Porous Wood Monoliths Decorated with Platinum Nano-Urchins as Catalysts for Underwater Micro-Vehicle Propulsion via H₂O₂ Decomposition

Porous carbon is becoming an important and promising high-surface-area scaffold material for various energy-based applications including catalysis. Here we demonstrate the growth of urchin-like platinum nanoparticles (PtNPs) on carbon monoliths derived from basswood that work as catalysts for micro underwater vehicle (MUV) propulsion via H2O2 decomposition. The carbon monoliths were constructed of natural basswood that was carbonized in argon (Ar) and subjected to a subsequent CO2 activation process that rendered the material into a hardened 3D porous activated carbonized wood (ACW) with inner channel voids measuring 10–70 μm in diameter. The PtNP nano-urchins (500 nm or less in total diameter, with individual nanospikes measuring 3–5 nm in diameter) form on the ACW via a facile electroless and template-free chemical deposition approach that utilizes the reduction of chloroplatinic acid. The developed PtNP–ACW hybrid material exhibited higher catalytic efficiency as compared to previously reported platinum (Pt) catalysts with a low activation energy of 18.9 ± 2.5 kJ mol–1 for H2O2 decomposition. The catalyst also proved useful in an important energy application by its ability to rapidly decompose H2O2 fuel and generate O2 gas for propulsion of a 3D printed MUV prototype. The PtNP–ACW catalysts weighing only 0.14 g generated a propulsion thrust of 230 mN, which is sufficient to power MUVs. The natural wood derived carbon scaffolds significantly reduce the overall cost as compared to other carbon-based catalysts such as carbon nanotubes or graphene without reducing catalytic efficiency. Hence, such catalysts act as a stepping stone for potential low cost and sustainable power for burst thrust operation of MUVs.