Electrocatalytic degradation of methyl orange and 4-nitrophenol on a Ti/TiO-NTA/La-PbO electrode: electrode characterization and operating parameters.

The anode material plays a crucial role in the process of electrochemical oxidation. Herein, a TiO nanotube arrays (TiO-NTA) intermediate layer and La-PbO catalytic layer were synthesized on a Ti surface by the electrochemical anodic oxidation and electrochemical deposition technology, respectively. The prepared Ti/TiO-NTA/La-PbO electrode was used as an electrocatalytic oxidation anode for pollutant degradation. Scanning electron microscopy (SEM) analysis showed that the TiO-NTA layer possessed a highly ordered and well-aligned nanotube array morphology, and the La-PbO layer with angular cone cluster was uniform and tightly bonded. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis indicated that the intermediate layer primarily consisted of the anatase crystal structure of TiO and the catalyst layer was made of La-PbO. Electrochemical analysis revealed that Ti/TiO-NTA/La-PbO electrode exhibited higher oxidation peak current, electrochemical active surface area, and oxygen evolution potential (OEP, 1.64 V). Using methyl orange and 4-nitrophenol as model pollutants, electrocatalytic properties of the prepared Ti/TiO-NTA/La-PbO electrode were systematically investigated under different conditions, and the electrochemical degradation fitted well with the pseudo-first-order kinetics model. Efficient anodic oxidation of model pollutants was mainly attributed to the indirect oxidation mediated by hydroxyl radicals (•OH). The total organic carbon (TOC) removal efficiency of methyl orange and 4-nitrophenol was 70.2 and 72.8%, and low energy consumption (2.50 and 1.89 kWh g) was achieved after 240 min of electrolysis under the conditions of initial concentration of model pollutant, electrode spacing, and electrolyte concentration were 50 mg L, 2 cm, and 0.1 mol L, respectively. This work provided a new strategy to develop the high-efficiency electrode for refractory pollutants degradation.