La-based perovskites for capacity enhancement of Li-O2 batteries

Li-O2 batteries are a promising technology for the upcoming energy storage requirements because of their high theoretical specific energy density of 11,680 Wh kg-1. Currently, the actual capacity of Li-O2 batteries is much lower than this theoretical value. In many studies, perovskites have been applied as catalysts to improve the air electrode reactions in Li-O2 batteries. The effects of structure and doping on the catalytic activity of perovskites are still unclear. La1-xSrxCoO3-δ (x = 0.1, 0.3, and 0.5) and La0.9Sr0.1YbO3-δ mixed with carbon black (Vulcan XC500 or Super P) were used as air electrode catalysts. Electrochemical characterizations were conducted using a Swagelok-type cell. The charge-discharge capacity and cyclic voltammetry (CV) performance were investigated in this study. The La1-xSrxCoO3-δ (x = 0.1, 0.3, and 0.5) is a suitable cathode catalyst for Li-O2 batteries. In this study, the La0.5Sr0.5CoO3-δ/Super P cathode demonstrated the highest discharge capacity (6,032 mAh g-1). This excellent performance was attributed to the large reaction area and enhanced Li2CO3 generation.

Oxygen vacancy-engineered titanium-based perovskite for boosting H(2)O activation and lower-temperature hydrolysis of organic sulfur

Modulation of water activation is crucial to water-involved chemical reactions in heterogeneous catalysis. Organic sulfur (COS and CS₂) hydrolysis is such a typical reaction involving water (H₂O) molecule as a reactant. However, limited by the strong O-H bond in H₂O, satisfactory CS₂ hydrolysis performance is attained at high temperature above 310 °C, which is at the sacrifice of the Claus conversion, strongly hindering sulfur recovery efficiency improvement and pollution emissions control of the Claus process. Herein, we report a facile oxygen vacancy (V_O) engineering on titanium-based perovskite to motivate H₂O activation for enhanced COS and CS₂ hydrolysis at lower temperature. Increased amount of V_O contributed to improved degree of H₂O dissociation to generate more active -OH, due to lower energy barrier for H₂O dissociation over surface rich in V_O, particularly V_O clusters. Besides, low-coordinated Ti ions adjacent to V_O were active sites for H₂O activation. Consequently, complete conversion of COS and CS₂ was achieved over SrTiO₃ after H₂ reduction treatment at 225 °C, a favorable temperature for the Claus conversion, at which both satisfying COS and CS₂ hydrolysis performance and improved sulfur recovery efficiency can be obtained simultaneously. Additionally, the origin of enhanced hydrolysis activity from boosted H₂O activation by V_O was revealed via in-depth mechanism study. This provides more explicit direction for further design of efficacious catalysts for H₂O-involved reactions.