Journal
CATALYSIS SCIENCE & TECHNOLOGY
Volume 7, Issue 7, Pages 1602-1610Publisher
ROYAL SOC CHEMISTRY
DOI: 10.1039/c7cy00040e
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Funding
- National Natural Science Foundation of China [51572239, 51372224, 91333203]
- Program for Innovative Research Team in University of Ministry of Education of China [IRT13037]
- National Science and Technology Support Program [2012BAC08B08]
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Cuprous oxide (Cu2O) is expected to be one of the most promising materials for utilizing solar energy. One strategy comprises using Cu2O as a photocathode to obtain hydrogen by the reduction of water. However, the instability of Cu2O in solution hinders its employment to a great extent. Here, we fabricated a multilayer photocathode with the structure of Cu2O/Ga2O3/AZO/TiO2 by the pulsed laser deposition (PLD) technique. The highest photocurrent density was increased to 6.5 mA cm(-2) in comparison to 4.5 mA cm- 2 for bare Cu2O at 0 V versus a reversible hydrogen electrode (RHE), and the stability was also improved to some extent. The properties of Ga2O3 were affected to a great extent by the oxygen pressure, which thereby changed the photovoltage and stability of the photocathode. Alignment of band energies is introduced to explain this phenomenon. In a sample containing Ga2O3 under a low oxygen pressure, the relatively lower Fermi level and conduction band edge in the Ga2O3 layer formed a region of electron accumulation near the interface, which impaired its performance. In addition, the interfacial chemical state of copper element was investigated by X- ray photoelectron spectroscopy (XPS) in combination with Ar ion etching. It was revealed that for both samples Cu+ was reduced to Cu-0 during the fabrication process near the Cu2O/Ga2O3 interface, which is harmful for stability. These factors resulted in the relatively unstable performance of the photocathode. This work reveals the performance of a multilayer photocathode grown by PLD and points out possible ways of improving it.
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