Conductance and capacitance of bilayer protective oxides for silicon water splitting anodes

Scheuermann, Andrew G.; Kemp, Kyle W.; Tang, Kechao; Lu, David; Satterthwaite, Peter F.; Ito, Tatsuro; Chidsey, Chrisopher E. D.; McIntyre, Paul C.

doi:10.1039/c5ee02484f

Cited by 44 publications

(75 citation statements)

References 45 publications

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“…[18,27] This is a slow process ranging from hours to days. In addition, catalyst layers of 1 to 2 nm of thickness [29][30][31] have been found to be sufficient to exhibit catalytic performance in the development of photocatalysts. With this reasoning, we have selected Raney nickel as the catalyst carrier for our studies.…”

Section: Introductionmentioning

confidence: 99%

Accelerated Durability Test for High‐Surface‐Area Oxyhydroxide Nickel Supported on Raney Nickel as Catalyst for the Alkaline Oxygen Evolution Reaction

et al. 2019

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We demonstrate a fit‐for‐purpose accelerated durability test (ADT) of a high‐surface‐area catalyst for the alkaline oxygen evolution reaction (OER). Using an automatized electrochemical setup enabled us to run a complex ADT protocol including online detection of the effective solution resistance as well as linear voltammetry, cyclic voltammetry, cyclic galvanograms, and electrochemical impedance spectroscopy (EIS) for 55 h in total. Using this protocol, we tested the service life stability of a nickel oxyhydroxide (NiOx) catalyst based on Raney Ni. The catalyst was prepared by growing nickel oxyhydroxide on high‐surface‐area Raney Ni and subsequent formation of the active phase. The successful synthesis of the active NiOx phase is supported by cyclic voltammetry and Raman spectroscopy. The as prepared and activated Raney NiOx exhibits an overpotential for the OER of 304 mV at 10 mA cm−2 with a Tafel slope of 53 mV dec−1 and roughness factors as high as 4515 determined by EIS during OER. By concentrating for the ADT protocol on current densities relevant for coupling water electrolysis to photovoltaics, it is demonstrated that Raney NiOx is a promising anode material candidate as it is earth abundant and its active phase exhibits high OER activity as well as stability.

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Section: Introductionmentioning

confidence: 99%

Accelerated Durability Test for High‐Surface‐Area Oxyhydroxide Nickel Supported on Raney Nickel as Catalyst for the Alkaline Oxygen Evolution Reaction

et al. 2019

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“…7,10 In this case, the only difference between the p + nSi photoanode and the p + Si anode reference will be the difference between hole and electron transport pathways affecting the reductive forward bias, as shown in Figure 5. For anodic operation, the two are now essentially identical.…”

Section: The Pmentioning

confidence: 99%

Understanding Photovoltage in Insulator-Protected Water Oxidation Half-Cells

Scheuermann

Chidsey

McIntyre

2015

J. Electrochem. Soc.

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In the pursuit of a photosynthetic and efficient water splitting device, detailed investigations of individual aspects of the whole device are necessary: catalysis, electronic conductivity, cathode and anode stability, and kinetics among other aspects. Improvement in one aspect can, however, often require fundamental tradeoffs affecting others. High solar-to-hydrogen efficiency of the overall system is the ultimate goal of water splitting research. When optimizing half-cells, either the anode or cathode, the photovoltage required to achieve a current density of interest is an especially important metric. This report investigates the photovoltage in insulator-protected water oxidation anodes using ALD-TiO 2 protected silicon devices as a case study and looks in depth at how photovoltage is correctly determined from typical electrochemical analysis and how this relates to the underlying solid-state carrier transport. Finally, the photovoltage at 10 mA/cm 2 referenced to the thermodynamic potentials is reviewed from several leading research reports for various photoanodes and photocathodes, providing a direct comparison of cell performance. Half-cell efficiency and photovoltage metrics.-The solar-tohydrogen (STH) efficiency is the most important metric for characterizing water splitting cells, and can be calculated in a variety of ways. When optimizing an anodic or cathodic half-cell, the impliedefficiencies are often reported as the product of the photovoltage and current, divided by the input solar power. The power point of an actual water splitting device, however, will be determined by current matching among the components, and also necessitates a minimum voltage to drive the reactions of interest. As such, implied half-cell efficiency plots as a function of voltage can include values that are not meaningful for full cell operation. As will be shown at the end of this report, most reported anodes and cathodes do not yet provide sufficient photovoltage for photosynthetic operation of full water-splitting cells, meaning the current stand-alone full cell efficiency is still zero.The closest metric to efficiency that can be easily compared from report to report and used to best imply final device operation is the photovoltage at a relevant current, namely the voltage given to or required from the rest of the device, including the other half cell, at a certain operating current. When the photovoltage is measured close to zero current, an approximation of the open-circuit photovoltage is obtained. When it is measured at a reasonable operating current like 10 mA/cm 2 , an approximation of the power given or needed at the max power point is obtained. The tables at the end of this report show the voltage provided from a given half-cell and needed from the other at 10 mA/cm 2 to illustrate these comparisons. Comparing experimental results to theory helps illustrate the difference between half-cell and full-device efficiency calculations and how to transform values between the two. Pinaud et al. have attempted to calculat...

