Vertically Aligned Multiwalled Carbon Nanotube/Cu Catalysts for CO2 Electroreduction

Enhancing the selectivity of hydrocarbon products remains a key challenge to achieving artificial energy sustainability via closing the carbon cycle. While copper-based electrodes uniquely yield hydrocarbon products, the improvement of their product selectivity through physical morphology regulation shows great potential and requires further investigation. Here, we show the distinct morphological influences of the Cu electrode on the reaction selectivity. We synthesize binder-free, vertically aligned, nanoid forest-like copper electrocatalysts for superior improved methane conversion selectivity with respect to planar Cu. These Cu nanocomposites are fabricated through the conformal coating of vertically aligned multiwalled carbon nanotube array electrodes, which have matured to a cost-effective and scalable technology over the past two decades. Simulations reveal that carbon intermediates and protons can be confined in the gaps of the nanoid copper forest, which are formed in situ and in turn cover the catalytic sites and facilitate the simultaneous transfer of coupled electrons and protons. Such forest-like antenna morphology benefits from a threefold improvement of the CO2 electroreduction performance through a decreased reaction onset potential, an increased current density, and enhanced hydrocarbon selectivity.