Electrochemically-assisted NOx storage–reduction catalysts

• Nanodispersed NSR catalysts were coated in the porosity of Diesel Particulate Filters.
• Pt and Rh nanoparticles were supported on YSZ and GDC, two ionic conductors.
• Improved NOx removal efficiency was obtained.
• Analysis of reaction products gives first insight into mechanisms.
• Electrocatalytic processes are probably activated, even without polarization.

Supported noble-metal catalysts are extensively used in industry, particularly for car exhaust treatments. The challenge is to maximize the catalytic efficiency while minimizing the noble metal loading. Recent advances from the literature propose the use of electropromoted nanodispersed catalysts in order to assist catalytic reactions with electrochemical mechanisms: this type of catalyst design, inspired from fuel cells, combines electrochemical promotion of catalysis and high metallic active site availability. This paper explores whether electrochemical effects can improve the catalytic performances of nanodispersed NOx storage and reduction (NSR) catalysts deposited in the porosity of SiC mini-DPFs. NSR catalysts were elaborated employing Pt and Rh nanoparticles as electrodes, supported on yttria stabilized zirconia (YSZ) or gadolinium doped cerium oxide (GDC) nanoparticles (electrolyte), and used for NOx abatement in diesel exhaust gas conditions. Improved NOx removal efficiency was obtained. Comparison of YSZ (ionic conductor) and GDC (mixed ionic and electronic conductor) electrolytes showed that GDC-based catalytic nano-cells present the highest catalytic activities. A detailed analysis of the reaction products showed that electrochemical reactions can take place on nano-electrodes, in addition to catalytic reactions.

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