Carbon-based nanomaterials have been widely used as catalysts or catalyst supports in the chemical industry or for energy or environmental applications due to their fascinating properties. High surface areas, tunable porosity, and functionalization are considered to be crucial to enhance the catalytic performance of carbon-based materials. Recently, the newly emerging metal–organic frameworks (MOFs) built from metal ions and polyfunctional organic ligands have proved to be promising self-sacrificing templates and precursors for preparing various carbon-based nanomaterials, benefiting from their high BET surface areas, abundant metal/organic species, large pore volumes, and extraordinary tunability of structures and compositions. In comparison with other carbon-based catalysts, MOF-derived carbon-based nanomaterials have great advantages in terms of tailorable morphologies and hierarchical porosity and easy functionalization with other heteroatoms and metal/metal oxides, which make them highly efficient as...

Development of MOF-Derived Carbon-Based Nanomaterials for Efficient Catalysis

A comprehensive review of recent advances in the field of oxygen reduction electrocatalysis utilizing nonprecious metal (NPM) catalysts is presented Progress in the synthesis and characterization of pyrolyzed catalysts, based primarily on the transition metals Fe and Co with sources of N and C, is summarized Several synthetic strategies to improve the catalytic activity for the oxygen reduction reaction (ORR) are highlighted Recent work to explain the active-site structures and the ORR mechanism on pyrolyzed NPM catalysts is discussed Additionally, the recent application of Cu-based catalysts for the ORR is reviewed Suggestions and direction for future research to develop and understand NPM catalysts with enhanced ORR activity are provided

Nonprecious Metal Catalysts for Oxygen Reduction in Heterogeneous Aqueous Systems

Currently, developing nonprecious-metal catalysts to replace Pt-based electrocatalysts in fuel cells has become a hot topic because the oxygen reduction reaction (ORR) in fuel cells often requires platinum, a precious metal, as a catalyst, which is one of the major hurdles for commercialization of the fuel cells. Recently, the newly emerging metal-organic frameworks (MOFs) have been widely used as self-sacrificed precursors/templates to fabricate heteroatom-doped porous carbons. Here, the recent progress of MOF-derived, heteroatom-doped porous carbon catalysts for ORR in fuel cells is systematically reviewed, and the synthesis strategies for using different MOF precursors to prepare heteroatom-doped porous carbon catalysts, including the direct carbonization of MOFs, MOF and heteroatom source mixture carbonization, and MOF-based composite carbonization are summarized. The emphasis is placed on the precursor design of MOF-derived metal-free catalysts and transition-metal-doped carbon catalysts because the MOF precursors often determine the microstructures of the derived porous carbon catalysts. The discussion provides a useful strategy for in situ synthesis of heteroatom-doped carbon ORR electrocatalysts by rationally designing MOF precursors. Due to the versatility of MOF structures, MOF-derived porous carbons not only provide chances to develop highly efficient ORR electrocatalysts, but also broaden the family of nanoporous carbons for applications in supercapacitors and batteries.

Recent Progress in MOF-Derived, Heteroatom-Doped Porous Carbons as Highly Efficient Electrocatalysts for Oxygen Reduction Reaction in Fuel Cells

Engineering nanostructures of PGM-free oxygen-reduction catalysts using metal-organic frameworks

The oxygen reduction reaction (ORR) is the core reaction of numerous sustainable energy-conversion technologies such as fuel cells and metal-air batteries. It is crucial to develop a cost-effective, highly active, and durable electrocatalysts for ORR to overcome the sluggish kinetics of four electrons pathway. In recent years, the carbon-based electrocatalysts derived from metal-organic frameworks (MOFs) have attracted tremendous attention and have been shown to exhibit superior catalytic activity and excellent intrinsic properties such as large surface area, large pore volume, uniform pore distribution, and tunable chemical structure. Here in this review, the development of MOF-derived heteroatom-doped carbon-based electrocatalysts, including non-metal (such as N, S, B, and P) and metal (such as Fe and Co) doped carbon materials, is summarized. It furthermore, it is demonstrated that the enhancement of ORR performance is associated with favorably well-designed porous structure, large surface area, and high-tensity active sites. Finally, the future perspectives of carbon-based electrocatalysts for ORR are provided with an emphasis on the development of a clear mechanism of MOF-derived non-metal-doped electrocatalysts and certain metal-doped electrocatalysts.

https://onlinelibrary.wiley.com/doi/epdf/10.1002/advs.201700515

Recent Progress on MOF‐Derived Heteroatom‐Doped Carbon‐Based Electrocatalysts for Oxygen Reduction Reaction

Porous Fe-Nx/C hybrid derived from bi-metal organic frameworks as high efficient electrocatalyst for oxygen reduction reaction

A single-crystalline native dielectric for two-dimensional semiconductors with an equivalent oxide thickness below 0.5 nm

High-mobility and air-stable two-dimensional (2D) Bi2O2Se semiconductor holds promise as an alternative fast channel material for next-generation transistors. However, one of the key challenges remaining in 2D Bi2O2Se is to prepare high-quality crystals to fabricate the high-performance transistors with a high on-state current density. Here, we present the free-standing growth of strain-free 2D Bi2O2Se crystals. An ultrahigh Hall mobility of 160 000 cm2 V-1 s-1 is measured in strain-free Bi2O2Se crystals at 2 K, which enables the observation of Shubnikov-de Haas quantum oscillations and shows substantially higher (>4 times) mobility over previous in-plane 2D crystals. The fabricated 2D transistors feature an on-off current ratio of ∼106 and a record-high on-state current density of ∼1.33 mA μm-1, which is comparable to that of commercial Si and Ge n-type field-effect transistors (FETs) for similar channel length. Strain-free 2D Bi2O2Se provides a promising material platform for studying novel quantum phenomena and exploration of high-performance low-power electronics.

Strain-Free Layered Semiconductors for 2D Transistors with On-State Current Density Exceeding 1.3 mA μm-1.

Significance Interaction of charge carriers with phonons is an intrinsic property of semiconductors and has been commonly treated as a perturbation in the harmonic approximation to the quasi-particle band picture. Recent discoveries in lead halide perovskites have challenged this traditional view, suggested efficient charge screening by dynamically disordered and anharmonic phonons, and cultivated the proposal of ferroelectric polaron formation as one of the keys to the success of these materials. The present study provides experimental and theoretical evidence for the ferroelectric polaron in Bi2O2Se and serves as a first step toward generalizing this principle for the discovery of defect-tolerant semiconductors in optoelectronics applications.

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Tengxiu Tu

Papers

Porous Fe-Nx/C hybrid derived from bi-metal organic frameworks as high efficient electrocatalyst for oxygen reduction reaction

A single-crystalline native dielectric for two-dimensional semiconductors with an equivalent oxide thickness below 0.5 nm

Strain-Free Layered Semiconductors for 2D Transistors with On-State Current Density Exceeding 1.3 mA μm-1.

Phonon signatures for polaron formation in an anharmonic semiconductor

Single-crystalline van der Waals layered dielectric with high dielectric constant