In this section, we explore how the applied voltage, CO2 concentration and H + concentration (local pH) influence product selectivity on Cu(100) surface. In CO2RR, the reaction mechanism is governed by a series of electron and proton transfers leading to specific products. Therefore, tuning the reaction landscape towards desired products involves manipulating the electrode potential (electrons) and solution pH (H + ). The results discussed in this section pertain strictly to those observed on Cu(100).