 This study proposes a novel electrochemical system that uses proton, bicarbonate, CO2 mass transport management and in-situ copper, CU activation to convert CO2 into methane, CH4. This system achieves high CH4 selectivity at high currents, which is essential for the long-term and large-scale storage of renewable electricity. This article was authored by Cornelius AO DeSangio, Guarui GAO, Jackson Crane, and others.