MSE Grad Talks: Toluwalope John, Boston University

Speaker: Toluwalope John, Boston University

Title: Nanoscale Engineering of the Oxygen Electrode in Solid Oxide Cells: Barrier-Layer-Free Ruddlesden–Popper Nickelate Infiltration for Intermediate-Temperature Performance and Durability

Abstract: Solid oxide cells (SOCs) are promising electrochemical devices for high-efficiency power generation and reversible green hydrogen production. A critical barrier to their widespread deployment is the trade-off between operating temperature and electrode performance: reducing temperature to the intermediate range (600–800 °C) improves materials durability but severely limits electrochemical activity, particularly at the air electrode where the oxygen reduction and evolution reactions exhibit high activation energy. Conventional LSM–YSZ composite oxygen electrodes suffer from negligible oxide-ion conductivity and sluggish surface exchange kinetics at these operating conditions. Meanwhile, direct integration of high- activity Ruddlesden–Popper (RP) nickelate oxides with YSZ electrolytes is hindered by chemical incompatibility and detrimental interfacial phase formation, necessitating a barrier layer between the electrode and electrolyte. This talk presents a nanoscale liquid-infiltration strategy that sidesteps that trade-off: depositing electrocatalytically active Ln–Ni–O (Ln = La, Nd, Pr) nanoparticles into pre-sintered LSM–YSZ scaffolds, without barrier layers or new architectures. Using electrochemical impedance spectroscopy and distribution-of-relaxation-times (DRT) analysis on symmetrical cells, I will discuss how the choice of lanthanide controls phase purity, chemical compatibility with YSZ, and which elementary electrode processes are accelerated, with Nd–Ni–O emerging as the best-balanced infiltrate. I will then present the performance of Nd₂NiO₄₊δ-infiltrated cells in full anode-supported SOEC operation at –1 A cm⁻², where they show both lower initial polarization and substantially reduced degradation over ~250 h, traced via DRT and post-mortem microscopy to suppression of electrode–electrolyte delamination. I will close with what these results suggest for designing durable and scalable intermediate-temperature SOCs.

Bio: Toluwalope John is a fourth year PhD. candidate in the Department of Mechanical Engineering at Boston University, advised by Prof. Srikanth Gopalan. His doctoral research focuses on nanoscale engineering of solid oxide cell electrodes using liquid-solution infiltration and atomic layer deposition to push high-performance, durable operation down to intermediate temperatures (600–800 °C)