Solar water splitting for hydrogen production with monolithic reactors

The present work proposes the exploitation of solar energy for the dissociation of water and production of hydrogen via an integrated thermo-chemical reactor/receiver system. The basic idea is the use of multi-channelled honeycomb ceramic supports coated with active redox reagent powders, in a configuration similar to that encountered in automobile exhaust catalytic aftertreatment. Iron-oxide-based redox materials were synthesized, capable to operate under a complete redox cycle: they could take oxygen from water producing pure hydrogen at reasonably low temperatures (800 degrees C) and could be regenerated at temperatures below 1300 degrees C. Ceramic honeycombs capable of achieving temperatures in that range when heated by concentrated solar radiation were manufactured and incorporated in a dedicated solar receiver/reactor. The operating conditions of the solar reactor were optimised to achieve adjustable, uniform temperatures up to 1300 degrees C throughout the honeycomb, making thus feasible the operation of the complete cycle by a single solar energy converter. (c) 2005 Elsevier Ltd. All rights reserved.