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

Nanocrystal co-existed highly dense isolated Pt single atom deposited on a three-dimensional hierarchical porous carbon (3D-HPC) matrix. The special structure of 3D-HPC with dense Pt single atom shows outstanding catalytic properties towards tri-iodide and oxygen reduction reactions (ORR) with low charge transfer resistance (Rct), higher current density, and half-wave potential. [Display omitted] •A three-dimensional hierarchical porous carbon was achieved from block copolymer.•Highly dense single atom Pt@3D-HPC co-existed with nanocrystal was obtained.•The Pt@3D-HPC shows outstanding catalytic properties towards IRR and ORR.•The Pt@3D-HPC also shows high efficiency in dye-sensitized solar cells.•This simple strategy to fabricate Pt@3D-HPC shows insights into a new approach. 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 (Rct) at the electrode/electrolyte interface with narrow peak-to-peak separation (△Epp) 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 (Eonset), half-wave potential (E1/2), 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