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“…[7][8][9] Recently, we have investigated the tunnel barrier to hole transport presented by an interfacial layer (IL) of SiO2 in TiO2-protected Si photoanodes. 10 The SiO2 tunnel oxide can easily dominate the device resistance due to its large bandgap and relative lack of bulk oxide traps, compared to the TiO2 corrosion protection layer. Photovoltage design principles for two types of photoanodes, those employing nSi metal-insulator-semiconductor Schottky junctions and those employing p + nSi buried junctions (detailed diagrams in supporting S1), have also recently been characterized.…”

Section: Introductionmentioning

confidence: 99%

Engineering Interfacial Silicon Dioxide for Improved Metal–Insulator–Semiconductor Silicon Photoanode Water Splitting Performance

Satterthwaite

Scheuermann

Hurley

et al. 2016

ACS Appl. Mater. Interfaces

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Silicon photoanodes protected by atomic layer deposited (ALD) TiO2 show promise as components of water splitting devices that may enable the large-scale production of solar fuels and chemicals. Minimizing the resistance of the oxide corrosion protection layer is essential for fabricating efficient devices with good fill factor. Recent literature reports have shown that the interfacial SiO2 layer, interposed between the protective ALD-TiO2 and the Si anode, acts as a tunnel oxide that limits hole conduction from the photo-absorbing substrate to the surface oxygen evolution catalyst. Here-in we report a significant reduction of bilayer resistance, achieved by forming stable, ultrathin (< 1.3 nm) SiO2 layers, allowing fabrication of water splitting photoanodes with hole conductances near the maximum achievable with the given catalyst and Si substrate. Three methods for controlling the SiO2 interlayer thickness on the Si(100) surface for ALD-TiO2 protected anodes were employed: (1) TiO2 deposition directly on an HF-etched Si(100) surface, (2) TiO2 deposition after SiO2 atomic layer deposition on an HF-etched Si(100) surface, and (3) oxygen scavenging, post-TiO2 deposition to decompose the SiO2 layer using a Ti overlayer. Each of these methods provides a progressively superior means of reliably thinning the interfacial SiO2 layer, enabling the fabrication of efficient and stable water oxidation silicon anodes.

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Conductance and capacitance of bilayer protective oxides for silicon water splitting anodes

Abstract: State-of-the-art silicon water splitting photoelectrochemical cells employ oxide protection layers that exhibit electrical conductance in between that of dielectric insulators and electronic conductors, optimizing both built-in field and conductivity.

Cited by 44 publications

References 45 publications

Accelerated Durability Test for High‐Surface‐Area Oxyhydroxide Nickel Supported on Raney Nickel as Catalyst for the Alkaline Oxygen Evolution Reaction

Accelerated Durability Test for High‐Surface‐Area Oxyhydroxide Nickel Supported on Raney Nickel as Catalyst for the Alkaline Oxygen Evolution Reaction

Understanding Photovoltage in Insulator-Protected Water Oxidation Half-Cells

Engineering Interfacial Silicon Dioxide for Improved Metal–Insulator–Semiconductor Silicon Photoanode Water Splitting Performance

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