Bimetallic PdFe₃ Nano-Alloy with Tunable Electron Configuration for Boosting Electrochemical Nitrogen Fixation

Electrocatalyst plays animportant role in electrochemical ammonia synthesis by determining the nitrogen reduction reaction pathway. Featuring the inherent half-filled 3d orbitals, ion-based alloy electrocatalysts have been attracting much more attention owing to the controllable driving force to adsorb and activate N equivalent to N bonds. Besides supplying unoccupied d-orbital to accommodate lone-pair electrons to facilitate nitrogen adsorption, donating d-orbital electrons to nitrogen antibonding orbitals to dissociate N equivalent to N bond is demandedas well. By palladium (Pd) to synthesize PdFe3 nano-alloy, numerous Fe 3d orbitals can be reconstructed via charge polarization between Fe and Pd, simultaneously lowering corresponding work functions. Meanwhile, the positively charged Fesites in PdFe3 can strengthen suppress the proton adsorption by electrostatic repulsion. A considerably optimized ammonia production rate of 29.07 mu g h(-1) mg(cat).(-1) and Faradic efficiency of 22.8% are accomplished at a low overpotential of -0.2 V vs. RHE. Density functional theory combined with in-situ ATR-FTIR results confirmthe electrocatalytic nitrogen reduction follows the associative distalmechanism and the electron-deficient Fe induced through Pd facilitates significantly lowering the first-step-protonation energy barrier of only 0.07 eV (*N-2+ *H ->*NNH).