This leads to a significant reduction in ethylene production, as it falls outside the low voltage region for ethylene formation on Cu(100) . Therefore, even though ethylene is still produced, it is produced at a lower current density as shown in Fig. . Remarkably, pH recorded in this voltage region (-1.05 to -1.15 V) aligns with the optimal local pH for methane production, ranging from 10 to 11.5. Beyond this optimal pH range for methane production, as pH continues to increase, there is a decline in the current density and Faradaic efficiency of methane, paving the way for hydrogen production. This shift is notable since Cu(100) exhibits an enhanced ability to catalyse the hydrogen evolution reaction (HER). Secondly, the shorter residence time for electrochemical reduction due to the low surface area of the catalysts used in this work, promotes higher methane selectivity which is closely linked to local pH of the reaction medium. This is also coupled with the impact of low tortuosity on low catalytic surface area as described in our previous study.