Highly Efficient Water Oxidation Photoanode Made of Surface Modified LaTiO₂ N Particles

An improved variation of highly active/durable O₂ -evolving LaTiO₂ N powder-based photoelectrode has been fabricated by pre-cleaning the powder with mild polysulfonic acid and by homogeneous deposition of CoO_x co-catalyst aided by microwave annealing. The treatment in aqueous solution of poly(4-styrene sulfonic acid) results in removal of surface LaTiO₂ N layers, forming fine pores in the crystallites. The CoO_x co-catalyst by microwave deposition in Co(NH₃ )₆ Cl₃ /ethylene glycol homogeneously covers the particle surface. The LaTiO₂ N powder is fabricated into particle-transferred electrodes on Ti thin film supported on solid substrate. The modified LaTiO₂ N grains on the electrode serve as a highly active O₂ -evolving photoanode achieving 8.9 mA cm^-2 of the photocurrent density at 1.23 V versus reversible hydrogen electrode (RHE) in 0.1 m NaOH (pH 13) under solar-simulator irradiation Airmass 1.5 Global (AM 1.5G). The activity has been much improved, compared with conventional LaTiO₂ N treated in mineral acid or with CoO_x deposited by impregnation. The new electrode also exhibits better durability in fixed-potential chronoamperometric tests under AM 1.5G irradiation.