Enhancing photocatalytic, photoelectrochemical hydrogen evolution, and dye degradation using p-type NiCo2O4 spinel photocatalyst synthesized via tapioca leaf extract mediated process

Abstract

The new energetic material is a matter of concern to overcome the environment and energy crisis. The photocatalytic efficiency of NiCo2O4 prepared via tapioca-leaf extract (NiCoO@TaL) mediated process for environment and energy application are explored in the present work. There was a significant improvement in the photocatalytic hydrogen evolution performance of NiCoO@TaL (1823 umol g−1h−1) compared to the NiCoO@TaL in the absence of Triethanolamine (TEOA, 1052 umol g−1h−1) and simple physical mixture NiCoO-Phy (526 umolg−1h−1. The photoelectrochemical performance of NiCoO@TaL and NiCoO-phy was 0.75 mAcm−2 and 0.55 mA/cm−2 concerning the photocurrent measurements. The photoelectrochemical hydrogen evolution was governed by the participation of electrons and holes aided by the presence of oxygen, which was proved by the deflation of energy levels in the semiconducting photocatalyst and consequent drift in the Fermi energy upon illumination as studied by open circuit potential (OCP) analysis. NiCoO@TaL was robust enough to degrade both cationic [Methylene blue (MB, 82.2 ± 1.0, n = 3) and malachite green (MGr, 83.5 ± 1.9, n = 3)] and anionic [methyl orange (MOr, 99.0 ± 1.3, n = 3) and alizarin red S (ArS, 91.9 ± 1.6, n = 3)] dyes, but showing highest affinity for the degradation of anionic dye MOr. The band structure and charge carrier recombination properties were superior in the case of NiCoO@TaL (4.8 ns). Higher retention of photo-stimulated electrons in the conduction band has enhanced the hydrogen evolution performance, as evident from the time-resolved photoluminescence studies (TRPL). The photocatalyst was remarkably stable, non-toxic, and highly capable after eight cycles of reuse, which makes NiCoO@TaL a potential candidate in the field of photocatalysis.