Electroreduction of CO2 on bismuth nanoparticles in seawater

The electrochemical reduction of CO2 to formate was investigated in seawater as an alternative electrolyte to the bicarbonate buffer commonly used. Bismuth nanoparticles were prepared by pulsed laser ablation in liquids in ethanol, avoiding the use of toxic reagents or solvents. TEM analysis showed the nanoparticles were monodisperse and had an average number weighted diameter of 13 +/- 5 nm. XRD showed that the nanoparticles were metallic which could suggest the presence of a carbon shell on the nanoparticles. However, this potential carbon shell does not appear to interfere with the electrocatalytic activity of the nanoparticles. A stepwise optimization of the catalyst weight fraction, Nafion (R) content, and loading showed that the best performances were achieved for 90% wt. bismuth nanoparticles on carbon, at a loading of 0.25 mg cm(-2) and with 0.24% wt. Nafion (R). The electrolysis in seawater showed similar or improved results both in terms of onset potential (- 1 V vs Ag/AgCl) selectivity (81 +/- 4%) and activity (- 47 +/- 11 mA cm(-2)) when compared to the reference bicarbonate buffer, demonstrating that seawater is an abundant, affordable alternative to the current buffer.