Nanocrystal co-existed highly dense atomically disperse Pt@3D-hierarchical porous carbon electrocatalysts for tri-iodide and oxygen reduction reactions

The fabrication of highly dense atomically dispersed platinum (Pt) on a carbon matrix increases the catalytic sites and is one of the ways to utilize Pt to make inexpensive and highly efficient electrocatalysts. We have employed a three-dimensional hierarchical porous carbon (3D-HPC) substrate and nanocrystal co-existed highly dense Pt single atoms deposited by the incipient wetness impregnation method. The special structure of the 3D-HPC substrate favors the homogeneous dispersion of Pt all over the 3D-HPC, leading to nanocrystal co-existed highly dense atomically disperse Pt@3D-HPC. The as-prepared Pt@3D-HPC shows outstanding catalytic properties towards tri-iodide and oxygen reduction reactions (ORR). The Pt@3D-HPC electrode shows lower charge transfer resistance (R_ct) at the electrode/electrolyte interface with narrow peak-to-peak separation (△E_pp) and higher peak current density during the tri-iodide reduction reaction (IRR). The DSSC fabricated with a Pt@3D-HPC electrode shows improved performance compared to the reference Pt counter electrode (CE). Furthermore, CV and LSV demonstrate the better catalytic activity of Pt@3D-HPC towards ORR, with higher onset potential (E_onset)_, half-wave potential (E_1/2), and current density (j) compared to the reference 20% Pt/C electrode. Furthermore, impressive mass activity was observed by the Pt@3D-HPC catalyst compared to 20% Pt/C and other recently reported single atom-based catalysts. The Pt@3D-HPC catalyst also shows improved stability towards IRR and ORR. This simple strategy to fabricate nanocrystal co-existed highly disperse Pt@3D-HPC catalysts with outstanding electrocatalytic performance and stability paves the way for its practical application and provides insights into a new approach to the design of electrocatalysts applicable to energy-related devices.