The increase in the concentration of CO2 in the atmosphere has become a global, political, economic, social and environmental issue. Among other alternatives, the electrochemical CO2 Reduction Reaction (CO2RR), in particular, has demonstrated a great potential to mitigate this process, as it is capable of converting the CO2 molecule to others of greater value-added.Copper is the only metal reported in the literature capable of coupling two carbons (C-C) in CO2 electroreduction, generating molecules that have a higher energy value, such as C2H4 and C2H5OH. However, several other compounds are also generated, such as CO, CH4, HCOO -, in addition to H2 from H2O parallel electrolysis, resulting in poor selectivity. Recent work has attempted to optimize CO2RR through surface functionalization, for example, with the use of organic molecules or molecular complexes. Phenanthroline derivatives have already been reported with excellent results for products with two carbons (C2), while the adsorption of [Cu(phen)2] 2+/+ complexes on graphene surface demonstrated high CO production. However, no study has yet been carried out on the in situ formation of copper-phenanthroline complexes (Cu-phen) for CO2RR with copper electrocatalysts. Is this work, the electrocatalytic activity of the copper/phenanthroline/KHCO3 system was evaluated compared to the conversion of the CO2 molecule in C2 products, using differential electrochemical mass spectrometry (DEMS) and chromatography techniques for monitoring and quantifying the distribution of reaction products. An evident selectivity for C2H4 was observed, with an increase of almost six times compared to copper without the addiction of phenanthroline, in addition to a decrease in H2 and C1 products, suppressing CH4 and CO (<3%). It was found that Cu-phen complexes are formed during the open circuit potential (OCP), due to the copper surface oxidation and the consequent interaction with amine nitrogen. Furthermore, surface characterizations indicated the presence of the complexes Cu-fen at the end of the electrolysis. From the analysis of the results, it is suggested that a possible mechanism involves a Tandem effect, from the CO2-to-CO conversion by the adsorbed Cu-phen complex, followed by electroreduction of CO-to-C2H4 in neighboring sites of metallic copper. Additionally, it was evaluated that deposition of Cu-phen complexes can also accumulate OHas a counterion, foment even more C2 products.