(726c) PdPt Alloy "Nanoclams" for CO2 Reduction in Tandem with Microbial Communities to Maximize Faradaic Efficiency to Value-Added Products

Improving the performance of cathodes for the electrochemical CO₂ reduction reaction (CO₂RR) will benefit from the discovery of new means to control catalysts activity and selectivity. This presentation focuses on the synthesis and systematic study of the CO₂ reduction activity of a novel quasi-2D PdPt bimetallic ‘nanoclam’ catalyst synthesized on carbon cloth electrodes via a pulsed electrodeposition technique. We also propose that the high activity of this catalyst at low overpotential is ideal for paring with biological systems to realize a hybrid system for CO₂ reduction.

The PdPt nanoclams have a unique tapered morphology that combines high surface area with exposure of numerous undercoordinated sites for CO₂ reduction with activity exceeding that of either Pd or Pt for CO₂ reduction to formate at 0.2 V vs RHE, which is a provocative result. In comparison with bulk Pd, PdPt, and Pt systems, we find that the interplay of multiple trends affect selectivity and activity:

1. Increasing Pt content shifts selectivity from formation of formate to hydrogen evolution in the bulk
2. Increasing Pt content increases overall activity and prevents catalyst deactivation while changing the energetics of hydride intercalation into PdPt
3. Nanostructured morphology of PdPt nanoclams increases selectivity to formate in PdPt nanoclams vs in bulk, planar PdPt.

Understanding the performance of PdPt for CO₂ reduction can lead to design principles that can inform the discovery of new classes of alloy catalyst with improved activity for CO₂ reduction.

In addition to this understanding, we report our results on the creation of a hybrid electrochemical-biological CO₂ reduction system in which formate and hydrogen are produced through electrochemical CO₂ reduction by PdPt nanoclams. These products are metabolized by methanogens in combination with CO₂ to yield ~100% faradaic efficiency to methane. Going forward, the integration of microbial communities with these nanostructured PdPt catalysts has the potential to combine the best-of-both-worlds from electrochemical and biological systems to achieve a regenerative catalytic system with high-selectivity, high activity, and low overpotential.