Enhanced solar photocurrent of LaTaON2 photoanodes via electrochemical treatment

Abstract

Having a theoretical 18.5% solar-to-hydrogen efficiency, LaTaON2 has emerged as a promising photoanode material. However, its performance is crucially limited by low photocurrent in the past reports. To improve its solar photocurrent, a negative electrochemical treatment was applied for the LaTaON2 photoanode. The sample powder was successfully synthesized by a flux assisted-nitridation with precursor derived from solid state sintering. And the LaTaON2 photoanodes were fabricated by electrophoretic deposition with a post-necking procedure. The solar photocurrent of as-fabricated LaTaON2 photoanode has increased to 1.2 mA cm-2 at 1.6 VRHE after the negative electrochemical treatment in the dark. The photoanodes with and without the electrochemical treatment were investigated by scanning electron microscopy (SEM), Mott-Schottky test, transient photocurrent and open-circuit photovoltage. The results showed that the enhancement maybe ascribed to the soared carrier density and elimination of surface recombination centre. Therefore it is proposed that the electrochemical treatment eliminates the surface recombination centre of the oxynitrides leading to increased solar photocurrent. It was also found that the SrTaO2N photoanode had increased photocurrent after the electrochemical treatment. This study provides a facile and general way to improve the solar water-splitting current of photoanodes.