Semiconductor-mediated heterogeneous photocatalysis is a promising technology for water purifications without generating harmful by-products. The photocatalyst with designed physicochemical properties is the key in the process. Utilization of particulate photocatalysts will create some technological problems, such as difficulty in recycling and management. Thus, cost-effective methods for mass production of highly active photocatalysts that can be operated in an industrial photoreactor with less energy consumption and harmless subsequent consequences are increasingly attracting research attention. Photocatalysts with controllable morphologies at a wide range of scales shall be taken into account in designing the photocatalyst. This review article features recent research progress towards the design and preparation of porous photocatalysts with prescribed structural, compositional, and morphological properties suitable for use in a photocatalytic reactor for water treatment via advanced oxidation processes. With a brief introduction of the important features of a porous photocatalyst in industrial reactors, the review highlights various synthetic strategies for fabricating porous photocatalysts with well-defined microscopic morphologies and nano/meso-scopic active nanobuilding blocks. The synthesis–component–structure–property relationship working in photocatalyst design is discussed. Immobilization of photocatalysts on different porous substrates is highlighted. The perspectives of designing photocatalysts for industrial applications are suggested.

Porous photocatalysts for advanced water purifications

Uniform mesocrystals of TiO2 (anatase) have been prepared from mesocrystals of NH4TiOF3. NH4TiOF3 was synthesized from an aqueous solution containing (NH4)2TiF6 and H3BO3 in the presence of a nonionic surfactant Brij 56, Brij 58, or Brij 700, at low temperatures. The exterior shapes of NH4TiOF3 mesocrystals can be tuned by adjusting the reagent concentration, reaction time, reaction temperature, and rate of stirring. The formation of the NH4TiOF3 mesocrystals proceeds via a self-assembly process involving nonclassical crystal growth. By sintering in air at 450 °C, or washing with H3BO3 solution at ambient temperatures, the NH4TiOF3 mesocrystals can be converted to mesocrystals of TiO2 (anatase), and the original architecture is retained.

A facile synthesis of uniform NH4TiOF3 mesocrystals and their conversion to TiO2 mesocrystals

We demonstrate the feasibility of a nonsalt-based precursor pair—inorganic HPbI3 solid and organic CH3NH2 gas—for the deposition of uniform CH3NH3PbI3 perovskite thin films. The strong room-temperature solid–gas interaction between HPbI3 and CH3NH2 induces transformative evolution of ultrasmooth, full-coverage perovskite thin films at a rapid rate (in seconds) from nominally processed rough, partial-coverage HPbI3 thin films. The chemical origin of this behavior is elucidated via in situ experiments. Perovskite solar cells, fabricated using MAPbI3 thin films thus deposited, deliver power conversion efficiencies up to 18.2%, attesting to the high quality of the perovskite thin films deposited using this transformative process.

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Transformative Evolution of Organolead Triiodide Perovskite Thin Films from Strong Room-Temperature Solid-Gas Interaction between HPbI3-CH3NH2 Precursor Pair.

Structural considerations of intermetallic electrodes for lithium batteries

Structural phase transition-associated dielectric transition and ferroelectricity in coordination compounds

Definitions of phase transitions that relate specifically to the solid state are presented. Various types of transition have been defined; they include: (i) structural transitions of the solid state, (ii) transitions related to the change in the state of matter, i.e., from a solid phase to either a liq. or gaseous phase, or vice-versa, (iii) transitions related to changes in compn., (i.v.) metallurgical transitions, (v) transitions related to changes in the electronic structures of crystals, (vi) transitions that change thermodn. properties or the disorder of a system, and (vii) liq.-crystal transitions. [on SciFinder (R)]

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M. M. Thackeray

Papers

Definitions of terms relating to phase transitions of the solid state