Pd Nanoparticle-Decorated Novel Ternary Bi2O2CO3-Bi2MoO6- CuO Heterojunction for Enhanced Photo-electrocatalytic Ethanol Oxidation

Recently, photo-electrooxidation of fuel using a noblemetal-semiconductorjunction has been one of the most promising approaches in fuel cellsystems. Herein, we report the development of a Pd-supported Bi2MoO6-Bi2O2CO3-CuOnovel ternary heterojunction for ethanol oxidation in alkali in thepresence and absence of visible light. Various spectroscopic and microscopiccharacterization techniques confirm strong coupling between palladiumnanoparticles and Bi2MoO6-Bi2O2CO3-CuO ternary heterojunction supports. The photo-electrocatalyticefficacy of the synthesized catalysts was inspected by cyclic voltammetry(CV), chronoamperometry (CA), and electrochemical impedance spectroscopy(EIS). The CV study reveals that the forward peak current density(in mA mg(-1) of Pd) of the synthesized quaternaryheterojunction was about 1482.5, which is 2.4, 4, and 4.6 times higherthan that of Pd/CuO (608.3), Pd/Bi2MoO6-Bi2O2CO3 (368.3), and similarly synthesizedPd catalyst (321.5) under visible light radiation. The best heterojunctioncatalyst shows 2.21-fold higher peak current density in visible lightcompared to that in dark. CA study reveals that after operation for6000 s, the current density of the quaternary electrode is 1.5 and3.4 times greater than that of Pd/CuO and Pd/C catalysts, respectively.The greater photocurrent response, lower photoluminescence (PL) emissionintensity, and smaller semicircle arc in the Nyquist plot of the quaternarycatalyst demonstrate the efficient segregation and higher charge transferconductance of photogenerated charges to facilitate the photo-electrooxidationprocess of ethanol. The stability test shows that the quaternary catalystloses only 9.8 and 7.7% of its maximum current density after 500 cyclesof CV operation in the dark and light, respectively, indicating thatlight energy is more beneficial in establishing high stability. Thedramatic enhancement of the photo-electrocatalytic activity of thequaternary electrode is owing to the lower band gap, high ECSA, enhancedcharge separation of photogenerated carriers (e(-)-h(+)), and all cocatalytic support of Bi2MoO6, Bi2O2CO3, and CuOin Pd/ Bi2MoO6-Bi2O2CO3-CuO under visible light radiation. The morphology and structureof the used quaternary catalyst are tested using FESEM and PXRD. Finally,ex situ FTIR spectroscopy and HPLC techniques help understand theethanol electrooxidation reaction mechanism.