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Electrochemical reduction reaction of CO₂(CO₂RR) is a promising technology for alleviating the global warming caused by the emission of CO₂. This technology, however, is still in the stage of finding efficient catalysts. The catalysts must be able to convert CO₂to other carbon‐based products with high activity and selectivity to valuable chemicals. In this review, previous development of heteroatom‐doped metal‐free carbon materials (H‐CMs) is briefly summarized. Recent progress of CO₂RR promoted by metal single‐atom catalysts (M‐SACs) is then discussed with emphasis on the synthesis of M‐SACs, the catalytic performance, and reaction mechanisms. The high temperature pyrolysis method and electrodeposition are attracting attentions recently to prepare M‐SACs with high metal loading on N‐doped carbon materials, a very active M‐SACs system for the CO₂RR. Theoretical calculations of free energy change on active sites, the Operando X‐ray absorption near edge structure (XANES), and Bader charge analysis reveal a significant role of metal oxidation state and charge transfer between metal atoms and absorbed CO. The challenges and perspectives for the extensive applications of M‐SACs in CO₂RR are also discussed in this review.

 

Polymeric nitrogen (PN) belongs to a general family of materials containing all-nitrogen molecules or clusters. Although it is rare and challenging to synthesize PN members, they are attracting increasing scientific attention due to their high energy storage capacity and possible use as a green catalyst. A few theoretical calculations predicted the possible PN phases from N 2 gas, but they all require extremely high pressures and temperatures to synthesize. In this work, a practical way to synthesize N 8 polymeric nitrogen from an N 3 − precursor is elucidated using density functional theory calculations. The detailed mechanism, , is determined. The calculated energy barriers indicate that the first step is the rate-limiting step. This result guides us to rationally synthesize N 8 under UV (254 nm) irradiation, chosen based on the calculated absorption spectrum for the azide anion. As expected, UV irradiation enhances N 8 yields by nearly four times. This provides an interesting route to the scalable synthesis of high energy density N 8 compounds.