A key challenge in heterogeneous catalysis has been developing technologies that can selectively convert CO2 or CO into short-chain multi-carbon oxygenates. Here, I will show how to improve selectivity to multi-carbon oxygenates by rationally controlling a variety of properties that are intrinsic and extrinsic to the catalyst. First, I will discuss how extrinsic properties such as the electrochemical potential and electrolyte pH impact reactivity on polycrystalline Cu electrodes. By comparing CO and CO2 reduction from similar reactors, we demonstrate that alkaline reaction conditions increase the energy efficiency towards multi-carbon products. Furthermore, we reveal selectivity trends that are common to both CO and CO2 reduction, indicating both the production of oxygenates and the growth of longer carbon chains are favored at lower overpotentials. Next, I will show how proper control of these extrinsic properties combined with increasing the electrode surface area of polycrystalline Cu leads to high selectivity for multi-carbon oxygenates. We demonstrate that by increasing the electrode surface area, nearly 100% selectivity for CO electroreduction to liquid-phase products is achieved at a very low overpotential of ~200 mV, from a concomitant suppression of the competing hydrogen evolution reaction. Furthermore, we reveal the generalizability of this surface area effect by using a variety of methods to synthesize polycrystalline Cu electrodes of many different morphologies and roughness factors, and comparing their electrocatalytic performance. Finally, I will show how combining all of these design principles with controlling the surface composition, an intrinsic property of the catalyst, leads to improved selectivity for a single multi-carbon oxygenate. Under alkaline reaction conditions, we observed high selectivity for CO reduction to acetaldehyde on CuAg bimetalic electrodes at low overpotentials, reaching a maximum total Faradaic efficiency of &gt;70% and selectivity of &gt;90% on a carbon basis.

CO & CO2 reduction: Mechanistic understanding of selectivity and activity to enable catalyst discovery

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.