Active sites engineering of Pt/CNT oxygen reduction catalysts by atomic layer deposition

Understanding carbon-supported Pt-catalyzed oxygen reduction reaction (ORR) from the perspective of the active sites is of fundamental and practical importance. In this study, three differently sized carbon nanotube-supported Pt nanoparticles (Pt/CNT) are prepared by both atomic layer deposition (ALD) and impregnation methods. The performances of the catalysts toward the ORR in acidic media are comparatively studied to probe the effects of the sizes of the Pt nanoparticles together with their distributions, electronic properties, and local environments. The ALD-Pt/CNT catalysts show much higher ORR activity and selectivity than the impregnation-Pt/CNT catalysts. This outstanding ORR performance is ascribed to the well-controlled Pt particle sizes and distributions, desirable Pt⁰ 4f binding energy, and the Cl-free Pt surfaces based on the electrocatalytic measurements, catalyst characterizations, and model calculations. The insights reported here could guide the rational design and fine-tuning of carbon-supported Pt catalysts for the ORR.