Mangrove Root-Inspired Carbon Nanotube Film for Micro-Direct Methanol Fuel Cells

The functional microporous layer, acting as a mass-transfer control medium with a rational structure and surface morphology as well as high electrical conductivity, significantly affects the performance of micro-direct methanol fuel cells (μDMFCs). Bioinspired by the architecture and multi-functional properties of mangrove roots, this study develops a simple and versatile strategy based on magnetron sputtering and chemical vapor deposition to fabricate a mangrove root-inspired carbon nanotube film (MR-CNTF) as the functional interface in μDMFCs. It has features such as ultralightweight, high porosity, and good electrical conductivity. During the synthesis process, an apex-growth model of CNTF is identified. The results indicate that the MR-CNTF used as a cathodic microporous layer can remarkably facilitate the oxygen transport and water management. Because of its multi-functional structure and excellent material characteristics, the passive μDMFC displays a peak power density of 14.9 mW cm^-2 at 68 mA cm^-2. This value is 88.6% higher than the highest power density of the one based on a carbon nanotube array (7.9 mW cm^-2) and 45% higher than that of the conventional carbon black (10.7 mW cm^-2). We believe that this novel material with its multi-functional structure illuminates a promising application for fuel cells and other energy storage and conversion devices.