We develop selective and robust catalysts that electrochemically convert carbon dioxide (CO2) into sustainable chemical feedstocks and could ultimately be coupled to the recycling of environmental CO2. The catalysts employed are transition metal phosphides and their doped derivatives that form distinct crystalline structure types, enabling selection of chemical reactivity towards desired products including high molecular weight solid polymers. Selecting the catalyst’s elemental composition and crystal structure allows for tuning of the chemical, physical, and electrical properties to achieve the best match with desired product and application.
Transition metal phosphides are efficient hydrogen evolution catalysts due to their ability to abstract protons from water and transfer electrons to them, forming adsorbed hydrides. Since CO2 reduction also requires multiple transfers of adsorbed hydrogen and electrons, these catalysts are also effective for the reduction of CO2. Additionally, these catalysts bind CO2 relatively strongly, allowing for the formation of C3, C4 and Cn products at ambient conditions and aqueous solution. It is also our belief that when utilizing iron and nickel phosphides, the reaction proceeds through hydride transfer, and therefore carbon monoxide is not an intermediate. This opens up a new reaction pathway with minimal overpotential requirements.
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