Regulating the Product Distribution of CO Reduction by the Atomic-Level Structural Modification of the Cu Electrode Surface

Abstract

Cu catalyzes the electrochemical reduction of CO_2 or CO to an assortment of products, a behavior that is a detriment when only one reduced compound is desired. The present article provides an example in which, through the atomic-level control of the structure of the Cu electrode surface, the yield distribution is regulated to generate only one product. The reaction investigated was the preferential reduction of CO to C_2H_5OH on Cu at a low overpotential in alkaline solution. Experimental measurements combined electrochemical scanning tunneling microscopy (ECSTM) and differential electrochemical mass spectrometry (DEMS). An atomically ordered Cu(100) surface, prepared from either a single crystal or by Cu(pc)-to-Cu(100) reconstruction, did not produce ethanol. When the surfaces were subjected to monolayer-limited Cu↔Cu_2O cycles, only the reconstructed surface underwent an additional structural transformation that spawned the selective production of ethanol at a potential 645 mV lower than that which generates multiple products. Quasi-operando ECSTM indicated transformation to an ordered stepped surface, Cu(S) − [3(100) × (111)], or Cu(511). The non-selective, multiple-product Cu-catalyzed reduction of CO had thus been regulated to yield only one liquid fuel by an atomic-level structural modification of the electrode surface.