Boosting Nitrogen Activation via Ag Nanoneedle Arrays for Efficient Ammonia Synthesis

Electrocatalytic N₂ reduction reaction (eNRR) provides a promising carbon-neutral and sustainable ammonia-synthesizing alternative to the Haber-Bosch process. However, the nonpolar N₂ has significant thermodynamic stability and requires ultrahigh energy to break down the N≡N bond. Here, we report the construction of local enhanced electric fields (LEEFs) by Ag nanoneedle arrays to promote N≡N fracture thus assisting the eNRR. The LEEFs could induce charge polarization on nitrogen atoms and reduce the energy barrier in the N₂ first-protonation step. The detected N─N and N─H intermediates prove the cleavage of the N≡N bond and the hydrogenation of N₂ by LEEFs. The increased LEEFs lead to logarithmic growth rates for the targeted eNRR and exponential growth rates for the unavoidable competitive hydrogen evolution reaction. Thus, regulation and tuning of LEEFs to ∼4 × 10⁴ kV m^-1 endows the raise of eNRR to the summit, achieving high ammonia selectivity with a Faradaic efficiency of 72.3 ± 4.0%.

Observation of the onset of a blue jet into the stratosphere

Blue jets are lightning-like, atmospheric electric discharges of several hundred millisecond duration that fan into cones as they propagate from the top of thunderclouds into the stratosphere¹. They are thought to initiate in an electric breakdown between the positively charged upper region of a cloud and a layer of negative charge at the cloud boundary and in the air above. The breakdown forms a leader that transitions into streamers² when propagating upwards³. However, the properties of the leader, and the altitude to which it extends above the clouds, are not well characterized⁴. Blue millisecond flashes in cloud tops^5,6 have previously been associated with narrow bipolar events^7,8, which are 10- to 30-microsecond pulses in wideband electric field records, accompanied by bursts of intense radiation at 3 to 300 megahertz from discharges with short (inferred) channel lengths (less than one kilometre)^9-11. Here we report spectral measurements from the International Space Station, which offers an unimpeded view of thunderclouds, with 10-microsecond temporal resolution. We observe five intense, approximately 10-microsecond blue flashes from a thunderstorm cell. One flash initiates a pulsating blue jet to the stratopause (the interface between the stratosphere and the ionosphere). The observed flashes were accompanied by 'elves'¹² in the ionosphere. Emissions from lightning leaders in the red spectral band are faint and localized, suggesting that the flashes and the jet are streamer ionization waves, and that the leader elements at their origin are short and localized. We propose that the microsecond flashes are the optical equivalent of negative narrow bipolar events observed in radio waves. These are known to initiate lightning within the cloud and to the ground, and blue lightning into the stratosphere, as reported here.