Unravelling the performance of N-doped lignin-derived carbon materials during electro-catalytic reduction of CO2

Electrocatalyst, as a key factor for electrocatalytic CO2 reduction reaction (CO2RR) has been extensively researched for its high activity and selectivity, cost-effectiveness, and straightforward preparation methods. A series of N-doped porous carbons, used as CO2RR electrocatalysts, were prepared from solid waste lignin with the assistance of ZnCl2 as activator and melamine as nitrogen source. The addition of N atoms to lignin-derived carbon materials can significantly improve the performance of CO2RR compared with undoped lignin-derived carbon materials. The texture of the N-doped lignin-derived carbon materials, including specific surface area, pore structure, and the type of active sites, can be finely tuned by adjusting the carbonization temperature from 700 °C to 1000 °C. N-doped lignin-derived carbon materials obtained under 800 °C exhibitd the highest CO selectivity because of its high ratio of mesoporosity and suitable active sites promoting the conversion of CO2 to CO. The N-doped lignin-derived carbon materials obtained under 900 °C had the largest range of adjustable syngas H2/CO ratios from 2.3 to 8.0 due to its sensitivity to the applied voltages. The CO2RR performance of N-doped lignin-derived carbon materials were influenced by multiple physicochemical properties, including the configuration of the N-dopant, porosity and degree of graphitization. This work not only offers a fresh perspective on the utilization of lignin-derived carbon materials, but also presents an efficient method for creating carbon-based electrocatalysts for CO2RR by using naturally abundant precursors.