Electrocatalytic CO 2 reduction reaction is regarded as an intriguing route for producing renewable chemicals and fuels, but its development is limited by the lack of highly efficient and stable electrocatalysts. Herein, we propose the pipet-like bismuth (Bi) nanorods semifilled in nitrogen-doped carbon nanotubes (Bi-NRs@NCNTs) for highly selective electrocatalytic CO 2 reduction. Benefited from the prominent capillary and confinement effects, the Bi-NRs@NCNTs act as nanoscale conveyors that can significantly facilitate the mass transport, adsorption,and concentration of reactants onto the active sites, realizing rapid reaction kinetics and low cathodic polarization. The spatial encapsulation and separation by the NCNT shells prevents the self-aggregation and surface oxidation of Bi-NRs, increasing the dispersity and stability of the electrocatalyst. As a result, the Bi-NRs@NCNTs exhibit high activity and durable catalytic stability for CO 2 -to-formate conversion over a wide potential range. The Faradaic efficiency for formate production reaches 90.9% at a moderate applied potential of −0.9 V vs reversible hydrogen electrode (RHE).

The electrochemical coreduction of carbon dioxide (CO 2 ) and nitrogenous species (such as NO 3 − , NO 2 − , N 2 , and NO) for urea synthesis under ambient conditions provides a promising solution to realize carbon/nitrogen neutrality and mitigate environmental pollution. Although an increasing number of studies have made some breakthroughs in electrochemical urea synthesis, the unsatisfactory Faradaic efficiency, low urea yield rate, and ambiguous C−N coupling reaction mechanisms remain the major obstacles to its large-scale applications. In this review, we present the recent progress on electrochemical urea synthesis based on CO 2 and nitrogenous species in aqueous solutions under ambient conditions, providing useful guidance and discussion on the rational design of metal nanocatalyst, the understanding of the C−N coupling reaction mechanism, and existing challenges and prospects for electrochemical urea synthesis. We hope that this review can stimulate more insights and inspiration toward the development of electrocatalytic urea synthesis technology.

Electrochemically converting nitrate to ammonia is a promising route to realize artificial nitrogen recycling. However, developing highly efficient electrocatalysts is an ongoing challenge. Herein, we report the construction of stable and redox-active zirconium metal−organic frameworks (Zr-MOFs) based on Zr 6 nanoclusters and redox-reversible tetrathiafulvalene (TTF) derivatives as inorganic nodes and organic linkers, respectively. The redox-active Zr-MOF can facilitate the in situ reduction of noble metal precursors free of external reductants and realize the uniform nucleation of noble metal nanodots (NDs) on Zr-MOF, achieving the preparation of M-NDs/Zr-MOF (M = Pd, Ag, or Au). The highly porous Zr-MOF with good conductivity can facilitate the mass transfer process. Among the M-NDs/Zr-MOF catalysts, Pd-NDs/Zr-MOF exhibits the highest electrocatalytic activity, delivering a NH 3 yield of 287.31 mmol•h −1 •g −1 cat . and a Faradaic efficiency of 58.1%. The proposed interfacial reduction nucleation strategy for anchoring M NDs on Zr-MOFs can be applied to other challenging energy conversion reactions.