Dicyandiamide-assisted synthesis of N-doped porous CoMn-Nx@N-C carbon nanotube composites via MOFs as efficient trifunctional electrocatalysts in the same electrolyte.

The development of low-cost, long-term stability, and good oxygen reversible catalytic reaction (ORR/OER) and hydrogen evolution (HER) activity under the same electrolyte concentration of electrocatalytic materials has an important role in the construction of large-scale applications and more valuable sustainable energy systems. Among them, the representative CoMn-Nx@N-C-900-0.2 showed good ORR/OER/HER catalytic activity in 0.1 M KOH alkaline electrolyte, specifically manifested by its half-wave potential E = 0.84 V in the ORR test, which was better than that of commercial Pt/C. The total oxygen electrode activity index of OER/ORR was E = 0.79 V, and it also showed good HER performance. When the current density was 10 mA cm-2, the operating potential was E = -0.266 V. The synergistic effects of the CoMn bimetallic alloy, tubular layered porous structure, which exposed more active area and various nitrogen species such as CoMn-Nx, were the main reasons for the improvement of the trifunctional catalytic performance of electrocatalytic materials. The synthesis strategy and analysis of the electrocatalyst performance provide a new reference for the development of multifunctional materials with high catalytic performance.

Organic Cathode Materials for Rechargeable Aluminum-Ion Batteries.

Organic electrode materials (OEMs) have shown enormous potential in ion batteries because of their varied structural components and adaptable construction. As a brand-new energy-storage device, rechargeable aluminum-ion batteries (RAIBs) have also received a lot of attention due to their high safety and low cost. OEMs are expected to stand out among many traditional RAIB cathode materials. However, how to improve the electrochemical performance of OEMs in RAIBs on a laboratory scale is still challenging. This work reviews and discusses the uses of conductive polymers, carbonyl compounds, imine polymers, polycyclic aromatic hydrocarbons, organic frameworks, and other organic materials as the cathodes of RAIBs, as well as energy-storage mechanisms and research progress. It is hoped that this Review can provide the design guidelines for organic cathode materials with high capacity and great stability used in aluminum-organic batteries and develop more efficient organic energy storage cathodes.

Tubular Polypyrrole with Chloride Ion Dopants as an Ultrafast Organic Anode for High-Power Lithium-Ion Batteries.

Polypyrrole (PPy), as a representative p-type conductive polymer, attracts wide attention for energy storage materials. However, the sluggish reaction kinetics and low specific capacity of PPy impede its application in high-power lithium-ion batteries (LIBs). Herein, tubular PPy with chloride and methyl orange (MO) anionic dopants is synthesized and investigated as an anode for LIBs. The Cl- and MO anionic dopants can increase the ordered aggregation and the conjugation length of pyrrolic chains, forming plentiful conductive domains and affecting the conduction channel inside the pyrrolic matrix, thereby achieving fast charge transfer and Li+ ion diffusion, low ion transfer energy barriers, and rapid reaction kinetics. On account of the above synergistic effect, PPy electrodes deliver a high specific capacity of 2067.8 mAh g-1 at 200 mA g-1 and a remarkable rate capacity of 1026 mAh g-1 at 10 A g-1 , realizing high energy density (724 Wh kg-1 ) and power density (7237 W kg-1 ) simultaneously.

Porous MoWN/MoWC@NC Nano-octahedrons synthesized via confined carburization and vapor deposition in MOFs as efficient trifunctional electrocatalysts for oxygen reversible catalysis and hydrogen production in the same electrolyte.

We used a simple MOFs-assisted synthesis strategy based on the encapsulation and in-situ carburizing reaction of Cu-based metallic organic frameworks (NENU-5) to synthesize porous nano-octahedral materials, MoWN/MoWC@NCTs (T = 700, 800, and 900). Together with the vapor deposition strategy, the volatile nitrogen species from the pyrolysis of dicyandiamide were captured by the nano-octahedral materials, and formed tungsten-molybdenum-based carbonitride nanocrystals encapsulated in nitrogen-doped carbon. The porous nano-octahedron has a unique heterostructure composed of Mo2N/MoC/W2N/WC. The representative MoWN/MoWC@NC800 showed trifunctional electrocatalytic activity in oxygen reduction reaction/oxygen evolution reaction/hydrogen evolution reaction (ORR/OER/HER) in an alkaline medium (0.1 M KOH). The total oxygen electrode activity index ΔE = 0.795 V (vs. RHE) was found in OER/ORR, and the material also exhibits excellent HER performance. The minimum potential of -0.17 V (vs. RHE) was provided at a current density of -10 mA cm-2. MoWN/MoWC@NC800 showed excellent cycle stability and durability in ORR/OER/HER with the same electrolyte (0.1 M KOH). More importantly, MoWN/MoWC@NC800 could be used to construct high-performance zinc-air batteries and sued for driving electrocatalytic water splitting in a self-powered manner. The successful preparation of the materials indicate that the synthetic strategy provides new reference ideas for developing functional materials with high catalytic properties for various applications.

Bamboo-like nitrogen-doped porous carbon nanofibers encapsulated nickel-cobalt alloy nanoparticles composite material derived from the electrospun fiber of a bimetal-organic framework as efficient bifunctional oxygen electrocatalysts.

The development of low-cost bifunctional electrocatalysts with both a high activity and long durability is critical for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The reasonable design and construction of bifunctional electrocatalysts is the key to energy storage and energy conversion technologies. In this study, transition metal carbon nitrides were used as a substitute for the precious metal catalyst, the Ni-Co-BTC (metal organic framework (MOF)) mixed with polyacrylonitrile (PAN) using electrostatic spinning technology to prepare the bamboo-like nanofibers precursor (Ni-Co-BTC@PAN). A series of electrocatalytic materials (NiCo-X@N-CNFs-Ts, T = 700, 800, 900 °C) were synthesized with nitrogen-doped carbon nanofibers coated with NiCo alloy nanoparticles using high temperature carbonization at different temperatures. We studied the effects of different calcination temperatures and different Ni/Co molar ratios of NiCo-X@N-CNFs-Ts (T = 700, 800, 900 °C) on the bifunctional catalytic performance of the ORR/OER. The composite, NiCo-0.8@N-CNFs-800, exhibited a highly doped-N level, uniform NiCo alloy nanoparticle dispersion and decentralized NiCo-Nx active sites, therefore affording an excellent bifunctional electrocatalytic performance. The ORR onset potential on NiCo-0.8@N-CNFs-800 was 0.91 V and the half-wave potential (E1/2) was 0.82 V, the NiCo-0.8@N-CNFs-800 corresponded to the minimum potential of 1.61 V at the current density of 10 mA cm-2 among all of the NiCo-X@N-CNFs-Ts hybrids under the OER condition. The NiCo-0.8@N-CNFs-800 catalyst exhibited a low reversible overpotential of 0.79 V between the ORR (E1/2) and OER (Ej = 10 mA cm-2) with excellent stability, durability and methanol tolerance, even surprisingly superior to the commercial Pt/C and RuO2 catalysts. This work provides a general strategy and useful guidance for the design and development of a variety of multifunctional non-noble metal catalysts for energy applications.