Harnessing Protonated 2,2′-Bipyridinium Salts as Powerful Brønsted Acid Catalysts in Organic Reactions

It is the first time that the readily available protonated 2,2′-bipyridinium salts are used as Brønsted acid catalysts to accelerate a series of organic transformations that included the hydration of aromatic alkynes, etherification of alcohols, cyclotrimerization of aliphatic aldehydes, Ritter reaction, Mannich reaction, Biginelli reaction, preparation of substituted alkenes from alcohols, synthesis of spirooxindole, bisindolylmethane, and noncyclized tetraketone with good to excellent yields. These results strongly suggest that there exists enormous potentiality in the development of the protonated 2,2′-bipyridinium catalytic system

Electroreduction of Nitrite to Ammonia over a Cobalt Single-Atom Catalyst

Electrochemical nitrite-to-ammonia reduction (NO2RR) holds great promise for converting harmful NO2– into valuable NH3. Herein, we develop Co single atoms dispersed on a C3N4 substrate (Co1/C3N4) as an efficient catalyst toward the NO2RR. Experimental and theoretical investigations reveal that single-atom Co sites can effectively active NO2– and optimize the formation energy of the key *NOH intermediate to promote the NO2– → NH3 energetics. Remarkably, Co1/C3N4 equipped in a flow cell delivers the exceptional NH3–Faradaic efficiency of 97.9% and NH3 yield rate of 1080.3 μmol h–1cm–2 at an industrial-level current density of 355 mA cm–2, along with a long-term durability of 100 h of electrolysis, showing the considerable potential for practical NH3 electrosynthesis

Pd₁Cu Single-Atom Alloys for High-Current-Density and Durable NO-to-NH₃ Electroreduction

Electrochemical reduction of NO to NH3 (NORR) offers a prospective method for efficient NH3 electrosynthesis. Herein, we first design single-atom Pd-alloyed Cu (Pd1Cu) as an efficient and robust NORR catalyst at industrial-level current densities (>0.2 A cm–2). Operando spectroscopic characterizations and theoretical computations unveil that Pd1 strongly electronically couples its adjacent two Cu atoms (Pd1Cu2) to enhance the NO activation while promoting the NO-to-NH3 protonation energetics and suppressing the competitive hydrogen evolution. Consequently, the flow cell assembled with Pd1Cu exhibits an unprecedented NH3 yield rate of 1341.3 μmol h–1 cm–2 and NH3–Faradaic efficiency of 85.5% at an industrial-level current density of 210.3 mA cm–2, together with an excellent long-term durability for 200 h of electrolysis, representing one of the highest NORR performances on record

p‑Block Antimony Single-Atom Catalysts for Nitric Oxide Electroreduction to Ammonia

Electrocatalytic NO reduction to NH3 (NORR) offers a prospective approach to attain both harmful NO removal and efficient NH3 electrosynthesis. Main-group p-block metals are promising NORR candidates but still lack adequate exploration. Herein, p-block Sb single atoms confined in amorphous MoO3 (Sb1/a-MoO3) are designed as an efficient NORR catalyst, exhibiting the highest NH3 yield rate of 273.5 μmol h–1 cm–2 and a NO-to-NH3 Faradaic efficiency of 91.7% at −0.6 V vs RHE. In situ spectroscopic characterizations and theoretical computations reason that the outstanding NORR performance of Sb1/a-MoO3 arises from the isolated Sb1 sites, which can optimize the adsorption of *NO/*NHO to lower the reaction energy barriers and simultaneously exhibit a higher affinity to NO than to H2O/H species. Moreover, our strategy can be extended to prepare Bi1/a-MoO3, showing a high NORR property, demonstrating the immense potential of p-block metal single-atom catalysts toward the high-performing NORR electrocatalysis