Ultrasonic treatment-assisted reductive deposition of Cu and Pd nanoparticles on ultrathin 2D Bi2S3 nanosheets for selective electrochemical reduction of CO2 into C2 compounds.

Abstract

In this work, we have ultrasonically deposited Cu and Pd nanoparticles on Bi₂S₃ nanoparticles, prepared using an ultrasonication assisted hydrothermal method. We implemented intense ultrasonic waves bearing frequency of 20 kHz and power of 750 W at the acoustic wavelength of 100 mm to reduce Cu and Pd nanoparticles on the Bi₂S₃ surface. The XRD confirmed the formation of highly crystalline Bi₂S₃ nanoparticles with a pure orthorhombic phase and the deposition of copper (Cu^o) and palladium (Pd^o) nanoparticles was indicated by the strengthening and broadening of the peaks. XPS also confirmed the formation of Cu^o and Pd^o nanoparticles on Bi₂S₃. The Transmission Electron Microscopy (TEM) also exhibited the deposition of Cu and Pd nanoparticles on the Bi₂S₃ nanosheets which was further confirmed using high resolution TEM analysis. The electrochemical CO₂ reduction by Cu-Pd/Bi₂S₃ electrocatalyst using Cu foam as the conducting support led to the formation of acetaldehyde and ethylene as the major products. The rate of formation of ethylene was found to be 488.5 μ mol g^-1h^-1 at an applied potential of -0.6 V (vs. RHE), with the best Faradaic efficiency of 57.09 % at -0.4 V (vs. RHE). Among the liquid phase products, acetaldehyde was the major product showing the maximum Faradaic efficiency of 6.473 % at -0.2 V (vs. RHE), with a total formation rate of 64.27 μ mol g^-1h^-1. The results revealed that the Cu-Pd/Bi₂S₃ electrocatalyst was more selective to C₂ products while the pure Bi₂S₃ nanoparticles majorly produced C₁ compounds.