Composite titanate cathode decorated with heterogeneous electrocatalytic sites towards efficient carbon dioxide electrolysis

Abstract

The coupling of surface oxygen vacancies with nano-sized metal can effectively improve the catalytic activity of heterogeneous catalysts. In this work, a high concentration of oxygen vacancies is created in Mn-doped titanate cathode, then iron nanoparticles are exsolved to anchor on the titanate surface and combine the surface oxygen vacancies to form heterogeneous catalysis clusters. The active Mn in the B site of the redox-stable Sr_0.95Ti_0.8Nb_0.1Mn_0.1O_3.00 (STNMO) creates 0.15 mol oxygen vacancies in the reduced Sr_0.95Ti_0.8Nb_0.1Mn_0.1O_2.85. With iron doping in the B site, it is found that the exsolution and dissolution of the iron nanoparticles are completely reversible on the titanate surface in redox cycles. The presence of iron nano crystal remarkably increases the ionic conductivity of the titanate solid solution by 0.5 orders of magnitude at intermediate temperatures. Promising electrode polarizations are obtained based on the titanate cathode decorated with heterogeneous electrocatalytic clusters in symmetric cells. The current efficiencies of direct carbon dioxide electrolysis reach as high as 90% in an oxide-ion conducting solid oxide electrolyzer at high temperatures.