Holey Bismuth for Selective Electrochmical CO₂ Reduction

Because of the consumption of fossil fuel, CO2 emission, a product of burning fossil fuel, causes the global warming. Electrochemical CO2 reduction reaction (eCO2RR) provides a solution that allows to reduce the carbon emission and produce useful products. Among those CO2 reduction products, formic acid is one of the most attractive candidates because it has higher volumetric capacity of H2 (53 g H2/L) and can release H2 by catalyst under room temperature, which makes it a promising energy carrier.[1] Also, it is feasible to transport since it is nonflammable and stable under room temperature. Among the materials for eCO2RR, bismuth has better selectivity toward formate production (Faraday efficiency > 80%).[2] However, production rate, partial current density toward formate, of those catalyst remained low. One of the approach to boost the production rate is to increase the surface area of catalyst. By creating the porous structure, surface area of catalyst will be increased and thus enhances the production rate of formate. In this work, we successfully synthesized sponge-liked bismuth by chemical vapor deposition (CVD) method for eCO2RR. As results, it shows an excellent current density (28 mA/cm2) and faraday efficiency toward formate (95%) in moderate applied potential -1.05 V (vs. reversible hydrogen electrode (RHE)) under low catalyst loading. Furthermore, Comparing to electroplating bismuth, sponge-liked bismuth have double current density under same electroactive surface area. [1] Eppinger, J. and K.W. Huang, Formic Acid as a Hydrogen Energy Carrier . Acs Energy Letters, 2017. 2(1): p. 188-195. [2] Larrazabal, G.O., A.J. Martin, and J. Perez-Ramirez, Building Blocks for High Performance in Electrocatalytic CO2 Reduction: Materials, Optimization Strategies, and Device Engineering. J Phys Chem Lett, 2017. 8(16): p. 3933-3944.