Electrolyte-less design of PEC cells for solar fuels: Prospects and open issues in the development of cells and related catalytic electrodes

The possibilities and prospects offered from a new electrolyte-less (EL) cell design for photoelectro catalytic (PEC) cells to produce solar fuels, particularly by reduction of CO2, are discussed in this perspective contribution. The concept of EL configuration is presented evidencing the several potential advantages, but also the need to develop novel specific nanostructured electrodes. Some aspects of the preparation of photoanode and electrocatalysts for EL-PEC solar cells are discussed, with focus on thin films based on arrays of vertically aligned TiO2 nanotubes and nanocarbon-based gas diffusion catalytic electrodes for CO2 reduction, respectively. New possibilities for design of cells, particularly suitable for medium-high temperature of operations (150-200 degrees C), necessary for process intensification and reduction of the costs, are also presented. These new type of cells require the development of new types of semiconductors, which are briefly outlined. (C) 2015 Elsevier B.V. All rights reserved.