Self-assembly of Pt-based truncated octahedral crystals into metal-frameworks towards enhanced electrocatalytic activity

Abstract

Self-assembly of Pt-based truncated octahedral crystals into frameworks has been demonstrated in this paper by suitably adjusting the reactant concentrations and temperature. This approach allows for control of Pt or Pt-based nano-crystals with subnanometer-size as building blocks for metal-frameworks (MFs): sub-micron porous tubes (SMPBs) and mesh (M). Both the Pt-based MFs exhibit enhanced activity and better stability for the oxygen reduction reaction (ORR) and methanol-oxidation reaction (MOR) than PtMFs. The mass activity (MA) of the Pt₄Cu-SMPBs (0.619 A mg⁻¹@0.9 V) exhibited 5.12 times enhancement over the commercial Pt/C (0.121 A mg⁻¹@0.9 V) catalyst towards the ORR and the value is well beyond the U.S. Department of Energy's 2017 target (0.44 A mg_Pt⁻¹ @0.9 V). After 8000 cycles of accelerated durability test, the MA of the Pt₄Cu-SMPBs (0.411 A mg⁻¹@0.9 V) was still greater than the values of the Pt/C. These metal-framework materials provide a new direction to obtain highly open nanostructures which would readily improve their catalytic properties in both activity and durability while reducing their loading.