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

https://espace.library.uq.edu.au/view/UQ:113b151/UQ113b151_OA.pdf

Boosting the cycling stability of transition metal compounds-based supercapacitors

In this study, a general and effective phosphorization strategy is successfully demonstrated to enhance supercapacitor performance of various transition metals oxide or hydroxide, such as Ni(OH)2, Co(OH)2, MnO2, and Fe2O3. For example, a 3D networked Ni2P nanosheets array via a facile phosphorization reaction of Ni(OH)2 nanosheets is grown on the surface of a Ni foam. The Ni foam-supported Ni2P nanosheet (Ni2P NS/NF) electrode shows a remarkable specific capacitance of 2141 F g−1 at a scan rate of 50 mV s−1 and remains as high as 1109 F g−1 even at the current density of 83.3 A g−1. The specific capacitance is much larger than those of Ni(OH)2 NS/NF (747 F g−1 at 50 mV s−1). Furthermore, the electrode retains a high specific capacitance of 1437 F g−1 even after 5000 cycles at a current density of 10 A g−1, in sharp contrast with only 403 F g−1 of Ni(OH)2 NS/NF at the same current density. The similar enhanced performance is observed for Ni2P powder, which eliminates the influence of nickel foam. The enhanced supercapacitor performances are attributed to the 3D porous nanosheets network, enhanced conductivity, and two active components of Ni2+ and Pδ− with rich valences of Ni2P.

Ultrahigh‐Performance Pseudocapacitor Electrodes Based on Transition Metal Phosphide Nanosheets Array via Phosphorization: A General and Effective Approach

Porous carbon electrodes have emerged as important cathode materials for metal-air battery systems. However, most approaches for fabricating porous carbon electrodes from biomass are highly energy inefficient as they require the breaking down of the biomass and its subsequent reconstitution into powder-like carbon. Here, enzymes are explored to effectively hydrolyze the partial cellulose in bulk raw wood to form a large number of nanopores, which helps to maximally expose the inner parts of the raw wood to sufficiently dope nitrogen onto the carbon skeletons during the subsequent pyrolysis process. The resulting carbons exhibit excellent catalytic activity with respect to the oxygen reduction and oxygen evolution reactions. As-fabricated cellulose-digested, carbonized wood plates are mechanically strong, have high conductivity, and contain a crosslinked network and natural ion-transport channels and can be employed directly as metal-free electrodes without carbon paper, polymer binders, or carbon black. When used as metal-free cathodes in zinc-air batteries, they result in a specific capacity of 801 mA h g-1 and an energy density of 955 W h kg-1 with the long-term stability of the batteries being as high as 110 h. This work paves the way for the ready conversion of abundant biomass into high-value engineering products for energy-related applications.

Hierarchically Porous Carbon Plates Derived from Wood as Bifunctional ORR/OER Electrodes.

Recently, asymmetric supercapacitors (ASCs) have attracted extensive research interest worldwide for their potential application in emerging energy-related fields. The smart integration of high overall cell operating voltage and large capacitance can be realized in all-pseudocapacitive-electrode-materials-based ASCs. This innovative all-pseudocapacitive-asymmetric design provides a fascinating way to obtain high-energy-density devices with high power rates and also holds huge potential to bridge the gap between dielectric capacitors and rechargeable batteries. In the present review, we mainly summarized the latest contributions and progress in aqueous/non-aqueous faradaic electrode materials including conductive polymers and/or transition metal oxides/sulfides/nitrides/carbides, the operating principles, system design/engineering, and the rational optimization of all-pseudocapacitive ASCs. The intrinsic advantages and disadvantages of these unique ASCs have been elaborately discussed and comparatively evaluated. Finally, some future trends, prospects, and challenges, especially in rate capability and cycling stability, have been presented for advanced next-generation ASCs.

Recent progresses in high-energy-density all pseudocapacitive-electrode-materials-based asymmetric supercapacitors

Ultrathin MoO3 nanocrystalsself-assembled on graphene nanosheets via oxygen bonding as supercapacitor electrodes of high capacitance and long cycle life

Graphene-supported mesoporous carbons with rich nitrogen self-doped active sites (N-MC/rGO) are prepared by direct pyrolysis of a graphene-oxide-supported polymer composite embedded with massive, evenly distributed amorphous FeOOH that serve as efficient thermally removable templates. The resulting N-MC/rGO catalysts exhibit high surface areas and apparent electrocatalytic activity for oxygen reduction reaction in alkaline media. Among the series, the sample prepared at 800 °C displays the best performance with a more positive onset potential, higher limiting currents, much higher stability, and stronger poison resistance than commercial Pt/C. This is ascribed to the synergetic functions of the highly conductive graphene support and the mesoporous N-doped carbons that effectively impede the restacking of the graphene sheets and enhance the exposure of the rich nitrogen self-doped active sites.

Graphene-Supported Mesoporous Carbons Prepared with Thermally Removable Templates as Efficient Catalysts for Oxygen Electroreduction

One-pot synthesis of graphene/carbon nanospheres/graphene sandwich supported Pt3Ni nanoparticles with enhanced electrocatalytic activity in methanol oxidation

Ruthenium nanoparticles were prepared by thermolytic reduction of RuCl3 in 1,2-propanediol containing sodium 2-naphthalenecarboxylate. Transmission electron microscopic measurements showed that the average diameter of the resulting 2-naphthalenecarboxylate-protected ruthenium nanoparticles (RuCOONA) was 1.30 ± 0.27 nm. Interestingly, hydrothermal treatment of the nanoparticles at controlled temperatures led to decarboxylation at the metal–ligand interface, and the naphthalenyl moieties became directly bonded to the metal cores, which was confirmed by infrared and X-ray photoelectron spectroscopic measurements. In comparison with the as-produced RuCOONA nanoparticles, the decarboxylated nanoparticles (RuNA) exhibited markedly different optical and electronic properties, as manifested by an apparent red shift of the photoluminescence profiles, which was ascribed to electronic coupling between the particle-bound naphthalene groups. Electrochemical measurements exhibited consistent results where a negative sh...

https://chen.chemistry.ucsc.edu/acs.jpcc.5b04312.pdf

Chemical Reactivity of Naphthalenecarboxylate-Protected Ruthenium Nanoparticles: Intraparticle Charge Delocalization Derived from Interfacial Decarboxylation

Wei Li

Papers

Ultrathin MoO3 nanocrystalsself-assembled on graphene nanosheets via oxygen bonding as supercapacitor electrodes of high capacitance and long cycle life

Graphene-Supported Mesoporous Carbons Prepared with Thermally Removable Templates as Efficient Catalysts for Oxygen Electroreduction

One-pot synthesis of graphene/carbon nanospheres/graphene sandwich supported Pt3Ni nanoparticles with enhanced electrocatalytic activity in methanol oxidation

Chemical Reactivity of Naphthalenecarboxylate-Protected Ruthenium Nanoparticles: Intraparticle Charge Delocalization Derived from Interfacial Decarboxylation

High-Performance Supercapacitors Based on Nitrogen-Doped Porous Carbon from Surplus Sludge