Combinatorial high-throughput optical screening for optimum composition of highly active ruthenium based ternary catalysts in oxygen reduction reaction

A series of combinatorial optical screening analysis was operated, first for the selection of metal candidates for the ternary Ru-based catalyst and later for the selection of optimized compositions with high performance towards ORR. Among the binary Ru-based catalysts, combinations with Co and Se exhibited the highest performance towards ORR. To investigate a possible synergic effect from the selected metals, the ternary Ru-based combinatorial optical screening was preceded. Among the various combinations and compositions, the optimum composition towards ORR for ternary Ru-Se-Co based catalyst was chosen at 73:12:15 = Ru:Se:Co at. % (named RSC-1). The RSC-1 catalyst measured a current density of −1.28 mAcm−2 at 0.75 V (vs. RHE), which was about 5 times higher than that of Ru/C (−0.26 mA cm−2). The mass activity of RSC-1 (12.20 mA mg−1) had an enhanced performance of about 6.8 times than that of Ru/C (1.78 mA mg−1) at 0.75 V (vs. RHE). It was deduced that a synergic effect between the repulsion of oxy-species on the Ru atoms by Se and the alternation of electron configuration by Co, the adequate amounts of Co and Se in the ternary Ru-Se-Co based catalyst could have induced the enhanced ORR performance of the RSC-1 catalyst.