CO₂ holds the potential to a significant source of renewable carbon. Previous studies have shown that it can be converted to CO, CH₄, HCOOH, CH₃OH and other higher order hydrocarbons suitable as fuels or chemical intermediates. The electrochemical approach holds the advantage in using renewable electric source (wind, solar and tide). Extensive experimental and theoretical studies have been done on pure metals (such as Au, Ag, Cu, etc.)^{1, 2} range from bulk to nano scale³, Cu⁴ appear to be the only catalyst that is capable of perform hydrogenation to yield hydrocarbon liquid products at the expense of single product selectivity and overpotential. Density function theory based simulation suggest the unique binding energies of CO* and COH* are the key for copper to perform the hydrogenation. ⁵

We took the inspiration from nature’s enzyme chemistry⁶ which manipulate metal nanoclusters with ligands in photosynthesis, explored the possibility using engineered metal-ligand electrocatalyst to yield the hydrocarbon liquid products. Our previous work has shown that thiolate ligands can facilitate reduction and hydrogenation at neutral to mildly acidic pKa. Suitable ligands can significantly enhance the yield of CO or HCOOH (usually trace on Au) production. We are taking a step further by depositing strong CO binding metal nanoparticles on to salinized semiconductor substrate with proton donor group to create metal-ligand interfaces. We have observed enhanced CH₃OH production in such systems. The engineered metal-ligand interface thus appear to be a highly promising method to promote hydrogenation routes in CO₂ electrochemical reduction.

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