Switching on electrocatalytic activity in solid oxide cells
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Solid oxide cells (SOCs) can operate with high efficiency in two ways—as fuel cells, oxidizing a fuel to produce electricity, and as electrolysis cells, electrolysing water to produce hydrogen and oxygen gases. Ideally, SOCs should perform well, be durable and be inexpensive, but there are often competitive tensions, meaning that, for example, performance is achieved at the expense of durability. SOCs consist of porous electrodes—the fuel and air electrodes—separated by a dense electrolyte. In terms of the electrodes, the greatest challenge is to deliver high, long-lasting electrocatalytic activity while ensuring cost- and time-efficient manufacture. This has typically been achieved through lengthy and intricate ex situ procedures. These often require dedicated precursors and equipment; moreover, although the degradation of such electrodes associated with their reversible operation can be mitigated, they are susceptible to many other forms of degradation. An alternative is to grow appropriate electrode nanoarchitectures under operationally relevant conditions, for example, via redox exsolution. Here we describe the growth of a finely dispersed array of anchored metal nanoparticles on an oxide electrode through electrochemical poling of a SOC at 2 volts for a few seconds. These electrode structures perform well as both fuel cells and electrolysis cells (for example, at 900 °C they deliver 2 watts per square centimetre of power in humidified hydrogen gas, and a current of 2.75 amps per square centimetre at 1.3 volts in 50% water/nitrogen gas). The nanostructures and corresponding electrochemical activity do not degrade in 150 hours of testing. These results not only prove that in operando methods can yield emergent nanomaterials, which in turn deliver exceptional performance, but also offer proof of concept that electrolysis and fuel cells can be unified in a single, high-performance, versatile and easily manufactured device. This opens up the possibility of simple, almost instantaneous production of highly active nanostructures for reinvigorating SOCs during operation.
Myung , J , Neagu , D , Miller , D N & Irvine , J T S 2016 , ' Switching on electrocatalytic activity in solid oxide cells ' Nature , vol Early View . DOI: 10.1038/nature19090
Copyright 2016 the Authors. This work is made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://dx.doi.org/10.1038/nature19090
The authors acknowledge support from the Engineering and Physical Sciences Research Council (EPSRC) Platform (grant EP/K015540/1), the EPSRC Material World Network (EP/J018414/1), EPSRC SUPERGEN Projects (EP/K021036/1 and EP/G01244X/1), EPSRC Capital for Great Technologies grant (EP/L017008/1) and a Royal Society Wolfson Merit Award (WRMA2012/R2). Further details of the methods and data used are at http://dx.doi.org/10.17630/c93efdb1-65a9-4f39-9277-2f56580d3b77.
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