Coupling palladium nanocrystals over D‑phenylalanine-functionalized carbon nanotubes as an advanced electrocatalyst for hydrogen evolution and ethanol oxidation

Abstract

The D-phenylalanine-functionalized carbon nanotubes coupled with Pd nanocrystals (denoted as Pd/CNTs-DPHE) was designed and implemented as an advanced electrocatalyst for hydrogen evolution (HER) and ethanol oxidation (EOR). Primarily, the D-phenylalanine containing carboxyl and amino groups was covalently and uniformly grafted on the surface of CNTs by the diazo-reaction. This protocol can enable the controllability of the DPHE contents by adjusting the ratio of D-4-amino-phenylalanine to CNTs under facile reaction conditions. And then, the Pd nanocrystals with small size distribution were anchored on the CNTs-DPHE by a simple wet chemical growth method. Adequate carboxyl and amino groups in the obtained-electrocatalyst not only can act as anchor sites for Pd nanocrystals with small size and even dispersion, but also can affect the electronic structure of Pd and the proton conductivity of the electrocatalyst, due to the strong interactions between Pd and the functional groups (amino and carboxyl groups). Consequently, the Pd/CNTs-DPHE exhibited advanced electrocatalytic behavior for HER and EOR, including accelerated kinetics, improved electrocatalytic activity, enhanced long-term stability and boosted anti-poisoning capability. Moreover, the electrocatalytic HER and EOR behavior of the Pd/CNTs-DPHE also depends on the contents of DPHE and the optimal mass ratio of D-4-amino-phenylalanine to CNTs is 5:1 for synthesizing the perfect supporting material. Furthermore, the CNTs-DPHE probably serves as high-performance support for other metal electrocatalyst and this work will provide a new access for rational design of functional carbonaceous materials.