Solar Photoelectroreduction of Nitrate Ions on PbI2/CuI Nanocomposite Electrodes

Abstract

Solar light–driven photoelectrochemical conversion of nitrate ions to nitrite is achieved on copper-lead iodide nanocomposite electrodes. By optimizing the composition, 1.2 ± 0.05 mA cm−2 photocurrent density is obtained under concentrated solar irradiation. The reduction products are NO2− and N2, at 0.61 V reversible hydrogen electrode (RHE), which is at least 600 mV higher than the redox potential of these processes. The faradaic efficiency of NO2− ion formation is up to 52% while no hydrogen evolution occurs. Optical studies show the possibility of exciting electrons from the valence band of CuI to the conduction band of PbI2 upon illumination, extending the visible light absorption of the nanocomposite photoelectrode. Experimental and theoretical optoelectronic studies indicate that CuI and PbI2 are held together by weak attractive forces (also excluding the formation of a new compound), which opens a new strategy to design metal halide nanocomposite photoelectrodes with tailored properties.