Strongly coordinated synthesis of high-loading Ta2O5-supported Ru-Fe-Ni single-atom electrocatalyst with enhanced catalytic performance for urea synthesis via multifunctional graphene quantum dot integration

Abstract

Industrial application of oxide-supported single atom catalysts remains many challenges, including poor economic feasibility, insufficient catalytic activity, limited electrical conductivity, and lack of functional diversity. The study reports a coordination-driven synthesis strategy for fabricating tantalum pentoxide-supported ruthenium‑iron‑nickel single atom electrocatalyst (Ru-Fe-Ni/Ta₂O₅@DHB-GQD) through metal ion coordination with aspartic acid and histidine-functionalized boron-doped graphene quantum dot (DHB-GQD), followed by controlled annealing. The resulting Ru-Fe-Ni/ Ta₂O₅@DHB-GQD offers atomic dispersion of Ru, Fe, and Ni on Ta₂O₅ with high metal loading of 5.6 wt%. Ta₂O₅ substrate features unique shear-structure with interconnected tunnels, enabling catalytic reactions to proceed simultaneously on the nanocrystal surfaces and within tunnel walls. Integration of DHB-GQD with Ru, Fe and Ni optimizes tunnel structure, reduces bandgap by 0.8 eV, and establishes efficient electron transfer pathways. Compared to pristine Ta₂O₅, engineered catalyst exhibits an enhancement in electrochemical active surface area (>4-fold), electrical conductivity (>53-fold), and K⁺ diffusion efficiency (>1564-fold). Experimental analyses coupled with density functional theory calculation demonstrates that trimetallic synergy of Ru, Fe and Ni significantly improves the catalytic activity and selectivity for reduction of NO₃⁻ and CO₂ into urea. The Ru-Fe-Ni/ Ta₂O₅@DHB-GQD electrocatalyst achieves urea yield of 73.86 mmol g⁻¹ h⁻¹ with Faradaic efficiency of 48.5 %, surpassing previously reported counterparts.