Sb₂S₃/TiO₂ Heterojunction Photocathodes: Band Alignment and Water Splitting Properties

Abstract

Antimony sulfide (Sb2S3) is a promising light absorbing semiconductor for photovoltaic applications, though it remains vastly unexplored for photoelectrochemical water splitting. Sb2S3 was synthesized by a simple sulfurization of electrodeposited antimony metal at relatively low temperatures (240-300°C) with elemental sulfur. Using a TiO2 buffer layer and a platinum cocatalyst, photocurrent densities up to ~ 9 mA cm-2 were achieved at-0.4 V vs. RHE in 1 M H2SO4 under one sun illumination. Using XPS band alignment studies and potential dependent IPCE measurements, a conduction band offset of 0.7 eV was obtained for the Sb2S3/TiO2 junction as well as an unfavorable band bending at the heterointerface, which explains the low photovoltage that was observed (~ 0.1 V). Upon inserting an In2S3 buffer layer, which offers a better band alignment, a 0.15 V increase in photovoltage was obtained. The excellent PEC performance and the identification of the origin of the low photovoltage of the Sb2S3 photocathodes in this work pave the way for the further development of this promising earth abundant light absorbing semiconductor for solar fuels generation.

Natural Band Alignments and Band Offsets of Sb2Se3 Solar Cells

“…This suggests that there is a large degree of charge transfer upon contact, which increases the VBO (and CBO) from the natural value. The existence of a clifflike offset is supported by the observation of a similar alignment for Sb 2 S 3 and TiO 2 reported elsewhere …”

Heterojunction interface engineering enabling high onset potential in Sb2Se3/CdS photocathodes for efficient solar hydrogen production

“…To achieve a high STH conversion efficiency, the light absorbing photoelectrode materials should be capable of absorbing sufficient sunlight, transporting to the electrolyte efficiently, and remaining long-term stable without photocorrosion [4] . To date, numerous semiconductors have been developed for PEC solar hydrogen production, such as Si [5] , SiC [6] , Cu 2 O [7] , CdTe [8] , Cu-chalcogenides [9][10][11][12] and Sb-chalcogenides [13,14] . However, the continuous exploration of earth-abundant and low-cost candidates are still getting growing concerns.…”

Heterostructure-Induced Light Absorption and Charge-Transfer Optimization of a TiO2 Photoanode for Photoelectrochemical Water Splitting

“…Zheng et al grew narrow band gap ZnFe 2 O 4 leaves on TiO 2 trees by atomic layer deposition and a boosted PEC water splitting ability was also achieved. With regard to electron–hole separation, heterostructure construction is an efficient approach. − It was demonstrated that a facet heterojunction structure between rutile TiO 2 nanorods and different facets of TiO 2 nanosheets can promote charge transfer and prolong the lifetime of photogenerated electrons . Prabhakar et al also reported that Sb 2 S 3 /TiO 2 heterojunction photocathodes could achieve a high photocurrent density with good band alignment .…”

“…With regard to electron–hole separation, heterostructure construction is an efficient approach. − It was demonstrated that a facet heterojunction structure between rutile TiO 2 nanorods and different facets of TiO 2 nanosheets can promote charge transfer and prolong the lifetime of photogenerated electrons . Prabhakar et al also reported that Sb 2 S 3 /TiO 2 heterojunction photocathodes could achieve a high photocurrent density with good band alignment . Therefore, modification of TiO 2 with a narrow band gap semiconductor to construct a heterostructure would be promising to extend the light absorption range and facilitate charge separation for improving the PEC water splitting performance.…”

“…23 Prabhakar et al also reported that Sb 2 S 3 /TiO 2 heterojunction photocathodes could achieve a high photocurrent density with good band alignment. 24 Therefore, modification of TiO 2 with a narrow band gap semiconductor to construct a heterostructure would be promising to extend the light absorption range and facilitate charge separation for improving the PEC water splitting performance.…”