Unveiling optimal activity and mechanism of in situ Ni reduction Pr2Ni1-xZnxO4 anode for ammonia solid oxide fuel cells

Abstract

Kinetically sluggish ammonia oxidation and interference of H competing with NH active sites will suppress the output performance of direct ammonia solid oxide fuel cell (DA-SOFC). Herein, we select Zn doped into PrNiO as precursor of PrNiZnO (PNZx) that can be destroyed and converted into PrO together with in-situ Ni reduction, realizing the redistribution of elements in reduction atmosphere. Meanwhile, the foreign Zn as a low-valent element is retained in PrO lattice due to the high segregation Gibbs free energy to form Ni/PrZnO, which aggravates the change of Pr and Pr, thus enhancing the oxygen vacancy concentration. The Zn promotes the reduction of Ni and quenches the adsorption capacity of H, alleviating the “hydrogen poisoning” behavior. As a result, the maximum powder density of single cell based on PNZ0.1 supported by YSZ electrolyte is 134 mW·cm at 800 ℃, which is more than twice higher than that of Ni/YSZ. Various characterizations reveal that the NH reaction path is the synergistic occurrence of ammonia decomposition and ammonia oxidation.