Sorbent Mediated Electrocatalytic Reduction of Dilute CO to Methane.

Efficient CO utilization is a critical component of closing the anthropogenic carbon cycle. Most studies have focused on the use of pure streams of CO. However, CO is generally available only in dilute streams, which requires capture by sorbents followed by energy-intensive regeneration to release concentrated CO. Direct utilization of sorbed-CO avoids the costly regeneration step, and the sorbent-CO interaction can kinetically activate CO to tune its reactivity toward products that could otherwise be inaccessible with direct CO reduction. We demonstrate that an -heterocyclic carbene, 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (DPIy), quantitatively reacts with CO from dilute streams (0.04 and 10%) to form the sorbent-CO substrate 1,3-bis(2,6-diisopropylphenyl)imidazolium-2-carboxylate (DPICx). Electrocatalyst iron tetraphenylporphyrin chloride (Fe(TPP)Cl) typically reduces CO to CO; however, with DPICx as the substrate, the eight-electron reduced product methane (CH) is produced with a high Faradaic efficiency (>85%) and regeneration of the sorbent DPIy. In addition to the overall energy and capital advantages of integrated CO capture and conversion, this result illustrates how sorbents can serve a dual purpose for both CO capture and chemical auxiliary purposes to access unique products. CO has a spectrum of reactivity with different types of sorbents; thus, these studies demonstrate how sorbent-CO interactions can be leveraged for integrated capture and utilization platforms to access a wider range of CO-derived products.