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

Abstract 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, RuO₂). 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||RuO₂. 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.