Technical Paper

Authors: 

Hunter, Bryan M.; Thompson, Niklas B.; Müller, Astrid M.; Rossman, George R.; Hill, Michael G.; Winkler, Jay R.; Gray, Harry B.

Journal: 

Joule

Year: 

2018

Abstract: 

We report in situ spectroscopic measurements in nonaqueous media designed to trap an exceptionally strong oxidant generated electrochemically from an iron-containing nickel layered double hydroxide ([NiFe]-LDH) material. Anodic polarization of this material in acetonitrile produces metal-oxo vibrational spectroscopic signatures along with an extremely narrow near-infrared luminescence peak that strongly indicate that the reactive intermediate is cis-dioxo-iron(VI). Chemical trapping experiments reveal that addition of H2O to the polarized electrochemical cell produces hydrogen peroxide; and, most importantly, addition of HO– generates oxygen. Repolarization of the electrode restores the iron(VI) spectroscopic features, confirming that the high-valent oxo complex is active in the electrocatalytic water oxidation cycle.

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Authors: 

Zhang, Bingchang; Jie, Jiansheng; Zhang, Xiujuan; Ou, Xuemei; Zhang, Xiaohong

Journal: 

ACS Applied Materials & Interfaces

Year: 

2017

Abstract: 

The development of silicon (Si) materials during past decades has boosted up the prosperity of the modern semiconductor industry. In comparison with the bulk-Si materials, Si nanowires (SiNWs) possess superior structural, optical, and electrical properties and have attracted increasing attention in solar energy applications. To achieve the practical applications of SiNWs, both large-scale synthesis of SiNWs at low cost and rational design of energy conversion devices with high efficiency are the prerequisite. This review focuses on the recent progresses in large-scale production of SiNWs, as well as the construction of high-efficiency SiNW-based solar energy conversion devices, including photovoltaic devices and photo- electrochemical cells. Finally, the outlook and challenges in this emerging field are presented.

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Authors: 

Cai, Guorui; Zhang, Wang; Jiao, Long; Yu, Shu-Hong; Jiang, Hai-Long

Journal: 

Chem

Year: 

2017

Abstract: 

The conversion of traditional metal-organic framework (MOF) nanocrystals to self-supporting and well-aligned MOF superstructures is highly desired for diverse functional applications but remains a significant challenge. In this work, we develop a versatile strategy for the controllable synthesis of three- dimensional MOF hybrid arrays by utilizing semiconducting nanostructures as self-sacrificing templates. Typically, different MOF nanorod or nanowall arrays on various substrates have been successfully fabricated. Particularly, MOF- hybrid-array-derived carbon-based composites with well-aligned hierarchical morphology and self-supporting structure can be directly applied to both an- odes and cathodes for water splitting. They exhibit excellent electrocatalytic performance and are superior to the pristine semiconducting arrays, as well as other MOF-based counterparts. This work provides a strategy for the rational assembly of well-aligned MOF arrays on various substrates, which could serve as a promising platform for diverse applications.

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Authors: 

Nicolas Kaeffer, Adina Morozan, and Vincent Artero

Journal: 

Journal of Physical Chemistry B

Year: 

2015

Abstract: 

We report here that a bioinspired cobalt diimine−dioxime molecular catalyst for hydrogen evolution immobilized onto carbon nanotube electrodes proves tolerant toward oxygen. The cobalt complex catalyzes O2 reduction with an onset potential of +0.55 V vs RHE. In this process, a mixture of water and hydrogen peroxide is produced in a 3:1 ratio. Our study evidences that such side-reductions have little impact on effectiveness of proton reduction by the grafted molecular catalyst which still displays good activity for H2 evolution in the presence of O2. The presence of O2 in the media is not detrimental toward H2 evolution under the conditions used, which simulate turn-on conditions of a water-splitting device.

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Authors: 

Brazzolotto, Deborah; Gennari, Marcello; Queyriaux, Nicolas; Simmons, Trevor R.; Pécaut, Jacques; Demeshko, Serhiy; Meyer, Franc; Orio, Maylis; Artero, Vincent; Duboc, Carole

Journal: 

Nature Chemistry

Year: 

2016

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Authors: 

Huan, Tran N.; Jane, Reuben T.; Benayad, Anass; Guetaz, Laure; Tran, Phong D.; Artero, Vincent

Journal: 

Energy Environ. Sci.

Year: 

2016

Abstract: 

Hydrogen/water interconversion is a key reaction in the context of new energy technologies, including hydrogen fuel cells, water electrolyzers, and water-splitting photoelectrochemical cells. Specifications differ for these technologies to meet economic viability but state-of-the-art prototypes all rely on the powerful catalytic properties of the platinum metal as a catalyst for hydrogen production and uptake. Yet, this scarce and expensive metal is not itself a sustainable resource and its replacement by low cost and readily available materials is a requisite for these technologies to become economically viable. Here we revisit the preparation of bioinspired nanomaterials for hydrogen evolution and uptake (Le Goff et al., Science, 2009, 326, 1384–1387) and show that molecular engineering combined with three dimensional structuring of the electrode material allows the preparation of stable materials based on nickel bisdiphosphine catalytic units with performances in a 0.5 M sulphuric acid aqueous electrolyte that approach those of commercial platinum-based materials (0.05 mgPt cm 2) assessed under similar, technologically relevant, operational conditions.

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Authors: 

Kaeffer, Nicolas; Massin, Julien; Lebrun, Colette; Renault, Olivier; Chavarot-Kerlidou, Murielle; Artero, Vincent

Journal: 

Journal of the American Chemical Society

Year: 

2016

Abstract: 

Dye-sensitized photoelectrochemical cells (DS-PECs) for water splitting hold promise for the large- scale storage of solar energy in the form of (solar) fuels, owing to the low cost and ease to process of their constitutive photoelectrode materials. The efficiency of such systems ultimately depends on our capacity to promote unidirectional light-driven electron transfer from the electrode substrate to a catalytic moiety. We report here on the first noble-metal free and covalent dye− catalyst assembly able to achieve photoelectrochemical visible light-driven H2 evolution in mildly acidic aqueous conditions when grafted onto p-type NiO electrode substrate.

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Authors: 

He, Yumin; Thorne, James E.; Wu, Cheng Hao; Ma, Peiyan; Du, Chun; Dong, Qi; Guo, Jinghua; Wang, Dunwei

Journal: 

Chem

Year: 

2016

Abstract: 

Tantalum nitride (Ta3N5) is a promising photoelectrode for solar water splitting. Although near-theoretical-limit photocurrent has already been reported on Ta3N5, its low photovoltage and poor stability remain critical challenges. In this study, we used Ta3N5 nanotubes as a platform to understand the origins of these issues. Through a combination of photoelectrochemical and high-resolution electron microscope measurements, we found that the self-limiting surface oxidation of Ta3N5 resulted in a thin amorphous layer (ca. 3 nm), which proved to be effective in pinning the surface Fermi levels and thus fully suppressed the photoactivity of Ta3N5. X-ray core-level spectroscopy characterization not only confirmed the surface composition change resulting from the oxidation but also revealed a Fermi-level shift toward the positive direction by up to 0.5 V. The photoactivity degradation mechanism reported here is likely to find applications in other solar-to-chemical energy-conversion systems.

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