(Invited) Enhanced Steam Electrolysis at Exsolution Titanates

B-site doped, A-site deficient perovskite titanate oxides with formula  (M = Ni²⁺ or Fe³⁺; x = 0.06; g = (4-n)x/2) were employed as solid oxide electrolysis cell (SOEC) cathodes for hydrogen production via high temperature steam electrolysis (HTSE) at 900 °C. A proportion of B-site dopants were exsolved at the surface in the form of metallic nanoparticles under SOEC operating (reducing) conditions, due in part to the inability of the host lattice to accommodate vacancies (introduced (d) oxygen vacancies () and fixed A-site () and inherent (g) oxygen vacancies) beyond a certain limit. The presence of electrocatalytically active Ni⁰ or Fe⁰ nanoparticles and higher  concentrations dramatically lowered the activation barrier to steam electrolysis and led to sharp rises in oxide ion mobility compared to the parent material (x = 0). La_0.4Sr_0.4Ni_0.06Ti_0.94O_2.94 demonstrated discontinuous temperature dependence possibly due to oxygen vacancy trapping at lower temperatures.