(357c) Mass Transport Optimization in Direct Formic Acid Fuel Cell Catalyst Layer Via Pore-Former Templating

To meet the ever-rising demand for portable power sources, batteries have become a vital part in mobile electronics such as cell phones and laptops. However, the efficiency of batteries is compromised due to exponential degradation over time, lengthy recharging times, and limited charge capacity. Direct formic acid fuel cells (DFAFC) present an alternative to batteries, due to their near instantaneous re-fueling times, higher efficiency, and 24/7 operation capabilities. The source of fuel (formic acid) is sustainable via renewable sources. [1] However, two-phase flow in conjunction with the small pore size between anode catalyst agglomerates (~20 nm) restricts the cell’s efficiency. To improve the mass transport liquid reactants (formic acid) and gaseous products (carbon dioxide), a pore-former is integrated into the anode catalyst layer during fabrication and subsequently removed. The additional templated porosity enhances the two-phase mass transport in and out of the anode catalyst layer.

In 2012, pore-former (lithium carbonate, LiCO₃) was incorporated and removed from the anode catalyst layer forming ~10 μm pores. [2] Peaking at 17.5 wt% pore-former addition, the increase in porosity resulted in a reduction of the formic acid electrooxidation charge transfer. The increased porosity the disconnection between catalyst agglomerated and reduced the connected electrochemical surface area.

Previous work has been done with the addition of a smaller pore-former, MgO (~50 nm). [3] The intent of the smaller pore-former is to increase the porosity of the anode catalyst layer while retaining the connectivity of the agglomerates. The addition of 25 wt% pore-former increased the electrochemical surface area and cell performance by 293% and 86%, respectfully, compared to an anode catalyst layer with no pore-former. The present work aims study more variations in the wt% of pore-former (0-30 wt%), the effect of pore-former wt% on catalyst ink viscosity, and the effect of catalyst ink sonication with pore-former.

1. Ma, Z., Legrand, U., Pahija, E., Tavares, R.J., and Boffito, C.D., From CO₂ to Formic Acid Fuel Cells. 2021, 60(2), 803-815.
2. Bauskar, A.S. and Rice, C.A., Impact of Anode Catalyst Layer Porosity on the Performance of a Direct Formic Acid Fuel Cell. 2012, 62, 36-41.
3. Lam, S., Bixby, M.M., and Rice, C.A., Optimization of Mass Transport within Direct Formic Acid Fuel Cell Catalyst Layer via Pore Formers. 2020, 98, 355.