Improvement of electrocatalytic performance in MnFeCoNiCu2 high-entropy alloy for urea synthesis by introducing functional graphene quantum dot and copper-rich phase

Abstract

High entropy alloy become an ideal candidate of electrocatalysts because of excellent conductivity, multifunctionality, selectivity and stability. However, poor catalytic performance restricts its wide applications in industrial production. The paper reports one strategy for improvement of electrocatalytic performance in MnFeCoNiCu₂ high-entropy alloy (HEA) nanoparticles for urea synthesis by introducing serine and histidine-functionalized and boron-doped graphene quantum dot (SHB-GQD) and copper-rich phase. The study reveals strong coordination between SHB-GQD and metal ion ensures an uniform distribution of all metal elements at atom level in solution and solid states. The explosion caused by thermal decomposition of SHB-GQD and cotton at high temperature achieves to mild atomization and alloying. The resulted MnFeCoNiCu_2.0HEA shows an irregular spherical shape with small particle size of 125±1.5 nm, double FCC phase and good element homogeneity. The introduction of SHB-GQD and copper-rich phase realizes a significantly improved electrocatalytic activity for urea synthesis. However, the improvement depends on structure of GQD. This gives us one new insight to make various HEA nanomaterials with a desired catalytic performance by rational design of GQD. MnFeCoNiCu₂HEA/SHB-GQD electrocatalyst exhibits high urea yield of 59.01 mmol g^-1 h^-1 with high Faradaic efficiency of 26.6%, which is more than that of reported electrocatalysts.