Enhanced CO2 Electroreduction Selectivity to n -Propanol over CdS-Modified Cu2O

Abstract Copper (Cu) has captured a lot of attention as a superior metal catalyst for CO2RR (CO2 reduction reaction), inducing C2+ product formation. Achieving highly tailored product selectivity and a restricted product dispersion across Cu-based electrocatalysts remains a significant issue to this day. The facile synthesis of different loadings of CdS onto Cu2O (CuCdX) was conducted under moderate heating conditions under a controlled agitation process. The electrochemical performance of all Cu2O/CdS compositions shows improved results compared to that of pristine Cu2O and CdS materials. The maximum current density of −141.34 mA/cm2 of 9.84% CdS loading onto Cu2O (CuCd4) was experienced in a CO2-saturated aqueous KHCO3 electrolyte medium at a potential range of +1.2 to −1.331 V vs RHE. The highest electrochemical active surface area (ECSA) (0.6156 cm2) and smaller Tafel slope value for the formation of n-propanol (294.7 mV/dec) over the CuCd4 catalyst exhibit excellent activity toward CO2 reduction at a pH of 8.0 in an aqueous medium in the H-cell reactor. The selective production of n-propanol with a FE of 32.77% and an ECSA-normalized partial current density of −3.88 mA/cm2 was achieved for the 9.84% CdS-loaded Cu2O composite at −1.131 V vs RHE. The formation of ethanol and acetate, with their respective highest Faradaic efficiency of 9.45% and 15.19%, occurred at the potential of −0.831 V and −0.931 V vs RHE, respectively. The density functional theory (DFT) approach was implemented to produce the density of states (DOS) of the Cu2O lattice and calculate the free energies of the several intermediates produced during the CO2 electroreduction to n-propanol on the (111) surface of CuCd4. The chronoamperometry study of the electrocatalyst in a CO2-presaturated KHCO3 medium for 12 h and post-electrolysis material characterization feature the outstanding stability and excellent structural integrity of the material for the reaction.