Experimental investigation into tungsten carbide thin films as solid oxide fuel cell anodes
- PDF / 921,501 Bytes
- 10 Pages / 584.957 x 782.986 pts Page_size
- 111 Downloads / 170 Views
Judith Lattimerb) Department of Chemistry & Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA
Cynthia Friend John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA; and Department of Chemistry & Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA
Atul Verma and Masaru Tsuchiya SiEnergy Systems LLC, Cambridge, Massachusetts 02110, USA
Shriram Ramanathan John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA; and School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USA (Received 15 May 2016; accepted 16 August 2016)
Refractory carbides possess metal-like electronic and catalytic properties, which make them interesting candidates for anodes in solid oxide fuel cells. However, significant challenges include phase instability due to electrochemical potential gradient driven oxidation. This requires an understanding of both the chemical thermodynamics in operating environments along with direct measurement of the catalytic activity in fuel mixtures. Here, we present an experimental study on nanostructured WC as an anode for solid oxide fuel cells operating at 300–500 °C. This is enabled by combining calculated thermochemical equilibria validated against experiments at the material level and in fuel cell devices combined with flow reactor studies on fuel-selective catalytic activity directly at working anode interfaces. With an optimized anode microstructure and hydrogen–methane fuel mixtures, WC anode-based solid oxide fuel cells are shown to achieve a near-ideal open circuit voltage of 1.1 V at 500 °C.
I. INTRODUCTION
Research in electrodes for solid oxide fuel cells (SOFCs) is an active field spanning materials synthesis, physical chemistry, and electrochemistry.1 While reduced operating temperatures in the 300–500 °C range could enable the use of solid oxide fuel cells for portable applications, many elementary processes that are thermally activated may suffer, leading to diminished power density. Hence, there is a great need to explore new materials that can perform as catalysts for fuel oxidation and moreover develop fundamental understanding of reaction phenomena under dynamic conditions. Noble metals such as Pt or Ru make excellent catalysts at these temperature ranges. However, they suffer from morphological instability.2–4 Group IV–VI transition metal carbides are interesting candidate systems as they Contributing Editor: Edward M. Sabolsky a) Address all correspondence to this author. e-mail: [email protected] b) These authors contributed equally to this work. DOI: 10.1557/jmr.2016.312
show properties of both ceramics and metals.5–7 In particular, carbides of tungsten are widely used engineering materials in wear-resistant applications due to their refractory nature. WC shows high hardness, high melting temperature, and low friction co-efficient, which suggests long term microstructural stability at high operating temp
Data Loading...
