Long-term electrocatalytic N2 fixation by MOF-derived Y-stabilized ZrO2: insight into the deactivation mechanism

Abstract

Industrially, NH₃ synthesis is largely dependent on the Haber–Bosch method which consumes a lot of energy and emits huge amounts of CO₂. Recently, the electrochemical N₂ reduction reaction (NRR) has been recognized as a promising method to achieve clean and sustainable NH₃ production, thus highly efficient and durable catalysts are urgently desired. In this paper, we report a MOF-derived carbon/Y-stabilized ZrO₂ nanocomposite (C@YSZ) that works as an efficient electrocatalyst for NRR in 0.1 M Na₂SO₄. It achieves a large NH₃ production of 24.6 μg h⁻¹ mg_cat.⁻¹ and a high faradaic efficiency of 8.2% at −0.5 V vs. the reversible hydrogen electrode. The experimental results demonstrate that the surface oxygen vacancies are the main catalytic sites for NRR. Introducing Y³⁺ into the ZrO₂ lattice has a significant effect to increase and stabilize the O-vacancies. Meanwhile, this catalyst displays remarkable stability and durability for NRR, showing negligible change after 7 days reaction, which is better than most reported NRR electrocatalysts. Moreover, an in situ electrochemical quartz-crystal microbalance (EQCM) was applied in the NRR field for the first time and was successfully combined with density functional theory (DFT) calculations to reveal the deactivation mechanism.