Search

Oxide perovskites have emerged as an important class of materials with important applications in many technological areas, particularly thermocatalysis, electrocatalysis, photocatalysis, and energy storage. However, their implementation faces numerous challenges that are familiar to the chemist and materials scientist. The present work surveys the state-of-the-art by integrating these two viewpoints, focusing on the critical role that defect engineering plays in the design, fabrication, modification, and application of these materials. An extensive review of experimental and simulation studies of the synthesis and performance of oxide perovskites and devices containing these materials is coupled with exposition of the fundamental and applied aspects of defect equilibria. The aim of this approach is to elucidate how these issues can be integrated in order to shed light on the interpretation of the data and what trajectories are suggested by them. This critical examination has revealed a number of areas in which the review can provide a greater understanding. These include considerations of (1) the nature and formation of solid solutions, (2) site filling and stoichiometry, (3) the rationale for the design of defective oxide perovskites, and (4) the complex mechanisms of charge compensation and charge transfer. The review concludes with some proposed strategies to address the challenges in the future development of oxide perovskites and their applications.

Template-directing strategies for synthesising metal-organic frameworks (MOFs) have brought about new frontiers in materials chemistry due to the possibility of applying control over crystal growth, morphology and secondarily generated pores. In particular, hard templates have resulted in performance breakthroughs in catalysis, secondary ion batteries, supercapacitance, drug delivery and molecular sieving by offering facile routes for maximising the surface areas of shape-directed MOFs. In this tutorial review, a variety of hard templates employed to direct MOFs' growth into superior nano-architectures with enhanced functionalities are discussed. Hard templates discussed here include polymers, silica nanostructures, metal oxides, layered metal hydroxides, noble metals, graphene, zeolites and MOFs themselves. These templates can be divided into three broad categories: sacrificial, semi-sacrificial and non-sacrificial templates. We elaborate on the rationale behind the choice of nanomaterials as hard templates, how hard templates direct the synthesis of MOFs, how sacrificial hard templates can be removed from the final product and what the enhanced functionalities of hard-templated MOFs are. In the case of non-sacrificial hard-templates, synergistic effects arising from the coexistence of the MOF and the hard template will also be reviewed.