Refining Energy Levels in ReS₂ Nanosheets by Low-Valent Transition-Metal Doping for Dual-Boosted Electrochemical Ammonia/Hydrogen Production

Electrocatalytic nitrogen reduction reaction (NRR) and hydrogen evolution reaction (HER) are intriguing approaches to nitrogen fixation and hydrogen production under ambient conditions, given the need to discover efficient and stable catalysts to light up the “green chemistry” future. However, bottlenecks are often found during N₂/H₂O activation, the very first step of NRR/HER, due to energetic electron injection from the surface of electrocatalysts. It is reported that the bottlenecks for both NRR and HER can be tackled by engineering the energy level via low-valent transition-metal doping, simultaneously, where rhenium disulfide (ReS₂) is employed as a model platform to prove the concept. The doped low-valent transition-metal domains (e.g., Fe, Co, Ni, Cu, Zn) in ReS₂ provide more active sites for N₂/H₂O chemisorption and electron transfer, not only weakening the NN/OH bonds for easier dissociation through proton coupling, but also elevating d-band center toward the Fermi level with more electron energy for N₂/H₂O reduction. As a result, it is found that iron-doped ReS₂ nanosheets wrapped nitrogen-doped carbon nanofiber (Fe-ReS₂@N-CNF) catalyst exhibits superior electrochemical activity with eightfold higher ammonia production yield of 80.4 µg h⁻¹ mg⁻¹ _cat., and lower onset overpotential of 146 mV and Tafel slope of 63 mV dec⁻¹, when comparing with the pristine ReS₂.