Triple-layer ITO/BiVO4/Fe2TiO5 heterojunction photoanode coated with iron silicate for highly efficient solar water splitting

Solar water splitting as a promising way to convert solar energy into hydrogen energy has been largely limited by the low efficiency of photoanodes in photoelectrochemical water oxidation. In this work, through deliberately employing a indium tin oxide (ITO) underlayer as an electron transport layer (ETL) and a Fe 2 TiO 5 overlayer as a hole transport layer (HTL), a novel triple-layer ITO/BiVO 4 /Fe 2 TiO 5 heterojunction photoanode was prepared by solution-processed sequential deposition. Owing to the unique ETL/BiVO 4 /HTL heterojunction structure, the photocurrent density at 1.23 V RHE was significantly increased from 1.70 mA/cm 2 for the pristine BiVO 4 photoanode to 4.60 mA/cm 2 for the ITO/BiVO 4 /Fe 2 TiO 5 photoanode. After iron silicate (Fe-Sil) was deposited as a new and efficient cocatalyst, the resultant quaternary ITO/BiVO 4 /Fe 2 TiO 5 /Fe-Sil photoanode achieved an extremely high photocurrent density of 6.19 mA/cm 2 and an ABPE value as high as 2.55%, indicating an outstanding performance toward solar water oxidation. The high performance of the quaternary ITO/BiVO 4 /Fe 2 TiO 5 /Fe-Sil photoanode may be attributed to the desired ETL/BiVO 4 /HTL heterojunction structure in combination with the utilization of the Fe-Sil as an efficient oxygen evolution cocatalyst.