Combined nanostructured Bi2S3/TNA photoanode and Pt/SiPVC photocathode for efficient self-biasing photoelectrochemical hydrogen and electricity generation

Abstract

A good visible light responsive nanostructured Bi2S3/TiO2 nanotube array (TNA) photoanode has been prepared for efficient self-biasing photoelectrochemical (PEC) hydrogen and electricity generation by combining with a Pt/SiPVC photocathode based on the mismatching Fermi levels between photoelectrodes. Under visible-light irradiation, the potential of Bi2S3/TNA photoanode is more negative than that of Pt/SiPVC photocathode, leading to a self-bias (open-circuit voltage Voc=0.766V) which can facilitate photogenerated electrons in Bi2S3/TNA to recombine with photogenerated holes in Pt/SiPVC via external circuit. Intensity modulated photocurrent spectroscopy (IMPS) measurements showed that the transit time (τd) was 8.54ms for photogenerated electrons in Bi2S3/TNA photoanode and 6.42ms for photogenerated holes in Pt/SiPVC photocathode, both of which were less than that of traditional PEC cells made up of Bi2S3/TNA photoanode and Pt counter-electrode (Bi2S3/TNA–Pt, 22.27ms) or Pt/SiPVC photocathode and Pt counter-electrode (Pt–Pt/SiPVC, 15.85ms). This demonstrates an efficient charge transport and low electron–hole recombination rate in the self-biasing PEC cell. In this system, short-circuit current, fill factor, and photoelectric conversion efficiency was 1.55mAcm−2, 0.602, and 0.718%, respectively. A H2 evolution rate of ~45.5µmolcm−2h−1, which was 141 times larger than Bi2S3/TNA–Pt and 1.8 times larger than Pt–Pt/SiPVC, was also achieved.