||Electrochemical CO2 reduction reaction (CO2RR) is a powerful strategy to control the increasing levels of CO2 emission in atmosphere. Thiolate-protected nickel nanoclusters (NCs) have recently received a significant interest as a promising material for various electrocatalytic applications. Herein, we performed density functional theory calculations to explore CO2 reduction and the competing hydrogen evolution reaction (HER) on Ni4(SCH3)8 (Ni4) and Au-doped Au4Ni2(SCH3)8 (Au4Ni2) NCs. It was determined that fully thiolate protected NCs exhibited low activity towards both reactions. We found that a portion of the thiolate ligands can be removed under the reducing potential and this significantly improved the catalytic activity of both NCs. After partial ligand removal, Ni4 NCs were highly active towards HER, however, they were poisoned by CO* at CO2 reduction conditions. Therefore, we investigated the energetics of CO2RR and HER on CO*-adsorbed NCs. It was found that implanted Au sites of Au4Ni2 NCs do not get poisoned by *CO’s, and they are critical in promoting the CO2RR activity while suppressing the HER activity particularly under CO poisoning conditions.