Tuning the microphase behavior of carbon-precursor polymer blends with surfactant-like nanotubes: Toward catalyst support for water splitting

Abstract

• SWNTs modulate the interfacial tension between different polymers. • Fibrous structures consisting of thin nanofibers were created as catalyst supports. • Nanoparticulate binary-transition-metal-oxide were introduced as catalysts. • The resulting products showed good performance for both OER and HER. In this study, we demonstrated the ability of single-walled carbon nanotubes (SWNTs) to influence the microphase behavior of blended polymers by changing the interfacial tension, which facilitated control of the morphology and properties of the resulting carbonized products. SWNT-in-polymer blend nanofibers (SPNFs) were fabricated as a carbon-precursor with PMMA and PAN as the constituent polymers. The carbonized products of the SPNFs (CSPNFs) showed a unique morphology consisting of thin nanofibers with diameters less than 200 nm assembled into larger fibrous architectures. The surface area and pore volume of the CSPNFs increased proportionally with the amount of SWNTs added to the precursor. Representatively, CSPNF-3 had the highest surface area (∼600 m 2 g −1 ) and meso/macropore volumes (total ∼60 cm 3 g −1 ). The introduction of binary transition metal oxide (BTMO) phases into the CSPNFs as a support was also achieved with the aid of a stabilizer/dispersant polymer via dip coating followed by thermal reduction. The resulting C M SPNFs, where M indicates the introduced metal elements, were applied as electrocatalysts for water splitting. The C M SPNFs decorated with BTMO nanoparticles (diameter, 7–17 nm) exhibited higher electrocatalytic activities than the control prepared without SWNTs. The C M SPNF prepared with Ni and Fe precursors was found to be the best catalyst for either half-reaction (OER or HER), as well as in a symmetric two-electrode cell for both reactions. The demonstrated modulation of multi-polymer phase behavior by SWNTs can be applied to various combinations of precursor polymers and shows great promise for creating high-performance heterogeneous catalysts.