A Universal Approach for Sustainable Urea Synthesis via Intermediate Assembly at the Electrode/Electrolyte Interface.

Electrocatalytic C-N coupling process is indeed a sustainable alternative for direct urea synthesis and co-upgrading of carbon dioxide and nitrate wastes. However, the main challenge lies in the unactivated C-N coupling process. Here, we proposed a strategy of intermediate assembly with alkali metal cations to activate C-N coupling at the electrode/electrolyte interface. Urea synthesis activity follows the trend of Li+

Oxygen-Bridged Copper-Iron Atomic Pair as Dual-Metal Active Sites for Boosting Electrocatalytic NO Reduction.

Electrocatalytic reduction of nitric oxide (NO) to ammonia (NH3 ) is a promising approach to NH3 synthesis. However, due to the lack of efficient electrocatalysts, the performance of electrocatalytic NO reduction reaction (NORR) is far from satisfactory. Herein, it is reported that an atomic copper-iron dual-site electrocatalyst bridged by an axial oxygen atom (OFeN6 Cu) is anchored on nitrogen-doped carbon (CuFe DS/NC) for NORR. The CuFe DS/NC can significantly enhance the electrocatalytic NH3 synthesis performance (Faraday efficiency, 90%; yield rate, 112.52 µmol cm-2  h-1 ) at -0.6 V versus RHE, which is dramatically higher than the corresponding Cu single-atom, Fe single-atom and all NORR single-atom catalysts in the literature so far. Moreover, an assembled proof-of-concept Zn-NO battery using CuFe DS/NC as the cathode outputs a power density of 2.30 mW cm-2 and an NH3 yield of 45.52 µg h-1  mgcat -1 . The theoretical calculation result indicates that bimetallic sites can promote electrocatalytic NORR by changing the rate-determining step and accelerating the protonation process. This work provides a flexible strategy for efficient sustainable NH3 synthesis.

Electrocatalytic Urea Synthesis with 63.5 % Faradaic Efficiency and 100 % N-Selectivity via One-step C-N coupling.

Electrocatalytic urea synthesis via coupling N2 and CO2 provides an effective route to mitigate energy crisis and close carbon footprint. However, the difficulty on breaking N≡N is the main reason that caused low efficiencies for both electrocatalytic NH3 and urea synthesis, which is the bottleneck restricting their industrial applications. Herein, a new mechanism to overcome the inert of the nitrogen molecule was proposed by elongating N≡N instead of breaking N≡N to realize one-step C-N coupling in the process for urea production. We constructed a Zn-Mn diatomic catalyst with axial chloride coordination, Zn-Mn sites display high tolerance to CO poisoning and the Faradaic efficiency can even be increased to 63.5 %, which is the highest value that has ever been reported. More importantly, negligible N≡N bond breakage effectively avoids the generation of ammonia as intermediates, therefore, the N-selectivity in the co-electrocatalytic system reaches100 % for urea synthesis. The previous cognition that electrocatalysts for urea synthesis must possess ammonia synthesis activity has been broken. Isotope-labelled measurements and Operando synchrotron-radiation Fourier transform infrared spectroscopy validate that activation of N-N triple bond and nitrogen fixation activity arise from the one-step C-N coupling process of CO species with adsorbed N2 molecules.

C-Bound or O-Bound Surface: Which One Boosts Electrocatalytic Urea Synthesis?

The electrocatalytic C-N coupling from carbon dioxide and nitrate under ambient conditions is kind of sustainable and promising alternative method for urea synthesis. To date, the influence of catalyst surface properties on molecular adsorption configuration and electrocatalytic urea synthesis activity is unclear. In this work, we proposed that the urea synthesis activity is closely linked with the localized surface charge on bimetallic electrocatalysts, it is found that a negatively charged surface induces C-bound path and boosts urea synthesis. The urea yield rate can reach 13.1 mmol g-1 h-1 on negatively charged Cu97 In3 -C, which is about 13 times that of positively charged Cu30 In70 -C counterpart with O-bound surface. This conclusion also applies to Cu-Bi and Cu-Sn systems. The molecular modification shifts the surface of Cu97 In3 -C to positively charged state, which leads to a sharp decline in urea synthesis performance. We demonstrated that the C-bound surface is more favorable than O-bound one to boost electrocatalytic urea synthesis.