Lattice oxygen-mediated ABO3-type NdFeO3 perovskite fabricated over multi-walled CNTs for the O2 evolution reaction and photo-induced degradation of Victoria blue B

Abstract

Hydrogen is generally considered a future sustainable energy carrier, and its electrochemical synthesis is based on the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Nonetheless, a high energy barrier and slow reaction kinetics plague the OER, posing huge obstacles to efficient hydrogen production. In order to address the shortcoming, designing efficient electrocatalysts is essential to enhancing the efficiency and scalability of the OER. On the other hand, the emergence of life-threatening pollutants has pushed researchers towards designing photocatalysts for photo-induced degradation. Therefore, a perovskite (PSK) ABO3-type NdFeO3 was fabricated over multi-walled carbon nanotubes (MWCNTs) to target dual applications of water splitting and photodegradation. Techniques such as XRD, FTIR spectroscopy, SEM, TEM, EDS, PL/UV-vis spectroscopy, TGA, BET, and Raman spectroscopy were used to characterize the nanocomposite. The prepared NdFeO3@MWCNTs showed a direct band gap energy (Eg) of 2.5 eV and an indirect Eg of 1.9 eV as determined through UV-visible spectroscopy. Furthermore, numerous parameters, including catalyst dosage, pollutant concentration, oxidizing agent, and pH, were comprehensively examined for the degradation of Victoria blue B dye. The percentage degradation was found to be optimized for the 250 ppm pollutant solution with 97% removal efficiency within the initial 5 minutes. Furthermore, the electrochemical studies of NdFeO3@MWCNTs showed its potential as an electrocatalyst with an overpotential (η) of 250 mV at a current density of 10 mA cm−2, along with a low Tafel slope of 67 mV dec−1. Moreover, the material showed an electrochemical surface area (ECSA) of 100 cm2 and a decreased charge transfer resistance (Rct) of 1.5 Ω, with the low Rct being ascribed to the faster charge transfer rate. Hence, the low-cost NdFeO3@MWCNTs nanocomposite, compared to noble metal electrodes, is not only a promising photocatalyst but also an electrocatalyst for future applications in H2 generation.