Dual atom catalysts for rapid electrochemical reduction of CO to ethylene

Abstract

Strong CO adsorption and facile CO dimerization are the key challenges in electrochemical CO₂ reduction towards multi-carbon (C₂₊) products. We recently showed that CoPc immobilized on a single-walled carbon nanotube can selectively reduce CO₂ to methanol. This is enabled through molecular strain, which dramatically improves the CO adsorption energy to CoPc, which in turn facilitates methanol formation. We now examine the extended Phthalocyanine (Pc_Ex) dual atom catalyst (DAC), which is intrinsically strained and contains two catalyst centers, making it a candidate for reducing CO to C₂₊ products. Using Quantum Mechanics (QM), we screened 20 elements embedded in the Pc_Ex, seeking catalysts with weak hydrogen binding, strong CO binding, and facile CO dimerization. We identified Fe, Ru, Co, and Ir as the best performers and subsequently evaluated the entire CO to C₂H₄ mechanism (9 steps) using each of these elements as catalysts. In terms of limiting potential and overall exergonicity, we identified CoPc_Ex as the best catalyst, followed by IrPc_Ex. We then examined the full CO to C₂H₄ mechanism on the bimetallic IrCoPc_Ex catalyst using grand canonical QM to obtain the reaction energetics as a function of applied potential. We conclude that the bimetallic IrCoPc_Ex is most promising for efficiently converting CO to ethylene.

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