Transition metal nitrides (TMNs), by virtue of their unique electronic structure, high electrical conductivity, superior chemical stability, and excellent mechanical robustness, have triggered tremendous research interest over the past decade, and showed great potential for electrochemical energy conversion and storage. However, bulk TMNs usually suffer from limited numbers of active sites and sluggish ionic kinetics, and eventually ordinary electrochemical performance. Designing nanostructured TMNs with tailored morphology and good dispersity has proved an effective strategy to address these issues, which provides a larger specific surface area, more abundant active sites, and shorter ion and mass transport distances over the bulk counterparts. Herein, the most up-to-date progress on TMN-based nanomaterials is comprehensively reviewed, focusing on geometric-structure design, electronic-structure engineering, and applications in electrochemical energy conversion and storage, including electrocatalysis, supercapacitors, and rechargeable batteries. Finally, we outline the future challenges of TMN-based nanomaterials and their possible research directions beyond electrochemical energy applications.

Transition metal nitrides for electrochemical energy applications.

Lithium–sulfur batteries (Li–S) have become a viable alternative to future energy storage devices. The electrochemical reaction based on lithium and sulfur promises an extraordinary theoretical energy density, which is far higher than current commercialized Li-ion batteries. However, the principal disadvantage impeding the success of Li–S batteries lies in the severe leakage and migration of soluble lithium polysulfide intermediates out of cathodes upon cycling. The loss of active sulfur species incurs significant capacity decay and poor battery lifespans. Considerable efforts have been devoted to developing various sulfur host materials that can effectively anchor lithium polysulfides. Herein, a comprehensive review is presented of recent advances in sulfur host materials. On the basis of the electrochemistry of Li–S batteries, the strategies for anchoring polysulfides are systematically categorized into physical confinement and chemical bonding. The structural merits of various sulfur host materials are highlighted, and the interaction mechanisms with sulfur species are discussed in detail, which provides valuable insights into the rational design and engineering of advanced sulfur host materials facilitating the commercialization of Li–S batteries. Future challenges and promising research prospects for sulfur host materials are proposed at the end of the review.

Host Materials Anchoring Polysulfides in Li–S Batteries Reviewed

Colloidal carbon sphere nanoreactors have been explored extensively as a class of versatile materials for various applications in energy storage, electrochemical conversion, and catalysis, due to their unique properties such as excellent electrical conductivity, high specific surface area, controlled porosity and permeability, and surface functionality. Here, the latest updated research on colloidal carbon sphere nanoreactor, in terms of both their synthesis and applications, is summarized. Various synthetic strategies are first discussed, including the hard template method, the soft template method, hydrothermal carbonization, the microemulsion polymerization method, and extension of the Stober method. Then, the functionalization of colloidal carbon sphere nanoreactors, including the nanoengineering of compositions and the surface features, is discussed. Afterward, recent progress in the major applications of colloidal carbon sphere nanoreactors, in the areas of energy storage, electrochemical conversion, and catalysis, is presented. Finally, the perspectives and challenges for future developments are discussed in terms of controlled synthesis and functionalization of the colloidal carbon sphere nanoreactors with tunable structure, and the composition and properties that are desirable for practical applications.

Nanoengineering Carbon Spheres as Nanoreactors for Sustainable Energy Applications

Geopolymer for use in heavy metals adsorption, and advanced oxidative processes: A critical review

Lithium-sulfur (Li-S) batteries have a high specific energy capacity and density of 1675 mAh g-1 and 2670 Wh kg-1 , respectively, rendering them among the most promising successors for lithium-ion batteries. However, there are myriads of obstacles in the practical application and commercialization of Li-S batteries, including the low conductivity of sulfur and its discharge products (Li2 S/Li2 S2 ), volume expansion of sulfur electrode, and the polysulfide shuttle effect. Hence, immense attention has been devoted to rectifying these issues, of which the application of metal-based compounds (i.e., transition metal, metal phosphides, sulfides, oxides, carbides, nitrides, phosphosulfides, MXenes, hydroxides, and metal-organic frameworks) as sulfur hosts is profiled as a fascinating strategy to hinder the polysulfide shuttle effect stemming from the polar-polar interactions between the metal compounds and polysulfides. This review encompasses the fundamental electrochemical principles of Li-S batteries and insights into the interactions between the metal-based compounds and the polysulfides, with emphasis on the intimate structure-activity relationship corroborated with theoretical calculations. Additionally, the integration of conductive carbon-based materials to ameliorate the existing adsorptive abilities of the metal-based compound is systematically discussed. Lastly, the challenges and prospects toward the smart design of catalysts for the future development of practical Li-S batteries are presented.

Lithium–Sulfur Battery Cathode Design: Tailoring Metal-Based Nanostructures for Robust Polysulfide Adsorption and Catalytic Conversion

Recent Advances in Transition Metal Nitride-Based Materials for Photocatalytic Applications

Ordered Mesoporous Cobalt–Nickel Nitride Prepared by Nanocasting for Oxygen Evolution Reaction Electrocatalysis

As sustainable energy becomes a major concern for modern society, renewable and clean energy systems need highly active, stable, and low-cost catalysts for the oxygen evolution reaction (OER). Mesoporous materials offer an attractive route for generating efficient electrocatalysts with high mass transport capabilities. Herein, we report an efficient hard templating pathway to design and synthesize three-dimensional (3-D) mesoporous ternary nickel iron nitride (Ni3FeN). The as-synthesized electrocatalyst shows good OER performance in an alkaline solution with low overpotential (259 mV) and a small Tafel slope (54 mV dec−1), giving superior performance to IrO2 and RuO2 catalysts. The highly active contact area, the hierarchical porosity, and the synergistic effect of bimetal atoms contributed to the improved electrocatalytic performance toward OER. In a practical rechargeable Zn–air battery, mesoporous Ni3FeN is also shown to deliver a lower charging voltage and longer lifetime than RuO2. This work opens up a new promising approach to synthesize active OER electrocatalysts for energy-related devices.

https://link.springer.com/content/pdf/10.1007/s40820-020-0412-8.pdf

Mesoporous Ternary Nitrides of Earth-Abundant Metals as Oxygen Evolution Electrocatalyst.

Metal-support interaction strongly influences the catalytic properties of metal-based catalysts Here, titanium nitride (TiN) nanospheres are shown to be an outstanding support, for tuning the electronic property of platinum (Pt) nanoparticles and adjusting the morphology of indium sulfide (In2S3) active components, forming flower-like core-shell nanostructures (TiN-Pt@In2S3) The strong metal-support interaction between Pt and TiN through the formation of Pt-Ti bonds favors the migration of charge carriers and leads to the easy reducibility of TiN-Pt, thus improving the photocatalytic atom efficiency of Pt The TiN-Pt@In2S3 composite shows reduction of Pt loading by 70% compared to the optimal Pt-based system In addition, the optimal TiN-Pt@In2S3 composite exhibits a H2 evolution rate 4 times that of a Pt reference This increase outperforms all other supports reported thus far

Siqi Liu

Papers

Recent Advances in Transition Metal Nitride-Based Materials for Photocatalytic Applications

Ordered Mesoporous Cobalt–Nickel Nitride Prepared by Nanocasting for Oxygen Evolution Reaction Electrocatalysis

Mesoporous Ternary Nitrides of Earth-Abundant Metals as Oxygen Evolution Electrocatalyst.

Titanium Nitride-Supported Platinum with Metal-Support Interaction for Boosting Photocatalytic H2 Evolution of Indium Sulfide.

Prussian blue derived Fe2N for efficiently improving the photocatalytic hydrogen evolution activity of g-C3N4 nanosheets