CO2 electrochemical reduction to hydrocarbons and hydrogen evolution reaction with bimetallic NiCu/C catalysts

The electrochemical reduction reaction of CO 2 (CO 2 RR) was comparatively investigated using a series of NiCu/C electrocatalysts in KHCO 3 and KOH electrolytes in the presence and absence of CO 2 . The catalysts consisted of Cu 0 , Cu 2 O, CuO, Cu(OH) 2 , NiO, NiOOH, and Ni(OH) 2 phases. The CO 2 RR measurements demonstrated that KHCO 3 acts as an intrinsic CO 2 source rather than a sole supporting electrolyte. The formation of hydrocarbons species (CH 4 + , CH 2 + , C 2 H 4 + and C 2 H 5 + ) and HCHO originate predominantly from bicarbonate electrolyte, indicating that changes in CO 2 /HCO 3 - equilibrium induced by the applied potential could lead to in situ generation and subsequent reduction of CO 2 at the electrode surface and interfaces. Results obtained from in situ differential electrochemical mass spectrometry (in situ DEMS) analysis confirmed a competition between CO 2 RR and hydrogen evolution reaction (HER) occurring. The Ni 50 Cu 50 /C catalyst exhibited a superior CO 2 RR performance, characterized by significant enhancement of CO 2 RR activity and effective suppression of HER. In lower concentration of KHCO 3 , CO 2 supplied from an external feed, actively participates in CO 2 RR. However, in higher concentration of KHCO 3 , CO 2 RR was not clearly affected by CO 2 bubbling. By varying the concentration of KHCO 3 , bicarbonate-driven effects from CO 2 dissolution on both CO 2 RR and HER could be well controlled.