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

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 co-catalyst, 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.

Download Full-text

Enhancement of photoelectrochemical performance in ferroelectric films via the introduction of an Au buffer layer

Journal of Semiconductors ◽

10.1088/1674-4926/42/11/112701 ◽

2021 ◽

Vol 42 (11) ◽

pp. 112701

Author(s):

Dawei Cao ◽

Ming Li ◽

Jianfei Zhu ◽

Yanfang He ◽

Tong Chen ◽

...

Keyword(s):

Electric Field ◽

Buffer Layer ◽

Water Splitting ◽

Charge Separation ◽

Sol Gel ◽

Ferroelectric Films ◽

Photoelectrochemical Performance ◽

Band Bending ◽

Polarization Electric Field ◽

Pec Water Splitting

Abstract The inefficient separation of photogenerated carriers has become a serious problem that limits the photoelectrochemical (PEC) performance of semiconductors. Herein, a sol-gel method was used to prepare BiFeO3 ferroelectric thin films with FTO and FTO/Au as substrates, respectively. The polarization electric field of the ferroelectric can more effectively separate the carriers generated in the photoelectrode. Meanwhile, the introduction of an Au buffer layer can reduce the resistance in the process of charge transfer, accelerate the carrier migration, and enhance the efficiency of the charge separation. Under light irradiation, Au/BiFeO3 photoelectrode exhibited an extraordinary improvement in PEC water splitting compared with BiFeO3. In addition, the ferroelectric polarization electric field causes band bending, which further accelerates the separation of electrons and holes and improves the PEC performance of the photoelectrode. This work promotes the effective application of ferroelectric films in PEC water splitting.

Download Full-text

A Rapid Solar Reduction Method to TiO2/MoO2/Graphene Nanocomposites for Photocatalytic Water Splitting

MRS Proceedings ◽

10.1557/opl.2015.296 ◽

2015 ◽

Vol 1738 ◽

Author(s):

Jyothirmayee Aravind.S.S ◽

Kandalam Ramanujachary ◽

Timothy D. Vaden ◽

Amos Mugweru

Keyword(s):

Water Splitting ◽

Reduction Method ◽

High Current Density ◽

Phase Identification ◽

Co Catalyst ◽

Graphene Nanocomposites ◽

Photocatalytic Water Splitting ◽

Earth Abundant ◽

Co Reduction ◽

Interesting Area

ABSTRACTSemiconductor photocatalysis has emerged as an interesting area of research since the discovery of Honda-Fujishima effect. In this study, TiO2/MoO2/graphene composites have been prepared by a solar radiation-assisted co-reduction method, wherein ammonium tetrathiomolybdate salt and graphite oxide are reduced to MoO2 and graphene respectively along with TiO2. The method involved the utilization of focused pulses of natural sunlight using a simple convex lens, thereby eliminating the need for harmful reducing agents. The compound was characterized by XRD and SEM for phase identification and morphology. The TiO2/MoO2/graphene composite exhibits superior photocatalytic water splitting activity without using a co-catalyst. In addition, we demonstrate the electrocatalytic hydrogen production using this earth abundant catalyst, which shows high current density (60 mA/cm2) and low Tafel slope (47 mV/dec). The hydrogen evolved during photocatalysis was detected by gas chromatography.

Download Full-text

Inherent Buffer-layer Formation on Chalcopyrite Absorbers

MRS Proceedings ◽

10.1557/proc-1210-q06-08 ◽

2009 ◽

Vol 1210 ◽

Author(s):

Christian Pettenkofer ◽

Andreas Hofmann ◽

Carsten Lehmann ◽

Alexandra Dombrowa

Keyword(s):

Buffer Layer ◽

Photoelectron Spectroscopy ◽

Band Alignment ◽

Initial Growth ◽

Layer Formation ◽

Low Energy Electron Diffraction ◽

Photovoltaic Applications ◽

Step Growth ◽

Low Energy Electron ◽

Excess Sulfur

AbstractWe report on epitaxial growth of ZnO on polycrystalline and (112) orientated CuInS2 and CuInSe2 thin films. Step-by-step growth and investigation by photoelectron spectroscopy (PES) and low energy electron diffraction (LEED) provided information on the growth mode and the electronic structure of the ZnO-CuInS2-interface. During the initial growth no ZnO is deposited. Instead a monolayer of ZnS is formed by depletion the CuInS2 surface of excess sulfur. Thereafter, the ZnO growth starts on the ZnS buffer layer. The band alignment derived from PES shows that the ZnS buffer layer is thin enough to provide a beneficial band alignment for photovoltaic applications. CuInSe2 (112) samples showed a similar behaviour, but at the chosen deposition temperature of 450°C only ZnSe growth is detected. At lower temperatures ZnO growth on top of ZnSe is observed. XPEEM experiments show an inhomogeneous interface.

Download Full-text

Unraveling the synergy between metal–organic frameworks and co-catalysts in photocatalytic water splitting

Journal of Materials Chemistry A ◽

10.1039/d0ta06028c ◽

2020 ◽

Vol 8 (39) ◽

pp. 20493-20502

Author(s):

Stefano Falletta ◽

Patrick Gono ◽

Zhendong Guo ◽

Stavroula Kampouri ◽

Kyriakos C. Stylianou ◽

...

Keyword(s):

Water Splitting ◽

Photocatalytic Performance ◽

Metal Organic Frameworks ◽

Water Systems ◽

Band Alignment ◽

Co Catalyst ◽

Photocatalytic Water Splitting ◽

Co Catalysts ◽

Metal Organic

Theoretical methodologies for the band alignment at MOF/co-catalyst/water systems revealing the electronic and atomistic mechanisms underlying their photocatalytic performance.

