Characterization of Pt catalysts on Nb-doped and Sb-doped SnO2–δ support materials with aggregated structure by rotating disk electrode and fuel cell measurements

Abstract We found high activity and durability for oxide-supported Pt catalysts for the oxygen reduction reaction (ORR). These catalysts were supported on Sn 0.96 Nb 0.04 O 2– δ (Pt/Sn 0.96 Nb 0.04 O 2– δ ; BET area of support, 37 m 2  g −1 ; Pt loading, 10.0 wt%) and Sn 0.96 Sb 0.04 O 2– δ (Pt/Sn 0.96 Sb 0.04 O 2– δ ; BET area of support, 33 m 2  g −1 ; Pt loading, 12.3 wt%), by use of the rotating disk electrode (RDE) technique, and measured the I–E performance of single H 2 -air polymer electrolyte fuel cells (PEFCs) using these catalysts as the cathode. The nanoparticulate supports Sn 0.96 Nb 0.04 O 2– δ and Sn 0.96 Sb 0.04 O 2– δ had an aggregated structure similar to that of carbon black (CB). The electrochemically active surface area of Pt, estimated by cyclic voltammetry measurements with the RDE, reached 79.7 m 2  g −1 (Pt/Sn 0.96 Nb 0.04 O 2– δ ) and 68.6 m 2  g −1 (Pt/Sn 0.96 Sb 0.04 O 2– δ ). The ORR activity of Pt/Sn 0.96 Nb 0.04 O 2– δ exceeded that of a commercialized Pt catalyst supported carbon black (Pt/CB). Higher durability was confirmed for Pt/Sn 0.96 Nb 0.04 O 2– δ and Pt/Sn 0.96 Sb 0.04 O 2– δ compared to that of Pt/CB with a test protocol for start/stop cycling recommended by the Fuel Cell Commercialization Conference of Japan (FCCJ) [1] . Single cells using these catalysts showed I–E performance superior to that for the Pt/CB at operating potentials above 0.4 V. For operating potentials below 0.4 V, a slight amount of Sn dissolution from the Sn 0.96 Sb 0.04 O 2– δ support occurred, resulting in degradation of the cell performance due to Pt poisoning by Sn re-deposition, but no noticeable degradation at Sn 0.96 Nb 0.04 O 2– δ was found, due to the suppressed Sn dissolution.