Two-dimensional [Co(btbH)2(dpe)2]·DMF metal–organic framework-derived low-cost nanocomposites for electrochemical nitrate reduction for ammonia production

Abstract

Excess nitrate (NO₃⁻) accumulation occurs due to an imbalanced nitrogen cycle, primarily driven by artificial nitrogen fixation. In the meantime, environmental NO₃⁻ buildup has a substantial adverse effect on human health and the ecosystem. The electrocatalytic nitrate reduction reaction (NO₃RR), which yields value-added compounds like ammonia (NH₃), has lately attracted attention as a viable technique for addressing environmental and energy-related concerns. The NO₃RR meets the urgent need to remove NO₃⁻ and produce NH₃ through an alluring electrocatalytic pathway. Thus, this paper will discuss the preparation of novel 2D [Co(btbH)₂(dpe)₂]·DMF metal–organic frameworks, which crystallize in the triclinic crystal system belonging to the P space group, using a solvothermal method. Among the nanocatalysts used, metallic cobalt nanoparticles supported on nitrogen-doped carbon (CoNPs/NC-600), facilely prepared through the thermal decomposition of Co-MOFs, have been shown to be highly efficient electrocatalysts for NH₃ production from the NO₃RR. The CoNPs/NC-600 nanocomposites exhibit a maximum partial current density (PCD) of −66.03 mA cm⁻² for NH₃ production, achieving a faradaic efficiency (FE) of 72.25% at −0.5 V vs. RHE. Additionally, the highest yield rate of ammonia reached a notable value of 30.79 mmol h⁻² cm⁻². Furthermore, density functional theory (DFT) calculations revealed that the Co[111] surface facilitates active nitrate reduction surpassing water dissociation over the Co₃O₄[311] surface. Hence, this work provides a new design strategy for developing high-performance MOF-derived electrocatalysts for the nitrate reduction reaction (NO₃RR) aimed at NH₃ production.