Self-Limiting Growth of Single-Layer N-Doped Graphene Encapsulating Nickel Nanoparticles for Efficient Hydrogen Production

Magnesium: properties and rich chemistry for new material synthesis and energy applications

Magnesium (Mg) has many unique properties suitable for applications in the fields of energy conversion and storage. These fields presently rely on noble metals for efficient performance. However, among other challenges, noble metals have low natural abundance, which undermines their sustainability. Mg has a high negative standard reduction potential and a unique crystal structure, and its low melting point at 650 °C makes it a good candidate to replace or supplement numerous other metals in various energy applications. These attractive features are particularly helpful for improving the properties and limits of materials in energy systems. However, knowledge of Mg and its practical uses is still limited, despite recent studies which have reported Mg's key roles in synthesizing new structures and modifying the chemical properties of materials. At present, information about Mg chemistry has been rather scattered without any organized report. The present review highlights the chemistry of Mg and its uses in energy applications such as electrocatalysis, photocatalysis, and secondary batteries, among others. Future perspectives on the development of Mg-based materials are further discussed to identify the challenges that need to be addressed.

Dual interfacial engineering of a Chevrel phase electrode material for stable hydrogen evolution at 2500 mA cm-2

Constructing stable electrodes which function over long timescales at large current density is essential for the industrial realization and implementation of water electrolysis. However, rapid gas bubble detachment at large current density usually results in peeling-off of electrocatalysts and performance degradation, especially for long term operations. Here we construct a mechanically-stable, all-metal, and highly active CuMo₆S₈/Cu electrode by in-situ reaction between MoS₂ and Cu. The Chevrel phase electrode exhibits strong binding at the electrocatalyst-support interface with weak adhesion at electrocatalyst-bubble interface, in addition to fast hydrogen evolution and charge transfer kinetics. These features facilitate the achievement of large current density of 2500 mA cm⁻² at a small overpotential of 334 mV which operate stably at 2500 mA cm⁻² for over 100 h. In-situ total internal reflection imaging at micrometer level and mechanical tests disclose the relationships of two interfacial forces and performance of electrocatalysts. This dual interfacial engineering strategy can be extended to construct stable and high-performance electrodes for other gas-involving reactions.

Stable electrodes which operate at large current density are essential for industrial water electrolysis. Here, a highly active Chevrel phase electrode is reported to achieve 2500 mA/cm⁻² current density for 300 hours at small overpotentials.

Self-Templated Formation of Fluffy Graphene-Wrapped Ni5P4 Hollow Spheres for Li-Ion Battery Anodes with High Cycling Stability

Transition-metal phosphides have gained great importance in the field of energy conversion and storage such as electrochemical water splitting, fuel cells, and Li-ion batteries. In this study, a rationally designed novel fluffy graphene (FG)-wrapped monophasic Ni₅P₄ (Ni₅P₄@FG) is in-situ-synthesized using a chemical vapor deposition method as a Li-ion battery anode material. The porous and hollow structure of Ni₅P₄ core is greatly helpful for lithium-ion diffusion, and at the same time, the cilia-like graphene nanosheet shell provides an electron-conducting layer and stabilizes the solid electrolyte interface formed on the Ni₅P₄ surface. The Ni₅P₄@FG sample shows a high reversible capacity of 739 mAh g^-1 after 300 cycles at a specific current density of 500 mA g^-1. The high capacity, superior cycling stability, and improved rate capability of Ni₅P₄@FG are ascribed to its unique hierarchical structure. Moreover, the present efficient fabrication methodology of Ni₅P₄@FG has potential to be developed as a general method for the synthesis of other transition-metal phosphides.