Acidity of surface-infiltrated binary oxides as a sensitive descriptor of oxygen exchange kinetics in mixed conducting oxides

Silica: ubiquitous poison of metal oxide interfaces

“…111 Similar to findings of how Si-impurities impact grain boundaries, space charge regions induced by Si-impurities on oxide surface depleted of electrons, are reported to markedly lower surface oxygen exchange rates. 132 Particularly for the case of SMOXbased sensors, 132 VOSCs reportedly can preferentially block specific surface sites, leading to depressed surface interactions with oxygen. 95,96 Guided by such poisoning models, various mitigation methods have been developed.…”

“…[129][130][131] The authors recently reported the ability to predict whether a surface binary oxide additive on the surface of mixed conducting Pr 0.1 Ce 0.9 O 2−δ would result in surface electron depletion or accumulation, depending on its Smith acidity factor (Figure 9b) relative to the pristine oxide. 132 Indeed, while the oxygen exchange rate kchem was found to be suppressed by a factor of roughly 220 by strongly acidic SiO2, strongly basic additive Li2O, resulted in a thousand-fold increase, Figure 9a. More generally, the authors demonstrated that the Smith acidity scale allows one to predict, a-priori, the effect of binary oxide additives on the oxygen exchange rates of mixed conducting oxides.…”

“…More generally, the authors demonstrated that the Smith acidity scale allows one to predict, a-priori, the effect of binary oxide additives on the oxygen exchange rates of mixed conducting oxides. 132 Moreover, the negative impact of Si-poisons on kchem occurred even though surface coverage of the Si-poison was not continuous. No change in the activation energy was found, unlike recent studies in which thin siliceous layers significantly degraded performance and practically doubled the activation energy.…”

“…67 Recent findings indicate that finely dispersed high acidity Si-species also contribute to the formation of space charge regions (electron depleted) on the surface, decreasing oxygen exchange kinetics. 132 Despite the widespread detrimental effects of Si-species on performance of a This journal is © The Royal Society of Chemistry 20xx…”

Performance modulation through selective, homogenous surface doping of lanthanum strontium ferrite electrodes revealed by in situ PLD impedance measurements

“…Here, mostly perovskite-type mixed ion and electron conducting (MIECs) cathode materials, such as La 1-x Sr x CoO 3-δ (LSC), [9][10][11][12][13][14][15][16] La 1-x Sr x FeO 3-δ (LSF), [17][18][19][20][21] La 1-x Ba x CoO 3-δ (LBC), 22,23 Sm 1-x Sr x CoO 3-δ (SSC) [24][25][26] , La 1-x Sr x Co 1-y Fe y O 3-δ (LSCF) [27][28][29][30][31][32] , SrTi 1-x Fe x O 3-δ , (STF) [33][34][35][36] or Ba 1-x Sr x Co 1-y Fe y O 3-δ (BSCF) [37][38][39] were investigated. In addition, studies on Pr 1-x Ce x O 2-δ (PCO) 40,41 , NdNi 2 O 4+δ (NNO) 42,43 or La 2 NiO 4+δ (LNO) 44,45 have been conducted.…”