Silicon Photoanodes for Solar-Driven Oxidation of Brine: A Nanoscale, Photo-Active Analog of the Dimensionally-Stable Anode

Christopher O'Rourke, Robert Tang Kong, Andrew Mills, Paul C. McIntyre

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Abstract

We report the first results in which ALD-TiO2 layers electronically couple silicon to an overlying catalyst coating while inhibiting corrosion during brine splitting, a reaction that is capable of generating not only a fuel (H2) but also a disinfectant (Cl2 or NaOCl). An n-type silicon photoanode, and a p+-silicon anode are protected by a 1.7 nm coating of amorphous TiO2 and 2 nm coating of Ir. The p+-Si/TiO2/Ir anode is able to effect the oxidation of chloride (0.5 M H2SO4, 3.5 M NaCl) in the dark with a low overpotential compared to that for oxidation of water (0.5 M H2SO4). The 0.294 V overpotential difference occurs despite the difference in standard redox potentials, ΔE = (E°(Cl2/Cl−) - E°(O2/H2O)), of 130 mV. Under 1 sun irradiation a photovoltage of ca. 0.566 V is achieved by comparing the illuminated n-Si/TiO2/Ir photoanode with the dark p+-silicon anode. Although the n-Si/TiO2/Ir photoanode is only one half of an eventual tandem cell needed for photosynthetic brine splitting, its ABPE for chloride oxidation is 1.42%, ca. 28 times that for water oxidation. The illuminated n-Si/TiO2/Ir photoanode remained stable at 1 mA cm−2 during a six-day chronopotentiometry test.
Original languageEnglish
Pages (from-to)H1072-H1079
Number of pages8
JournalJournal of the Electrochemical Society
Volume165
Issue number16
DOIs
Publication statusPublished - 29 Dec 2018

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Silicon
Anodes
Oxidation
Coatings
Chlorides
Disinfectants
Water
Sun
Irradiation
Corrosion
Catalysts
brine

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title = "Silicon Photoanodes for Solar-Driven Oxidation of Brine: A Nanoscale, Photo-Active Analog of the Dimensionally-Stable Anode",
abstract = "We report the first results in which ALD-TiO2 layers electronically couple silicon to an overlying catalyst coating while inhibiting corrosion during brine splitting, a reaction that is capable of generating not only a fuel (H2) but also a disinfectant (Cl2 or NaOCl). An n-type silicon photoanode, and a p+-silicon anode are protected by a 1.7 nm coating of amorphous TiO2 and 2 nm coating of Ir. The p+-Si/TiO2/Ir anode is able to effect the oxidation of chloride (0.5 M H2SO4, 3.5 M NaCl) in the dark with a low overpotential compared to that for oxidation of water (0.5 M H2SO4). The 0.294 V overpotential difference occurs despite the difference in standard redox potentials, ΔE = (E°(Cl2/Cl−) - E°(O2/H2O)), of 130 mV. Under 1 sun irradiation a photovoltage of ca. 0.566 V is achieved by comparing the illuminated n-Si/TiO2/Ir photoanode with the dark p+-silicon anode. Although the n-Si/TiO2/Ir photoanode is only one half of an eventual tandem cell needed for photosynthetic brine splitting, its ABPE for chloride oxidation is 1.42{\%}, ca. 28 times that for water oxidation. The illuminated n-Si/TiO2/Ir photoanode remained stable at 1 mA cm−2 during a six-day chronopotentiometry test.",
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Silicon Photoanodes for Solar-Driven Oxidation of Brine: A Nanoscale, Photo-Active Analog of the Dimensionally-Stable Anode. / O'Rourke, Christopher; Tang Kong, Robert; Mills, Andrew; McIntyre, Paul C.

In: Journal of the Electrochemical Society, Vol. 165, No. 16, 29.12.2018, p. H1072-H1079.

Research output: Contribution to journalArticle

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T1 - Silicon Photoanodes for Solar-Driven Oxidation of Brine: A Nanoscale, Photo-Active Analog of the Dimensionally-Stable Anode

AU - O'Rourke, Christopher

AU - Tang Kong, Robert

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AU - McIntyre, Paul C.

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AB - We report the first results in which ALD-TiO2 layers electronically couple silicon to an overlying catalyst coating while inhibiting corrosion during brine splitting, a reaction that is capable of generating not only a fuel (H2) but also a disinfectant (Cl2 or NaOCl). An n-type silicon photoanode, and a p+-silicon anode are protected by a 1.7 nm coating of amorphous TiO2 and 2 nm coating of Ir. The p+-Si/TiO2/Ir anode is able to effect the oxidation of chloride (0.5 M H2SO4, 3.5 M NaCl) in the dark with a low overpotential compared to that for oxidation of water (0.5 M H2SO4). The 0.294 V overpotential difference occurs despite the difference in standard redox potentials, ΔE = (E°(Cl2/Cl−) - E°(O2/H2O)), of 130 mV. Under 1 sun irradiation a photovoltage of ca. 0.566 V is achieved by comparing the illuminated n-Si/TiO2/Ir photoanode with the dark p+-silicon anode. Although the n-Si/TiO2/Ir photoanode is only one half of an eventual tandem cell needed for photosynthetic brine splitting, its ABPE for chloride oxidation is 1.42%, ca. 28 times that for water oxidation. The illuminated n-Si/TiO2/Ir photoanode remained stable at 1 mA cm−2 during a six-day chronopotentiometry test.

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