(600e) Oxide-Derived Tin Microspheres for Efficient CO2 Electroreduction to Formic Acid

Nguyen-Phan, T. D. - Presenter, National Energy Technology Laboratory
Kauffman, D. R., National Energy Technology Laboratory
Rational design and engineering of electrocatalysts for electrochemical CO2 reduction (CO2RR) is crucial to effectively, selectively converting CO2 into carbon-neutral chemicals and fuels. In this work, we have developed low-cost hierarchical tin oxide microsphere electrocatalysts to boost the production of formic acid. Three-dimensional (3D) SnO2 spheres constructed from small crystalline nanoparticles exhibit high Faradaic efficiencies (70-80%) and high selectivities (77-90%) toward formic acid in a wide potential window of -0.9 V to -1.3 V vs. the reversible hydrogen electrode (RHE) at total current densities of 30-100 mA/cm2. A peak 80.3% Faradaic efficiency is obtained at -1.2 V vs. RHE with superior HCOOH partial current density of 50.4 mA/cm2. Such unique 3D spherical catalysts outperform non-spherical nanoparticles and commercially available SnO2 benchmarking catalysts due to special hierarchical porous structure, enlarged surface area, larger number of electrochemically active sites, and strongly suppressed H2 evolution. The spherical oxide-derived Sn catalysts are highly stable up to 36 hours over many start/stop cycles at -1.2 V vs. RHE, preserving long-term partial current density of 45 mA/cm2 and 90% selectivity for formic acid. Our results may provide more guidelines for the introduction of hierarchical porosity into CO2RR electrocatalysts for large-scale applications.