Synthesis of AuCu nanoalloy and investigation on its electrocatalytic proton reduction and CO2 reduction activity

Tóm tắt

Identifying efficient catalysts for the H₂ evolution reaction and CO₂ reduction, which can operate at low overpotential in a neutral or near-neutral pH aqueous solution, represents a significant challenge. This work reports the synthesis of an AuCu nanoalloy in the form of spherical nanoparticles with an average size of ~16.7±0.3 nm. The morphology, crystal structure, and chemical composition of AuCu nanoparticles were characterised by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution - high angle annular dark field - scanning transmission electron microscopy (HR-HAADF-STEM), and energy dispersive X-ray (EDX) analysis. The use of AuCu nanoparticles as a catalyst for the H₂ evolution and CO₂ reduction reactions in a 0.1 M KHCO₃ (pH 6.8) solution was investigated. It was found that AuCu nanoparticles catalysed the reduction of CO₂ to CH4 at a low cathodic potential of -0.2 V vs. Reversible hydrogen electrode (RHE) with a Faradaic efficiency of 7.1%. However, at low cathodic potentials ranging from -0.2 to -0.5 V vs. RHE, H₂ evolution was more favourable than CO₂ reduction reactions. Conversely, at higher cathodic potentials, e.g. -0.6 V vs. RHE, the reduction of CO₂ to CO was more favourable. The AuCu nanoparticles demonstrate superior CO₂ reduction selectivity compared to Au and Cu nanoparticle catalysts. A discussion on potential reaction pathways contributing to the CO₂ reduction selectivity is also proposed.