  The production of hydrogen from water using only a catalyst and solar energy
is one of the most challenging and promising outlets for the generation of
clean and renewable energy. Semiconductor photocatalysts for solar hydrogen
production by water photolysis must employ stable, non-toxic, abundant and
inexpensive visible-light absorbers capable of harvesting light photons with
adequate potential to reduce water. Here, we show that a-Fe2O3 can meet these
requirements by means of using hydrothermally prepared nanorings. These iron
oxide nanoring photocatalysts proved capable of producing hydrogen efficiently
without application of an external bias. In addition, Co(OH)2 nanoparticles
were shown to be efficient co-catalysts on the nanoring surface by improving
the efficiency of hydrogen generation. Both nanoparticle-coated and uncoated
nanorings displayed superior photocatalytic activity for hydrogen evolution
when compared with TiO2 nanoparticles, showing themselves to be promising
materials for water-splitting using only solar light.
