Ammonia plays a signi cant role in agriculture and the next-generation carbon-free energy supply.Electrocatalytic nitrate reduction to NH 3 is attractive for nitrate removal and NH 3 production under ambient conditions. However, the energy e ciency is limited by the high reaction overpotential. Here, we propose a three-step relay mechanism composed of a spontaneous redox reaction, electrochemical reduction, and electrocatalytic reduction to overcome this issue. Ru x Co y alloys are designed and adopted as model catalysts. Ru 15 Co 85 exhibits an onset potential of +0.4 V versus a reversible hydrogen electrode and an energy e ciency of 41.54 ± 1.72 %, which are both the best records. The high performance results in a low production cost of $0.49 ± 0.02 /kg ammonia ($0.58~1.02/kg ammonia sold in the USA).Electrochemical in situ spectroscopy and theoretical simulations indicate that the three-step relay mechanism leads to excellent catalytic performance on Ru 15 Co 85 and can be extended to Ru x Fe y and Ru x Ni y alloys.

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Developing efficient catalytic materials and unveiling the active species are significant for selective hydrogenation of CO2 to C2+ hydrocarbons. Fe2N@C nanoparticles were reported to exhibit outstanding performance toward selective CO2 hydrogenation to C2+ hydrocarbons (C2+ selectivity: 53.96 %; C2‐C4= selectivity, 31.03 %), outperforming corresponding Fe@C. In situ X‐ray diffraction, ex situ Mössbauer and X‐ray photoelectron spectra revealed that iron nitrides were in situ converted to highly active iron carbides, which acted as the real active species. Moreover, the combined results of in situ diffuse reflectance infrared Fourier transform spectroscopy and control experiments suggested an in situ formed carbonyl iron‐mediated conversion mechanism from iron nitrides to iron carbides.

Highly chemo-and regioselective semihydrogenation of alkynes is significant and challenging for the synthesis of functionalized alkenes. Here, a sequential self-template method is used to synthesize amorphous palladium sulfide nanocapsules (PdS x ANCs), which enables electrocatalytic semihydrogenation of terminal alkynes in H 2 O with excellent tolerance to easily reducible groups (e.g., C−I/Br/Cl, C�O) and the metal center deactivating skeletons (e.g., quinolyl, carboxyl, and nitrile). Mechanistic studies demonstrate that specific σ-alkynyl adsorption via terminal carbon and negligible alkene adsorption on isolated Pd 2+ sites ensure successful synthesis of various alkenes with outstanding time-irrelevant selectivity in a wide potential range. The key hydrogen and carbon radical intermediates are validated by electron paramagnetic resonance and high-resolution mass spectrometry. Gram-scale synthesis of 4-bromostyrene and expedient preparation of deuterated alkene precursors and drugs with D 2 O show promising applications. Impressively, PdS x ANCs can be applied to the prevailing thermocatalytic semihydrogenation of functionalized alkyne using H 2 .