Download Full-text

Band alignment investigations of heterostructure NiO/TiO2 nanomaterials used as efficient heterojunction earth-abundant metal oxide photocatalysts for hydrogen production

Physical Chemistry Chemical Physics ◽

10.1039/c7cp01300k ◽

2017 ◽

Vol 19 (29) ◽

pp. 19279-19288 ◽

Cited By ~ 52

Author(s):

Md. T. Uddin ◽

Y. Nicolas ◽

C. Olivier ◽

W. Jaegermann ◽

N. Rockstroh ◽

...

Keyword(s):

Hydrogen Production ◽

Metal Oxide ◽

Band Alignment ◽

Band Bending ◽

Earth Abundant ◽

Tio2 Nanomaterials

Earth-abundant NiO/TiO2 heterostructures lead to enhanced H2 production by methanol photoreforming due to favorable band bending at the interface of the NiO/anatase TiO2 p–n heterojunction.

Download Full-text

Energy band alignment at the heterointerface between CdS and Ag-alloyed CZTS

Scientific Reports ◽

10.1038/s41598-020-73828-0 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Mungunshagai Gansukh ◽

Zheshen Li ◽

Moises Espindola Rodriguez ◽

Sara Engberg ◽

Filipe Mesquita Alves Martinho ◽

...

Keyword(s):

Photoelectron Spectroscopy ◽

Energy Band ◽

Depth Profiling ◽

Band Alignment ◽

Nanometer Scale ◽

Significant Shift ◽

Total Charge ◽

Band Bending ◽

Conduction Band Offset ◽

Depletion Width

Abstract Energy band alignment at the heterointerface between CdS and kesterite Cu2ZnSnS4 (CZTS) and its alloys plays a crucial role in determining the efficiency of the solar cells. Whereas Ag alloying of CZTS has been shown to reduce anti-site defects in the bulk and thus rise the efficiency, the electronic properties at the interface with the CdS buffer layer have not been extensively investigated. In this work, we present a detailed study on the band alignment between n-CdS and p-CZTS upon Ag alloying by depth-profiling ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS). Our findings indicate that core-level peaks and the valence band edge of CdS exhibit a significant shift to a lower energy (larger than 0.4 eV) upon the etching of the CdS layer, which can be assigned due to band bending and chemical shift induced by a change in the chemical composition across the interface. Using a simplified model based on charge depletion layer conservation, a significantly larger total charge region depletion width was determined in Ag-alloyed CZTS as compared to its undoped counterpart. Our findings reveal a cliff-like band alignment at both CdS/CZTS and CdS/Ag-CZTS heterointerfaces. However, the conduction-band offset decreases by more than 0.1 eV upon Ag alloying of CZTS. The approach demonstrated here enables nanometer-scale depth profiling of the electronic structure of the p–n junction and can be universally applied to study entirely new platforms of oxide/chalcogenide heterostructures for next-generation optoelectronic devices.

Download Full-text

Measurements of the Band Offset of SiO2 on Clean GaN

MRS Proceedings ◽

10.1557/proc-693-i9.10.1 ◽

2001 ◽

Vol 693 ◽

Author(s):

E.H. Hurt ◽

Ted E. Cook ◽

K.M. Tracy ◽

R.F. Davis ◽

G. Lucovsky ◽

...

Keyword(s):

Molecular Beam ◽

Electronic States ◽

Band Alignment ◽

Gate Insulator ◽

Band Offset ◽

Valence Band Offset ◽

Band Bending ◽

Analysis Techniques ◽

Conduction Band Offset ◽

Surface Analysis Techniques

AbstractThe band alignment of SiO2 and GaN is important for passivation of high voltage devices and for gate insulator applications. In this study XPS and UPS techniques are employed to determine the electronic states as SiO2 is deposited onto a clean GaN surface. The substrate was epitaxially grown n-type GaN on 6H-SiC (0001) substrates with an AlN (0001) buffer layer. The GaN surface was atomically cleaned via a 860°C anneal in an NH3 atmosphere. For the clean GaN surface, upward band bending of ~0.3 ±0.1 eV was measured, and the electron affinity was measured to be ~2.9 eV. Layers of Si were deposited on the GaN surface via Molecular Beam Epitaxy (MBE), and the Si was oxidized by a remote O2 plasma. The oxidation of the Si occurred without oxidizing the GaN. Densification of the created SiO2 film was achieved by annealing the substrate at 650°C. Surface analysis techniques were performed after each process, and yielded a valence band offset of ~2.0 eV, and a conduction band offset of ~3.6 eV for the GaN-SiO2 interface.

Download Full-text

Sulfur defects rich Mo-Ni3S2 QDs assisted by O-C=O chemical bonding for efficient electrocatalytic overall water splitting

Nanoscale ◽

10.1039/d1nr00605c ◽

2021 ◽

Author(s):

Honglei Chen ◽

Zebin Yu ◽

Ronghua Jiang ◽

Jun Huang ◽

Yanping Hou ◽

...

Keyword(s):

Water Splitting ◽

Chemical Bonding ◽

Highly Efficient ◽

Overall Water Splitting ◽

Earth Abundant ◽

Further Development

Developing earth-abundant and highly efficient electrocatalysts is critical for further development of system. The metal (M) doping strategy and inorganic / organic composite are two common strategies to improve the...

Download Full-text