Carbon dioxide reduction to multicarbon hydrocarbons and oxygenates on plant moss-derived, metal-free, in situ nitrogen-doped biochar

Electrochemical reduction of carbon dioxide (CO2) is considered a promising renewable energy conversion technology, but it remains challenging to find active, stable, low-cost, and highly efficient electrocatalysts for the CO2 conversion. Here, we develop an in situ nitrogen-doped, metal-free, porous biochar from plant moss to catalyze the electrochemical reduction of CO2 into methane (CH4), methanol (CH3OH) and ethanol (C2H5OH) at high current densities and low overpotentials. Using this metal-free biochar electrocatalyst, production rates of approximately 36.1, 32.1, and 18.1 mu g h(-1) cm(-2) towards CH4, C2H5OH, and CH3OH are obtained with Faradaic efficiencies of 56.0%, 26.0% and 10.5%, respectively. In addition, the total faradaic efficiency reaches 92.6% at -1.2 V (vs. Ag/AgCl) with good stability. A favorable pathway for the electrochemical reduction of CO2 over the metal-free biochar is also provided. This study presents a new approach to produce cost-effective, in situ nitrogen-doped porous biochars with excellent efficiency and durability for the electrochemical reduction of CO2. (C) 2020 Elsevier B.V. All rights reserved.