Fabrication of an Efficient BaTaO₂N Photoanode\nHarvesting a Wide Range of Visible Light for Water Splitting

Abstract

Photoanodes made from BaTaO₂N that can harvest visible\nlight up to 660 nm wavelength were fabricated on Ti substrates for\nachieving efficient water splitting. Both pre-treatment of BaTaO₂N particles with an H₂ stream and post-necking\ntreatment with TaCl₅ effectively increased the photocurrent\ndue to the decreased electrical resistance in the porous BaTaO₂N photoanode. A combination of pre-loading of CoO_<i>x</i> on the BaTaO₂N particles and post-loading\nof RhO_<i>x</i> significantly improved both the\nphotocurrent and stability under visible light irradiation, along\nwith an obvious negative shift (ca. 300 mV) of the onset potential\nfor water oxidation, while sole loading resulted in a lower photocurrent\nor insufficient stability. The IPCE value was estimated to be ca.\n10% at 1.2 V vs RHE under 600 nm, which is the highest among photoanode\nmaterials that can harvest light beyond 600 nm for water oxidation.\nPhotoelectrochemical water splitting into H₂ and O₂ under visible light was demonstrated using RhO_<i>x</i>/CoO_<i>x</i>/BaTaO₂N/Ti photoanodes under an externally applied bias larger than 0.7\nV to a Pt counter electrode.