Study of Ni-YSZ anode under pure and diluted NH3 conditions towards NO production

Abstract

Direct ammonia solid oxide fuel cells (DA-SOFCs) have been widely recognized as highly efficient energy conversion devices. Their application to the reduction and valorisation of nitrous oxide (N2O), a potent greenhouse gas, represents a promising strategy for mitigating global warming while simultaneously addressing energy demands. The present work extends this concept by investigating an Sr2Fe1.5Mo0.5O6-delta vertical bar vertical bar CGO vertical bar vertical bar YSZ vertical bar vertical bar Ni-YSZ solid oxide fuel cell (SOFC), providing insight into the simultaneous electrochemical reduction of N2O at the cathode and the electrochemical oxidation of NH3 at the anode. This approach aligns with the objective of achieving N2O abatement and valorisation through the production of NO at the anode, a valuable intermediate in the nitric acid synthesis process. In this study, the anodic reaction is examined for different fuel compositions, ranging from pure NH3 to 6 % of NH3 balanced in N-2, at an intermediate operating temperature of 750 degrees C. The results indicate that fuel dilution had no significant impact on the overall electrical performance of the cell, as decreasing the ammonia concentration from pure NH3 to 10 % NH3 led to only a moderate reduction in power density, from 75 to 62 mW cm(-2). Notably, operation under diluted fuel conditions enabled the electrochemical oxidation of NH3 to produce NO, which makes operation under diluted conditions attractive. Concurrently, nitrous oxide decomposition at the cathode was ca. 10 %, which, although modest, is a promising result considering the high thermal stability of the N2O molecule.