Compared to traditional metal nanoparticle catalysts, sub-nanometer and single atom metal catalysts (atomic catalysts) possess enhanced catalytic activity. Beyond metal-based atomic catalysts, we have recently shown metal free atomic catalysts of nitrogen (N) doped carbon sp2 sheets (graphene) as possible CO2 reduction catalysts. We designed N-incorporated carbon nanostructures (N-doped carbon nanotubes and N-doped graphene) for selective and efficient electro-reduction of CO2 into CO with high efficiency (~80%) and at low overpotential.1-3 We further demonstrated that the N-doped carbon materials can be atomically engineered to achieve the yield of high order (C2 and C3) products. when enriching the N-doping at the edge of carbon nanostructures, the N-doped graphene quantum dots (NGQDs, thickness ~ 1nm and diameter ~ 2 nm) exhibit exceptional activity towards formation of C2 products (C2H4 and C2H5OH) with high Faradaic efficiency of 40%, and the current density is enhanced to the order of magnitude of 100 mA/cm2 at this potentialOc.4 This is for the first time the metal-free electrocatalyst has been discovered to steer the CO2reduction to produce C2 hydrocarbons and oxygenantes at a relatively high yield comparable to those obtained with copper nanoparticle-based electrocatalysts.
1. J. Wu et al. Achieving highly efficient, selective and stable CO2 reduction on nitrogen doped carbon nanotubes. ACS nano 9, 5364–5371 (2015).
2. P. P. Sharma et al. Nitrogen-doped carbon nanotube arrays for high-efficiency electrochemical reduction of CO2. Angewandte Chemie International Edition 54, 13701–13705 (2015).
3. J. Wu et al. Incorporation of nitrogen defects for efficient reduction of CO2 via two-electron pathway on three-dimensional graphene foam. Nano Letter 16, 466-470 (2016).
4. J. Wu et al. A metal free electrocatalyst for carbon dioxide reduction to multi-carbon hydrocarbons and oxygenates. Nature Communications 7,13869 (2016)