Electrochemically scrambled nanocrystals are catalytically active for CO ₂ -to-multicarbons

Abstract

Promotion of C–C bonds is one of the key fundamental questions in the field of CO2 electroreduction. Much progress has occurred in developing bulk-derived Cu-based electrodes for CO2-to-multicarbons (CO2-to-C2+), especially in the widely studied class of high-surface-area “oxide-derived” copper. However, fundamental understanding into the structural characteristics responsible for efficient C–C formation is restricted by the intrinsic activity of these catalysts often being comparable to polycrystalline copper foil. By closely probing a Cu nanoparticle (NP) ensemble catalyst active for CO2-to-C2+, we show that bias-induced rapid fusion or “electrochemical scrambling” of Cu NPs creates disordered structures intrinsically active for low overpotential C2+ formation, exhibiting around sevenfold enhancement in C2+ turnover over crystalline Cu. Integrating ex situ, passivated ex situ, and in situ analyses reveals that the scrambled state exhibits several structural signatures: a distinct transition to single-crystal Cu2O cubes upon air exposure, low crystallinity upon passivation, and high mobility under bias. These findings suggest that disordered copper structures facilitate C–C bond formation from CO2 and that electrochemical nanocrystal scrambling is an avenue toward creating such catalysts.

Morphology and mechanism of highly selective Cu(II) oxide nanosheet catalysts for carbon dioxide electroreduction

“…To follow the evolution in chemical state and morphology of electrocatalysts under stationary electrode potential conditions, operando X-ray-based 33 as well as in situ vibrational spectroscopies 31 , 34 – 36 , and in situ electrochemical transmission electron microscopy (TEM) 37 – 39 were used to record changes in catalyst chemical state 40 , 41 , local structure 13 , or intermediates 42 . However, to date, real-time tracking individual CO2RR product yields and product onset potentials on OD-Cu catalysts at fast time scales under non-stationary, transient conditions has remained very challenging.…”

Highly Efficient Electroreduction of CO2 to C2+ Alcohols on Heterogeneous Dual Active Sites

“…The Cu-based catalysts are the most promising electrocatalysts for converting CO 2 into C2 + products. [16][17][18][19] However, the most Cu-based catalysts generally favor the production of ethylene during CO 2 RR. [20][21][22][23] To improve the selectivity of C2 + alcohols, different methods have been applied to modify the Cu-based catalysts, including modifying morphology, [24] using two metals, [25] doping with a heteroatom, [26] and modifying with other molecules.…”

Comparing Molecular Mechanisms in Solar NH3 Production and Relations with CO2 Reduction

“…In multi-carbon CO 2 RR, a large range of mechanistic hypotheses have also been indicated sometimes based on theoretical modeling [ 37 , 72 , 73 , 74 , 92 , 93 , 94 , 95 , 96 , 97 , 98 , 99 , 100 , 101 ]. The proposals are different in terms of the mechanism, type of intermediates and active sites.…”

“…Other authors instead indicate the need to have specific surface sites on the electrocatalyst. Li et al [ 94 ] indicated that CO 2 to C2+ conversion requires an enriched disorder in the copper compared to crystalline Cu, obtained by electrochemical nanocrystal scrambling, i.e., the dynamic fusion of Cu nanoparticles under CO 2 reducing conditions to form multi-carbon active scrambled nanocrystals. It is not well described which new type of active sites forms in this scrambling mechanism, or the influence on the mechanism, but it is hypothesized that this leads to a higher population of strongly bound *CO (the asterisk indicates a surface-bound species), due to disorder-induced microstrain that alleviates the undesired repulsive interactions of a high density of bound *CO [ 102 ], comparable to the creation of optimal geometries in enzymatic systems.…”