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

Kinetically sluggish ammonia oxidation and interference of H 2 competing with NH 3 active sites will suppress the output performance of direct ammonia solid oxide fuel cell (DA-SOFC). Herein, we select Zn 2+ doped into Pr 2 NiO 4 as precursor of Pr 2 Ni 1-x Zn x O 4 (PNZx) that can be destroyed and converted into Pr 2 O 3 together with in-situ Ni reduction, realizing the redistribution of elements in reduction atmosphere. Meanwhile, the foreign Zn 2+ as a low-valent element is retained in Pr 2 O 3 lattice due to the high segregation Gibbs free energy to form Ni/Pr 2-x Zn x O 3 , which aggravates the change of Pr 3+ and Pr 4+ , thus enhancing the oxygen vacancy concentration. The Zn 2+ promotes the reduction of Ni and quenches the adsorption capacity of H 2 , 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 −2 at 800 ℃, which is more than twice higher than that of Ni/YSZ. Various characterizations reveal that the NH 3 reaction path is the synergistic occurrence of ammonia decomposition and ammonia oxidation. • Realizing the redistribution of elements over Pr 2 Ni 1-x Zn x O 4 precursor by in-situ Ni exsolution. • Zn 2+ retained in Pr 2 O 3 lattice aggravates the change of Pr 3+ /Pr 4+ related to oxygen vacancies. • Foreign Zn 2+ quenches H 2 adsorption capacity and alleviates “hydrogen poisoning” behavior. • NH 3 -SOFCs shows comparable activity with H 2 due to the multi-functional effect of Pr 2 Ni 1-x Zn x O 4 .