Pt atoms on doped carbon nanosheets with ultrahigh N content as a superior bifunctional catalyst for hydrogen evolution/oxidation

Pt single-atom catalysts (SACs) have shown great potential for electrochemical catalysis. However, no systematic study of their bifunctional catalytic activity for the hydrogen evolution reaction (HER) and the hydrogen oxidation reaction (HOR) has yet been published. More significantly, the reported catalytic capabilities of Pt SACs have almost been exclusively measured using a rotating disk electrode (RDE) with a three-electrode configuration, which does not accurately reflect the catalysts' performance during operation within single-cell devices. Herein, we demonstrate the immobilization of isolated Pt atoms on a carbon nanosheet support doped with ultrahigh N content (12.1 at%; Pt/NCS) to create a bifunctional HER/HOR catalyst. Compared with commercial Pt/C, the developed Pt/NCS catalyst delivered high utilization as well as excellent mass activity enhancement and stability for both reactions. As a final test, a rigorous catalyst evaluation was conducted in both a proton exchange membrane (PEM) electrolyzer and a PEM fuel cell. As expected, with only half the Pt loading of commercial Pt/C, Pt/NCS-based electrodes in the electrolyzer and the fuel cell still exhibited slightly better performance than those based on Pt/C. This work constitutes a huge step from the academic study of Pt-based SCAs to their industrial application, and it focuses more attention on the harsh evaluation and optimization of SACs within commercial-scale devices.