The ability to convert H2O, CO2 and N2 into fuels using renewable energy inputs could in principle provide a viable alternative to the current dominance of fossil fuels. This prospect faces great technical challenges, the foremost of which is the lack of efficient and robust electrocatalysts for the various multi-electron processes that fuel synthesis demands. We are working to address this deficiency for the two most challenging reactions: CO2 reduction and N2 reduction.
We have developed a new class of catalysts called “oxide-derived” metal nanoparticles, which are prepared by electrochemically reducing a metal oxide precursor. The process of metal oxide reduction kinetically traps metastable nanoparticle structures that exhibit catalytic properties not found in nanoparticles prepared by conventional syntheses. Oxide-derived nanoparticles exhibit unprecedented efficiency for CO2 reduction at potentials close to the thermodynamic minimum, enabling energetically efficient reductions under ambient conditions. The ultimate goals of this research are to develop catalyst design principles that are applicable to multiple materials and to provide viable candidate electrode materials for practical devices.
Current strategies for controlling selectivity in chemical reactions rely principally on molecular recognition elements. As an alternative, we are developing catalysts and catalyst–surface interfaces that exploit non-bonding electrostatic interactions to control selectivity. We are particularly interested in using externally-applied interfacial electric fields to modulate the activation barriers of competing reactive pathways. We have designed a reaction cell wherein the charge density at an electrode surface coated with an insulating layer can be controlled by a voltage source. By confining catalysts to this interface, we can externally modulate the local electrostatic environment in which a reaction takes place.
We have shown that local charge density can change the selectivity of reactions catalyzed by both solid-state and molecular catalysts. Additionally, we are developing homogeneous catalysts with strategically placed ionic functionalities to maximize the influence of ion pairing and solvent effects on selectivity. The ultimate goals of these efforts are to link selectivity to readily adjustable external parameters and to address selectivity challenges that are particularly difficult for traditional approaches.