Building of rich (111) grain boundary in copper for syngas in electrochemical CO2 reduction

Building of grain boundary (GB) in Cu-based catalysts has been demonstrated to be an efficient strategy to control the product selectivity of electrochemical CO2 reduction reaction (eCO2RR). However, the fabrication and modulation of GBs in Cu are still challenging. In this study, a series of bare Cu catalysts with controllable density of Cu(111) GBs were investigated systematically for eCO2RR. These catalysts exhibit superior eCO2RR performance for syngas production with a high FE of ∼80 % and tunable H2/CO ratio of 0.46–2.78. Three-dimensional wormlike Cu with abundant (111) GBs displays a stable H2/CO ratio of ∼0.5 over a wide potential range from −0.9 to −1.2 V (vs. RHE). In situ Raman and ATR-SEIRAS spectroscopy combined with DFT calculations reveal that Cu(111) GBs enhance the adsorption of CO2, lower the energy barriers of CO2 to *COOH and *CO, further highlighting the potential to control syngas production with desirable proportion over Cu-based catalysts. [Display omitted] •Controllable density of (111) grain boundaries (GBs) were fabricated on bare Cu catalysts.•Cu(111) GBs facilitate the activity of eCO2RR-to-CO and inhibit the hydrogen evolution reaction.•The selectivity for syngas is as high as ∼80 % with desirable H2/CO ratio of 0.46−2.78.•Cu(111) GBs facilitate CO2 adsorption and lower the energy barriers of CO2 to *COOH and *COOH to CO.