For most of the twentieth century, the chemistry of binary and ternary nitrides progressed very slowly, in marked contrast to the chemistries of metal oxides or fluorides. In major part this slow development can be traced to the limited synthesis routes available, the direct route from the elements is limited by the great strength of the triple bond in dinitrogen which means that only highly thermally stable nitrides can be made by this method. Other routes from nitrogen compounds including ammonia or azides, were limited to specific classes of compound and resulting purities were sometimes poor. The known nitrides were often intractable, inert and difficult to characterise. The last twenty years has seen rapid development of metal nitride chemistry, driven not only by the greatly increased level of effort in solid state and materials chemistry in general, but also by the recognition that nitrides have unique properties which make them very important for some key technological applications.
This themed issue, written by leading experts in the field, brings together articles on several key areas on metal nitride chemistry, including fundamental chemistry and applications in catalysis, photocatalysis, charge storage materials and electronic materials.
The structural chemistry of ternary and higher lithium nitrides across the periodic table is critically discussed by Tapia-Ruiz, Segalés and Gregory, whilst Prior and Francesconi describe how the structure and properties of metal nitrides can be modified by incorporation of other non-metals inclusing O, C, S or halogens.
The chemistry of tris-s-triazines and their use as sources of carbon nitrides is described by Schwarzer, Taplinova and Kroke, who unravel the often confusing literature in this area. Many binary nitrides have low N:M stoichiometries and the article by Salamat, Hector, Kroll and McMillan explores synthesis and structure–property relationships in nitrogen-rich metal nitrides.
The article by Kafizas, Carmalt and Parkin provides a detailed account of the precursor chemistry and chemical vapour deposition of transition metal nitrides, whilst Watson describes the production by metal organic vapour phase epitaxy and the properties, of the nitrides of Al, Ga and In which are industrially important, direct band-gap semiconductors.
Heterogeneous catalysis by metal nitrides is critically evaluated in the article by Hargreaves. The review by Moriya, Takata and Domen discusses the current status of metal nitrides as water splitting photocatalysts, a key step in the development of hydrogen based fuels. The final article by Dong, Chen, Zhang and Cui describes the development of nanostructured metal nitrides as electrode materials for energy storage and conversion.
In summary this themed issue of Coordination Chemistry Reviews presents a state of the art summary of several areas of metal nitride chemistry and demonstrates the important applications of various metal nitrides. It is clear from reading these articles that despite the impressive progress in this area in the last 20 years, much remains to be done both in fundamental studies to prepare currently unknown nitrides and in developing new and existing applications, and thus this volume is a timely summary of the current position.
We thank all the authors for their efforts in contributing to this issue.
