Electrochemical urea synthesis by co-reduction of CO_(2) and nitrate with Fe^(Ⅱ)-Fe^(Ⅲ)OOH@BiVO_(4) heterostructures

Traditional urea synthesis under harsh conditions is usually associated with high energy input and has aroused severe environmental concerns.Electrocatalytic C-N coupling by converting nitrate and CO_(2) into urea under ambient conditions represents a promising alternative process.But it was still limited by the strong competition between nitrate electrochemical reduction(NO_(3)ER) and CO_(2) electrochemical reduction(CO_(2)ER).Here,Fe^(Ⅱ)-Fe~ⅢOOH@BiVO_(4)-n heterostructures are constructed through hydrothermal synthesis and exhibited superior performance toward urea electrosynthesis with NO_(3)~-and CO_(2) as feedstocks.The optimized urea yield and Faradaic efficiency over Fe^(Ⅱ)-Fe~ⅢOOH@BiVO_(4)-2 can reach13.8 mmol h^(-1) g^(-1) and 11.5% at-0.8 V vs.reversible hydrogen electrode,which is much higher than that of bare FeOOH(3.2 mmol h^(-1) g^(-1) and 1.3%),pristine BiVO_(4)(2.0 mmol h^(-1) g^(-1) and 5.4%),and the other Fe^(Ⅱ)-Fe~ⅢOOH@BiVO_(4)-n(n=1,3,5) heterostructures.Systematic experiments have verified that BiVO_(4)and FeOOH are subreaction active sites towards simultaneous CO_(2)ER and NO_(3)ER,respectively,achieving co-activation of CO_(2) and NO_(3)~-on Fe^(Ⅱ)-Fe~ⅢOOH@BiVO_(4)-2.Moreover,the urea synthesis via the ^(*)CO and NO*intermediates and C-N coupling was confirmed by the in situ Fourier transform infrared spectroscopy.This work not only alleviates the CO_(2) emission and nitrate pollution but also presents an efficient catalyst for synergistic catalysis towards sustainable urea synthesis.

W/Mo-polyoxometalate-derived electrocatalyst for high-efficiency nitrogen fixation

Ammonia is the feedstock chemical for most fertilizers and the alternative of renewable energy carriers.Environmentally benign electrochemical nitrogen reduction reaction (NRR) under mild conditions has been recognized as one of the most attractive strategies for N_(2) fixation.Herein,inspired by Mobased nitrogenase,W/Mo-doping electrocatalysts were developed with mixed-metal polyoxometalate H_(3)PW_6Mo_6O_(40) as the precursor for high performance electrocatalytic NRR.Trace amount of Pt was transplanted on the surface of W/Mo@rGO via in situ electroplating treatment to further improve the NRR performance.The resulting Pt-W/Mo@rGO-6 achieves excellent performance for NRR with a high NH_(3)yield of 79.2μg h^(-1)mg_(cat)^(-1) due to the multicomponent synergistic effect in the composite catalyst.The Pt-W/Mo@rGO-6 represents the first example of highly efficient NRR electraocatalyst derived from mixed-metal polyoxometalate,which exhibits outstanding stability confirmed by the constant catalytic performance over 24 h chronoamperometric test.This finding opens a new avenue to construct highly efficient NRR electrocatalyst by employing mixed metal polyoxometalate as the precursor under ambient conditions.

Porousβ-FeOOH nanotube stabilizing Au single atom for highefficiency nitrogen fixation

Electrochemical nitrogen reduction reaction(NRR)under ambient conditions is highly desirable to achieve sustainable ammonia(NH3)production via an alternative carbon free strategy.Single-atom catalysts(SACs)with super high atomic utilization and catalytic efficiency exhibit great potential for NRR.Herein,a high-performance NRR SAC is facilely prepared via a simple deposition method to anchor Au single atoms onto porousβ-FeOOH nanotubes.The resulting Au-SA/FeOOH can efficiently drive NRR under ambient conditions,and the NH3 yield reaches as high as 2,860μg·h^(-1)·mg_(Au)^(-1)at-0.4 V vs.reversible hydrogen electrode(RHE)with 14.2%faradaic efficiency,much superior to those of all the reported Au-based electrocatalysts.Systematic investigations demonstrate that the synergy of much enhanced N_(2)adsorption,directional electron export,and mass transfer ability in Au-SA/FeOOH greatly contributes to the superior NRR activity.This work highlights a new insight into the design of high efficient NRR electrocatalysts by combination of porous metal oxide matrix and highly active single-atom sites.