A Regenerative Coking and Sulfur Resistant Composite Anode with Cu Exsolution for Intermediate Temperature Solid Oxide Fuel Cells

Abstract

A Cu exsolution based composite anode (R-LSFCNb) was prepared through reducing perovskite La 0.5 Sr 0.5 Fe 0.8 Cu 0.15 Nb 0.05 O 3-δ (LSFCNb) in H 2 for intermediate temperature solid oxide fuel cells (IT-SOFC). The performance and stability of the anode in various fuels, as well as the regeneration possibility from coking in syngas were investigated. The anode showed highly catalytic activity to fuel oxidations by peak power density of 0.76, 0.64, and 0.71 W • cm −2 in wet H 2 (3% H 2 O), wet syngas (H 2 :CO = 1, 3% H 2 O), and H 2 with 50 ppm H 2 S, respectively, at 800 • C in electrolyte supported full cells. Moreover, the anode was highly stable in wet H 2 , and exhibited H 2 S and coking resistance during 100 h testing period under 0.7 V. In addition, the anode can be regenerated from carbon deposition in wet syngas through applying reodx cycles on it, the evolution and elimination of carbon deposition in the anode were studied and discussed.

Emergence and Future of Exsolved Materials

“…However, in an attempt to make controllable copper exsolution possible, various matrixes have been employed including chromates, [74,126] titanates, [13,127] or ferrites. [128] Cu exsolution studies remain very limited in number, accounting for only about 5% of the non-noble metal-based studies published.…”

“…The stable redox performance of the oxygen carriers is attributed to the reversible exsolution and reincorporation of Cu nanoparticles however oxidizing the reduced materials with CO 2 only is not sufficient to reincorporate the Cu nanoparticles and an additional air oxidation step is required. [129] Cu exsolution has also been used for electrochemical applications, where the main advantages highlighted in literature included coke and sulfur resistant [128] performance in reversible, intermediate temperature SOFCs, agglomeration resistant properties in high temperature steam electrolysis [13,127] and increased conductivity and stability in ceramic fuel electrodes. [13] This was mainly attributed to the synergetic effect of the metallic catalyst and the ceramic support as well as a shortening in the diffusion length of free electrons in the ceramic, which has been shown to favor the conductivity increase of the samples.…”

“…Cu exsolution has also been used for electrochemical applications, where the main advantages highlighted in literature included coke and sulfur resistant [ 128 ] performance in reversible, intermediate temperature SOFCs, agglomeration resistant properties in high temperature steam electrolysis [ 13,127 ] and increased conductivity and stability in ceramic fuel electrodes. [ 13 ] This was mainly attributed to the synergetic effect of the metallic catalyst and the ceramic support as well as a shortening in the diffusion length of free electrons in the ceramic, which has been shown to favor the conductivity increase of the samples.…”

Progress of Exsolved Metal Nanoparticles on Oxides as High Performance (Electro)Catalysts for the Conversion of Small Molecules

“…The exsolution of B‐site metal particles is reported to be promoted by the phase transformation of oxide precursors. [ 28,62,63,75,76,80,96,101,125,134,157,162,164,174,203–207 ] After thermal reduction in reducing atmospheres, certain single or double‐layered perovskite oxides can be partially or completely converted into to R‐P perovskites with concomitant B‐site exsolution to the surface. The reaction describing this conversion can be described by the following equations …”

Metal Exsolution to Enhance the Catalytic Activity of Electrodes in Solid Oxide Fuel Cells

“…Electronic conductivity can be achieved in composites with electronic conductors other than Ni. For example, Cu has been investigated as an electronic conducting material in the anode of SOFCs that oxidize hydrocarbons directly, without first reforming to form a hydrogen rich gas [17][18][19]. This is possible because Cu, unlike Ni, does not catalyze the formation of carbon fibers.…”