Kwan-Woo Nam

Cotton-templated hierarchical porous structures for high power lithium rechargeable batteries

High power full-cells of LiNi0.5Mn1.5O4–Li4Ti5O12 are demonstrated by engaging a scalable cotton-templated synthetic process. The cotton-templated method produces hierarchical structures in which primary particles in the range of 100–300 nm form three-dimensional porous secondary structures for both electrodes. While the primary particles in the smaller scales facilitate efficient electronic/ionic diffusion for high rate performance, the three-dimensional porous secondary structures remain stable during cycling for excellent cycle life. The synthetic method introduced herein is simple and universal, and should thus be applicable to other battery materials requiring high power performance.

Perfluorosulfonic acid-functionalized Pt/graphene as a high-performance oxygen reduction reaction catalyst for proton exchange membrane fuel cells

Platinum nanoparticles (Pt NPs) on carbon black (CB) have been used as catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells for a while. However, this catalyst has suffered from aggregation and dissolution of Pt NPs as well as CB dissolution. In this study, we resolve those issues by developing perfluorosulfonic acid (PFSA)-functionalized Pt/graphene as a high-performance ORR catalyst. The noncovalently bonded PFSA remarkably decreases the dissolution and aggregation of Pt NPs. Moreover, unlike typical NP functionalization with other capping agents, PFSA is a proton conductor and thus efficiently develops a triple-phase boundary. These advantageous features are reflected in the improved cell performance in electrochemical active surface area, catalytic activity, and long-term durability, compared to those of the commercial Pt/C catalysts and graphene-based catalysts with no such treatment.