ZnO Quantum Dots Coupled with Graphene toward Electrocatalytic N₂ Reduction: Experimental and DFT Investigations

Abstract

Electrochemical reduction of N2 to NH3 is a promising method for artificial N2 fixation, but it requires efficient and robust electrocatalysts to boost the N2 reduction reaction (NRR). Herein, a combination of experimental measurements and theoretical calculations revealed that a hybrid material in which ZnO quantum dots (QDs) are supported on reduced graphene oxide (ZnO/RGO) is a highly active and stable catalyst for NRR under ambient conditions. Experimentally, ZnO/RGO was confirmed to favor N2 adsorption due to the largely exposed active sites of ultrafine ZnO QDs. DFT calculations disclosed that the electronic coupling of ZnO with RGO resulted in a considerably reduced activation‐energy barrier for stabilization of *N2H, which is the rate‐limiting step of the NRR. Consequently, ZnO/RGO delivered an NH3 yield of 17.7 μg h−1 mg−1 and a Faradaic efficiency of 6.4 % in 0.1 m Na2SO4 at −0.65 V (vs. RHE), which compare favorably to those of most of the reported NRR catalysts and thus demonstrate the feasibility of ZnO/RGO for electrocatalytic N2 fixation.

Nitrogen‐Doped NiO Nanosheet Array for Boosted Electrocatalytic N2 Reduction

“…Therefore, it is urgently required to explore energy-saving, yet efficient technological routes for artificial N 2 fixation.Electrochemical NH 3 synthesis (N 2 + 3H 2 O!2NH 3 + 3/2O 2 ), derived from N 2 and H 2 O and powered by renewable electricity, provides a sustainable and scalable approach for N 2 fixation at ambient conditions [3][4][5][6][7] . To achieve favorable N 2 -to-NH 3 conversion, a prerequisite is to develop highly active and robust electrocatalysts that can effectively activate N 2 reduction reaction (NRR) and realize both high NH 3 yield and Faradaic efficiency (FE) at relatively low potentials [8][9][10][11] . Precious metalbased catalysts (Ru [12] and Au [13] ) have been reported to be highly efficient in NRR, but the scarcity and high cost make them impractical for large scale utilization.…”

Exploration and Investigation of Periodic Elements for Electrocatalytic Nitrogen Reduction

“…Zinc was explored as NRR catalyst in the form of ZnO quantum dots supported on rGO, which turned out be very stable and active for N 2 fixation. [240] At −0.65 V, ZnO/rGO harvested NH 3 at 17.7 µg h −1 mg cat −1 rate with 6.4% efficiency. The electrochemical reaction was carried out in 0.1 m H 2 SO 4 .…”

Recent Advances in the Application of Structural‐Phase Engineering Strategies in Electrochemical Nitrogen Reduction Reaction

“…[73] The presence of Sb 0 significantly increases the exposure of SbPO 4 , and this has a positive impact on NRR performance, resulting in Faraday efficiencies of up to 34%. Liu et al [74] loaded ZnO quantum dots on rGO; in this material, the OH group on rGO plays a bridging role in promoting the electronic interaction between graphene and ZnO and achieving effective electron transfer during NRR. Therefore, ZnO/rGO delivered an NH 3 yield of 17.7 µg h −1 mg −1 and a Faradaic efficiency of 6.4% in 0.1 m Na 2 SO 4 at −0.65 V versus RHE.…”