Facile Decoration of Platinum Nanoparticles on Carbon-Nitride Nanotubes via Microwave-Assisted Chemical Reduction and Their Optimization for Field-Emission Application

This study reports a simple, efficient method of using Pt nanoparticles to decorate CNx nanotubes with controllable particle size and population density. CNx nanotubes, synthesized by the chemical vapor deposition of an imidazole-ferrocene mixture at 750 °C, were dispersed in 2-(2-methoxyethoxy)-ethanol solvent together with H 2 PtCl 6 . The reduction of Pt(IV) to Pt(0) was achieved with NaBH 4 and microwave irradiation, separately. The NaBH 4 -mediated reduction process results in Pt nanoparticles of small size decorating the CNx surface with low density. However, microwave-assisted chemical reduction leads to larger nanoparticles with a high population density. It is observed that Pt-anchoring on the CNx strands is mainly governed by pyridinic-N (pN) units. The XPS peak intensities of Pt(II) and Pt(IV) are very low when Pt nanoparticles are grown via a microwave-irradiation process, as compared to the NaBH 4 reduction process. This suggests that NaBH 4 treatment leads to the incomplete reduction of Pt ions. In contrast, microwave irradiation not only offers complete Pt reduction but also enables control of the particle size and density as a function of the irradiation time. Moreover, the field-emission (FE) performance is found to increase with increasing irradiation time. The field enhancement factor of the longest microwave-irradiated (110 s) sample increased 5-fold as compared to that of the bare CNx sample. This is the first experimental evidence of the FE enhancement of platinum-decorated CNx nanotubes.