Abstract
Electroreduction of carbon dioxide into higher-energy liquid fuels and chemicals is a promising but challenging renewable energy conversion technology. Among the electrocatalysts screened so far for carbon dioxide reduction, which includes metals, alloys, organometallics, layered materials and carbon nanostructures, only copper exhibits selectivity towards formation of hydrocarbons and multi-carbon oxygenates at fairly high efficiencies, whereas most others favour production of carbon monoxide or formate. Here we report that nanometre-size N-doped graphene quantum dots (NGQDs) catalyse the electrochemical reduction of carbon dioxide into multi-carbon hydrocarbons and oxygenates at high Faradaic efficiencies, high current densities and low overpotentials. The NGQDs show a high total Faradaic efficiency of carbon dioxide reduction of up to 90%, with selectivity for ethylene and ethanol conversions reaching 45%. The C2 and C3 product distribution and production rate for NGQD-catalysed carbon dioxide reduction is comparable to those obtained with copper nanoparticle-based electrocatalysts.
Highlights
Electroreduction of carbon dioxide into higher-energy liquid fuels and chemicals is a promising but challenging renewable energy conversion technology
To expose the edge sites and increase their density in carbon nanostructures while simultaneously introducing non-metal heteroatom dopants at the edge locations, we intended to synthesize N-doped graphene quantum dots (NGQDs) through exfoliating and cutting graphene oxide (GO) precursor, and in-situ N doping in the dimethylformamide (DMF) solvent at elevated temperature and pressure[20]
We do not have a large quantity sample base to analyse the percentage of NGQDs with zigzag edges over armchair edges, but the exigence of NGQDs with armchair edges could not be excluded in our sample
Summary
Electroreduction of carbon dioxide into higher-energy liquid fuels and chemicals is a promising but challenging renewable energy conversion technology. Among the electrocatalysts screened so far for carbon dioxide reduction, which includes metals, alloys, organometallics, layered materials and carbon nanostructures, only copper exhibits selectivity towards formation of hydrocarbons and multi-carbon oxygenates at fairly high efficiencies, whereas most others favour production of carbon monoxide or formate. We report that nanometre-size N-doped graphene quantum dots (NGQDs) catalyse the electrochemical reduction of carbon dioxide into multi-carbon hydrocarbons and oxygenates at high Faradaic efficiencies, high current densities and low overpotentials. The resulting catalyst, N-doped graphene quantum dots (NGQDs), has substantially enriched density of N-doping defects at edge sites These NGQDs exhibit high activity towards the electrochemical reduction of CO2 as evidenced by high reduction current densities at low overpotentials and, more importantly, they preferentially produce multi-carbon hydrocarbons and oxygenates, especially the C2 products ethylene (C2H4) and ethanol (C2H5OH) at FEs comparable to those obtained using Cu nanoparticle-based catalysts
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