Vacancy Engineering of Iron‐Doped W₁₈O₄₉ Nanoreactors for Low‐Barrier Electrochemical Nitrogen Reduction

Abstract

The electrochemical nitrogen reduction reaction (NRR) is a promising energy-efficient and low-emission alternative to the traditional Haber-Bosch process. Usually, the competing hydrogen evolution reaction (HER) and the reaction barrier of ambient electrochemical NRR are significant challenges, making a simultaneous high NH 3 formation rate and high Faradic efficiency (FE) difficult. To give effective NRR electrocatalysis and suppressed HER, the surface atomic structure of W 18 O 49 , which has exposed active W sites and weak binding for H 2 , is doped with Fe. A high NH 3 formation rate of 24.7 mg h À1 mg cat À1 and a high FE of 20.0 % are achieved at an overpotential of only À0.15 V versus the reversible hydrogen electrode. Ab initio calculations reveal an intercalation-type doping of Fe atoms in the tunnels of the W 18 O 49 crystal structure, which increases the oxygen vacancies and exposes more W active sites, optimizes the nitrogen adsorption energy, and facilitates the electrocatalytic NRR.

Confined Fe–Cu Clusters as Sub‐Nanometer Reactors for Efficiently Regulating the Electrochemical Nitrogen Reduction Reaction

“…Thus, the exploration of efficient catalysts for NRR has drawn particular attraction in recent years. [ 5 ] By far, a number of catalysts that are based on metals (e.g., Ru, [ 6 ] Pd, [ 7 ] and Au [ 8 ] ), oxides (e.g., Fe 2 O 3 /carbon nanotube, [ 9 ] W 18 O 49 , [ 10 ] and BiOBr nanosheets [ 11 ] ), sulfides (e.g., FeMoS [ 12 ] ), black phosphorus, [ 13 ] nitrides (e.g., C 3 N 4 [ 14 ] and MoN [ 15 ] ), carbides (MoC [ 16 ] ), MXenes, [ 17 ] and single atoms (e.g., Mo, [ 18 ] B, [ 19 ] W, [ 20 ] and Ru [ 21 ] ) have been investigated.…”

Defective Structures in Metal Compounds for Energy‐Related Electrocatalysis

“…Refilling the anion vacancies with heteroatoms or atomic metal species is not only a feasible and efficient method to improve the stability, but also a potential strategy to further enhance the catalytic performance. [ 16,89–91 ]…”

“…Transition metal‐based materials such as Fe, Co, Ni, Mn, and Mo oxides/hydroxides and their composites are promising catalysts for various electrochemical reactions, and defects such as anion (O, S, and P) and cation (Fe, Co, and Ni) vacancies could serve as the active sites to promote the electrocatalysis. [ 15–17 ] It is revealed that defects in metal complexes could improve the electrical conductivity, charge redistribution, and optimize their adsorption energy and band structures, [ 18–20 ] thus favorable for various electrochemical reactions. As a booming area, researches on defective transition metal‐based catalysts have received extensive attention.…”

Rare-earth-regulated Ru-O interaction within the pyrochlore ruthenate for electrocatalytic oxygen evolution in acidic media

“…As the ionic radius increased from Yb to Nd, the bond length of Ru-O was elongated, which weakened the bonding strength of Ru-O and resulted in increased defective oxygen concentration. To keep the material electrically neutral, the average valence state of Ru decreased with the increase of defective oxygen [46].…”