Carbon Fiber Supported Binary Metal Sulfide Catalysts with Multi-Dimensional Structures for Electrocatalytic Nitrogen Reduction Reactions Over a Wide pH Range

Green and environmentally friendly electrocatalytic nitrogen (N-2) fixation to synthesize ammonia (NH3) is recognized as an effective method to replace the traditional Haber-Bosch process. However, the difficulties in N-2 adsorption and fracture of hard N equivalent to N bond still remain major challenges in electrocatalytic N-2 reduction reactions (NRR). From the perspectives of enhancing N-2 adsorption and providing more catalytic sites, two-dimensional (2D) FeS2 nanosheets and three-dimensional (3D) metal organic framework-derived ZnS embedded within N-doped carbon polyhedras are grown on the carbon cloth (CC) template in this work. Thus, a composite NRR catalyst with multi-dimensional structures, which is signed as FeS2/ZnS-NC@CC, is obtained for using over a wide pH range. The uniform distribution of hollow ZnS-NC frameworks and FeS2 nanosheets on the surface of CC largely increase the N-2 enrichment efficiency and offer more active sites, while the CC skeleton acts as an independent conductive substrate and S-doping helps promote the fracture of N equivalent to N bond during the NRR reaction. As a result, the FeS2/ZnS-NC@CC electrode achieves a high Faraday efficiency of 46.84% and NH3 yield of 58.52 mu g h(-1) mg(-1) at -0.5 V vs. Ag/AgCl in 0.1 M KOH. Furthermore, the FeS2/ZnS-NC@CC electrode displays excellent NRR catalytic activity in acidic and neutral electrolytes as well, which outperforms most previously reported electrocatalysts including noble metals. Therefore, this work provides a new way for the design of multi-dimensional electrocatalysts with excellent electrocatalytic efficiency and stability for NRR applications.

Automated summary

This study improves the efficiency of N-2 adsorption and provides more active sites by designing a multi-dimensional electrocatalyst on a new composite material, achieving excellent catalytic activity in NRR over a wide pH range. The FeS2/ZnS-NC@CC electrode shows high Faraday efficiency and NH3 yield, outperforming most previously reported electrocatalysts, including noble metals, in acidic and neutral electrolytes.