Enhancing Ni Exsolution by Nonmetal B‑Site Substituents (Si and P) in SrTiO3‑Based Solid Oxide Fuel Cell Anodes
journal contributionposted on 2021-09-01, 22:13 authored by Md Raziun Bin Mamtaz, Zheng Wang, Alessio Belotti, Emanuele Quattrocchi, Jing Yu, Jiapeng Liu, Francesco Ciucci
In situ nanoparticle exsolution is an excellent strategy to enhance the electrocatalytic activity of solid oxide fuel cell (SOFC) electrodes. Herein, we report that Si and P can be used as B-site nonmetal substituents to improve the electrochemical performance of the model SOFC anode SrTiO3−δ after testing different Si- and P-substitution levels. First-principles calculations show that Si- or P-substitution promotes the Ni diffusion as well as its segregation toward the surface. Related experiments show that the area-specific resistance (ASR) measured at 800 °C in 3% humidified H2 improves upon Si- and P-substitution from 0.600 Ω cm2 for Sr0.8Ti0.9Ni0.1O3−δ (STN) to 0.061 Ω cm2 for Sr0.8Ti0.85Ni0.1Si0.05O3−δ and 0.056 Ω cm2 for Sr0.8Ti0.85Ni0.1P0.05O3−δ. Moreover, the P-substituted material shows excellent stability with a symmetric cell, retaining its ASR for 70 h in 3% humidified H2. X-ray photoelectron spectroscopy measurements reveal that even a slight nonmetal substitution can reduce Ni to a lower oxidation state than STN before exsolution. In turn, this promotes the reduction of Ni during exsolution, which improves the ASR. For the first time, nonmetal substituents in perovskite oxides are utilized to aid Ni exsolution from the host lattice, opening new avenues to improve the electrochemical activity.
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