Imidazole-Modified Lignin as a Suitable Substrate for Synthesis of N and S Co-Doped Carbon Supported Cobalt Sulfide Dual-Functional Electrocatalyst for Overall Water Splitting

The hydrogen production by water electrolysis has attracted great research interest as a sustainable approach for clean energy production. However, such process is plagued by the use of high-cost precious metal-based catalysts (such as Pt, RuO 2 ). Hereby, the use of a low-cost Nitrogen and Sulfur co-doped carbon-supported cobalt sulfide dual-functional electrocatalyst derived from imidazole modified lignin for overall water splitting is presented. To introduce nitrogen and sulfur heteroatoms in the carbon structure, lignin is modified by imidazolation through thiol-alkynes click reaction. Imidazole-lignin shows a strong chelation tendancy with cobalt salt, and N and the S co-doped cobalt sulfide catalyst (IL-Co@GC-PO) is obtained by pyrolysis. The IL-Co@GC-PO has an oxygen evolution potential of 1.57 V and a hydrogen evolution overpotential of 204 mV at a current density of 10 mA cm −2 . During the overall water splitting process, the IL-Co@GC-PO catalysts require only 1.58 V to reach a current density of 10 mA cm −2 , which is equivalent to the performance of the system composed of the noble metal Pt/C||RuO 2 . This work not only provides a strategy for the preparation of N and S co-doped cobalt sulfide catalysts, but also provides guidance for using lignin as a carbon source to design and develop cheap electrocatalysts.