Controlling the chemical environment around electrocatalysts through polymer encapsulation is an important strategy for increasing catalytic activity and selectivity for the CO2 reduction reaction (CO2RR). In particular, the encapsulating polymer surrounding a molecular catalyst can modulate the coordination environment of the catalyst active site in the catalyst’s primary coordination sphere, stabilize catalytic intermediates through H-bonding in the catalyst’s secondary coordination sphere, and control substrate and proton delivery to the catalyst through facilitated transport in the catalyst’s outer coordination sphere. Modifying each of these coordination spheres can have profound impacts on the activity, reaction selectivity, and mechanism of CO2 reduction by the encapsulated molecular electrocatalysts. Here, we present some our recent studies exploring the effect of each coordination sphere on the CO2RR by polyvinylpyridine-encapsulated cobalt phthalocyanine (CoPc). In particular, we show that proton transport through the polyvinylpyridine polymer to the catalyst active site occurs via a proton-relay mechanism (rather than simple diffusion). The nature of the proton transport through the polymer has important implications for both catalyst activity and selectivity. In addition, we show that axial coordination to CoPc changes the rate determining step in the CO2RR mechanism resulting in an increase in electrocatalytic activity. The extent of the activity increase is related to the sigma-donor strength of the coordinating moiety. These findings demonstrate the viability of polymer-encapsulation as a means to design new active electrocatalytic systems based on molecular electrocatalysts for selective CO2 reduction.

Using polymer encapsulation to influence the mechanism, activity, and selectivity of electrocatalytic CO2 reduction by molecular catalysts

2019 Fall National Meeting

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