prussian blue analogues hierarchical microboxes: Controllably exposing active sites toward enhanced cathode performance for lithium ion batteries

Shengbo Han

Papers

Flower-like NiCo2O4–CN as efficient bifunctional electrocatalyst for Zn-Air battery

Nitrogen-doped Ketjenblack Carbon Supported Co3O4 Nanoparticles as a Synergistic Electrocatalyst for Oxygen Reduction Reaction

Yolk−shell Prussian blue analogues hierarchical microboxes: Controllably exposing active sites toward enhanced cathode performance for lithium ion batteries

Shape‐Controlled Synthesis of NiCo2O4‐rGO as Bifunctional Electrocatalyst for Zn‐Air Battery

Tuning hydrogen binding energy by interfacial charge transfer enables pH-universal hydrogen evolution catalysis of metal phosphides