Hierarchically porous, biaxially woven carbon nanotube sheet arrays for next-generation anion-exchange membrane water electrolyzers

Abstract

The commercialization of anion-exchange membrane water electrolysis (AEMWE) requires the development of a highly efficient cathode. Here, we propose a novel cathode design based on a hierarchically porous, biaxially woven carbon nanotube sheet (CNTS) array, which increases the total surface area of the catalyst and improves the transport of ions, electrons, reactants, and products. In this design, where metals are supported on the CNTS (M_CNTS), catalyst nanoparticles for catalyzing the hydrogen evolution reaction (HER), i.e., non-noble or noble metal catalysts, are well dispersed on the biaxially woven CNTS substrate with square-shaped pores. Both types of catalysts (i.e., NiFeO_x and Pt) enabled the M_CNTS electrode to exceed the AEMWE performance compared to the conventional electrode with densely packed nanoparticles. In particular, the Pt catalyst yielded a performance (4.0 A cm⁻² at 1.9 V) that is the highest to date. This is attributed to the three-dimensional porous structure of the M_CNTS design. Because the M_CNTS design performed reliably during AEMWE, it is an alternative to conventional cathodes.