Cobalt single atom site isolated Pt nanoparticles for efficient ORR and HER in acid media

Abstract

Hitherto, developing an economical and stable high-activity bifunctional Pt catalyst for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) becomes necessary for fuel cells and regeneration fuel cell system. However, how to uniformly disperse and firmly fix Pt nanoparticles (NPs) on carbon support with optimal particle size for catalysis is still a big challenge. Herein, by taking advantage of the isolating effect of the cobalt (Co) single atom site to Pt, strong interaction between Co single atoms and Pt, and the confinement of the porous carbon matrix derived metal organic frameworks, we successfully evenly immobilize Pt NPs on ZnCo-ZIF originated porous nitrogen-doped carbon matrix with rich cobalt single atoms (Co SAs-ZIF-NC) as multiple active sites. Compared with the commercial Pt/C catalyst, Pt@Co SAs-ZIF-NC, with ultralow Pt loading and ideal particle size, not only increases the active center, but also promotes the catalysis kinetics, greatly improving the ORR and HER catalytic activity. Under acidic conditions, its half-wave potential (0.917 V) is superior to commercial Pt/C (0.868 V), and the mass activity (0.48 A per mgPt) at 0.9 V is 3 times that of Pt/C (0.16 A per mgPt), surpassing the U.S. DOE target of 0.44 A per mgPt. Besides, it also shows outstanding HER performance. At 20 and 30 mV, its mass activity is even 4.5 and 13.6 times that of Pt/C. When further employed for HER in seawater, its mass activity is about 4 times as high as that of Pt/C, demonstrating the great potential applications. By using Co single atom sites in Co SAs-ZIF-NC to isolate Pt, the obtained Pt@Co SAs-ZIF-NC catalyst, with uniform and highly dispersed Pt nanoparticles on porous Co SAs-ZIF-NC, presents highly efficient and stable dual-function catalysis toward oxygen reduction and hydrogen evolution reactions. • Single Co atom sites in Co SAs-ZIF-NC can isolate Pt and own strong interaction with Pt. • Obvious synergistic effect exists between Co single atom sites and Pt NPs in Pt@Co SAs-ZIF-NC catalysts. • With uniform and highly dispersed Pt NPs, Pt@Co SAs-ZIF-NC exhibits greatly enhanced ORR performance in acidic media. • In acidic media and seawater, high HER performance beyond commercial Pt catalysts is also obtained for the catalyst. • It provides a promising method for designing and constructing highly active and stable ultralow Pt-loaded catalysts.