Electron and Proton Separation on Ru-Based Catalysts Promotes Ammonia Synthesis
Ammonia synthesis remains dominated by the Haber-Bosch process, which operates at 400–500 °C and 150–300 bar, consumes 1–2% of global energy, and emits ~1.4% of global CO2. Ru-based catalysts supported on carbon and promoted with basic oxides (Ba, Cs, La) exhibit high activity under mild conditions, but conventional designs suffer from a trade-off: BaO domains block Ru active sites while attempting to donate electrons. Lee et al. (Nat Catal, 2025, 8: 248–256) resolved this by using conductive carbon to bridge isolated Ru and BaO domains, enabling long-range H+/e− pair migration. Screening eleven carbon supports, they identified N-doped multi-walled carbon nanotubes (10–20 nm diameter, N-MWNT-1) with the lowest work function as optimal. At a Ba/Ru molar ratio of 0.75, the catalyst achieved an NH3 production rate 7.4 times higher than conventional BaO-promoted Ru catalysts under 573 K and 1.0 MPa, using high-purity H2 and N2 (99.999%, O2 <0.4 ppm, H2O <0.7 ppm). This design decouples proton and electron storage, preventing BaO-induced blockage of Ru surfaces and enabling superior activity and stability. The Ba-Ru/carbon catalyst offers a transformative pathway for reducing energy consumption and integrating with electrolytic hydrogen production in industrial ammonia synthesis.