Oxygen-Bridged Vanadium Single-Atom Dimer Catalysts Promoting High Faradaic Efficiency of Ammonia Electrosynthesis

Abstract

Single-atom catalysts have already been widely investigated for the nitrogen reduction reaction (NRR). However, the simplicity of a single atom as an active center encounters the challenge of modulating the multiple reaction intermediates during the NRR process. Moving toward the single-atom-dimer (SAD) structures can not only buffer the multiple reaction intermediates but also provide a strategy to modify the electronic structure and environment of the catalysts. Here, a structure of a vanadium SAD (V-O-V) catalyst on N-doped carbon (O-V 2 -NC) is proposed for the electrochemical nitrogen reduction reaction, in which the vanadium dimer is coordinated with nitrogen and simultaneously bridged by one oxygen. The oxygen-bridged metal atom dimer that has more electron deficiency is perceived to be the active center for nitrogen reduction. A loop evolution of the intermediate structure was found during the theoretical process simulated by density functional theory (DFT) calculation. The active center V-O-V breaks down to V-O and V during the protonation process and regenerates to the original V-O-V structure after releasing all the nitrogen species. Thus, the O-V 2 -NC structure presents excellent activity toward the electrochemical NRR, achieving an outstanding faradaic efficiency (77%) along with the yield of 9.97 μg h −1 mg −1 at 0 V (vs RHE) and comparably high ammonia yield (26 μg h −1 mg −1 ) with the FE of 4.6% at −0.4 V (vs RHE). This report synthesizes and proves the peculiar V-O-V dimer structure experimentally, which also contributes to the library of SAD catalysts with superior performance.

C─N Coupling Enabled by N─N Bond Breaking for Electrochemical Urea Production

“…Previous experimental studies on systems such as diatomic Zn─Mn sites, [17] NiFe─DAC, [23] PdCu/NC, [24] Ni dual-atom sites, [25] O─V 2 ─NC, [26] Zn/Fe─N─C, [27] and FeMoN 6 [28] have demonstrated the viability of diverse electrocatalytic reactions. Based on the evaluation of thermodynamic and electrochemical stabilities, we thus believe that V 2 N 6 DAC is feasible for enabling the electrocatalytic conversion of N 2 and CO into urea.…”

Atomically‐Dispersed Metal Heterocatalysts: A Practical Step Toward Sustainability

“…In this type of catalyst, there is a spatial correlation among the metal single‐atom sites with or without a bridging atom. Correlated SAC having two metal centers are called dual‐atom (also known as double‐atom) catalysts [72–74] . Dual‐atom catalysts (DACs) are introduced in different modes such as two separated heterometallic sites, two linked homometallic sites and two linked heterometallic sites [75] .…”

“…Correlated SAC having two metal centers are called dualatom (also known as double-atom) catalysts. [72][73][74] Dual-atom catalysts (DACs) are introduced in different modes such as two separated heterometallic sites, two linked homometallic sites and two linked heterometallic sites. [75] Each of them has its own electronic characteristics and properties.…”

Recent Developments of Dual Single‐Atom Catalysts for Nitrogen Reduction Reaction

“…The OÀ V 2 À NC demonstrates an impressive FE of 77 % for NH 3 production, achieving a yield of 9.97 μg h À 1 mg À 1 at 0 V vs RHE. [14] Herein, we summarize the structures and activities of different reported DSACs in ENRR. According to the distance of two metal atoms, the DSACs can be divided into adjacent DSACs and DSACs dimer.…”

“…Ru@ZrO 2 /NC [22] 3.7 mgh À 1 mg Ru À 1 ~21 % OÀ V 2 À NC [14] 26.1 μg h À 1 mg À 1 77.2 % VPC-NC 12.5 μg h À 1 mg À 1 ~70 % PdPb/C [23] 37.68 μg mg À 1 cat h À 1 , 7.54 μg cm À 2 h À 1 5.79 % Pd/C 4.8 μg mg À 1 cat h À 1 0.15 % Fe, MoÀ N/C [24] 1.52×10 À 6 mol h Fe, Pt, Ni, FeNi [26] 1.33×10 À 12 À 3.80×10 À 12 mol/kg 1.1-41 % Cd/In 2 O 3 (V O ) [27] 57.5 μg h À 1 mg cat…”