Molecular Assembled Electrocatalyst for Highly Selective CO Fixation to C Products.

In certain metalloenzymes, multimetal centers with appropriate primary/secondary coordination environments allow carbon-carbon coupling reactions to occur efficiently and with high selectivity. This same function is seldom realized in molecular electrocatalysts. Herein we synthesized rod-shaped nanocatalysts with multiple copper centers through the molecular assembly of a triphenylphosphine copper complex (CuPPh). The assembled molecular CuPPh catalyst demonstrated excellent electrochemical CO fixation performance in aqueous solution, yielding high-value C hydrocarbons (ethene) and oxygenates (ethanol) as the main products. Using density functional theory (DFT) calculations, X-ray absorption spectroscopy (XAS) and quasi- X-ray photoelectron spectroscopy (XPS), and reaction intermediate capture, we established that the excellent catalytic performance originated from the large number of double copper centers in the rod-shaped assemblies. Cu-Cu distances in the absence of CO were as long as 7.9 Å, decreasing substantially after binding CO molecules indicating dynamic and cooperative function. The double copper centers were shown to promote carbon-carbon coupling a CO transfer-coupling mechanism involving an oxalate (OOC-COO) intermediate, allowing the efficient production of C products. The assembled CuPPh nanorods showed high activity, excellent stability, and a high Faradaic efficiency (FE) to C products (65.4%), with performance comparable to state-of-the-art copper oxide-based catalysts. To our knowledge, our findings demonstrate that harnessing metalloenzyme-like properties in molecularly assembled catalysts can greatly improve the selectivity of CO2RR, promoting the rational design of improved CO2 reduction catalysts.