Stabilized PbO2 electrode prepared via crystal facet controlling for outstanding degradation of MePB

Effects of oxygen pressure on the morphology and surface energetics of β-PbO2: insight from DFT calculations

For over a century, lead dioxide (PbO₂) has been investigated in lead-acid batteries and extensively utilized in a variety of applications. Identifying the surface properties and equilibrium morphology of β-PbO₂ (rutile phase) particles is mandatory for industrial utilization and surface engineering. Using density-functional calculations within the generalized gradient approximation revised for solids (PBEsol), we investigate a variety of surface properties of β-PbO₂. The surface energies of low-Miller-index stoichiometric surfaces are firstly determined, and the (110) surface is found to be the most thermodynamically stable. The relative energetics of these surfaces are represented by a Wulff construction which shows an acicular shape, mostly dominated by the (110) and (100) surfaces. Besides, we investigate the surface chemistry of β-PbO₂ under reduction and oxidation conditions as a function of oxygen pressure, finding that most surfaces except for (100) and (110) are likely to be oxidized. Under oxygen pressure at 1 atm and oxygen-rich limit, the (101) surface is the most thermodynamically stable, dominating the Wulff construction with pyramidal shapes. Our results indicate that the growth conditions that cause non-stoichiometry of the surface could modify the equilibrium Wulff shape of β-PbO₂. Our predicted Wulff shapes and dominant facets agree with the experimental results in which the pyramidal shape of the β-PbO₂ grains has often been observed with the (101) preferred orientation.

A closed-loop electrokinetic system for recovery of PbO2@Fe composite derived from lead-containing sludge

Lead-containing sludge produced from lead-acid battery factory will cause environmental hazards if they are not treated properly. A novel process was developed to recycle lead from sludge back into Fe-doped PbO₂ electrodes and realize sludge reduction in this study. The effects of Fenton conditioning on Pb removal efficiency in electro-kinetic (EK) treatment process and its mechanism as well as electro-dewatering (ED) performance were investigated. It was found that the oxidation of Fenton can promote desorption and release of Pb from the organic binding state, and improve the removal efficiency of Pb during EK process, as well as enhance sludge ED performance. About 63.8 wt% Pb can be removed from sludge during EK process, achieving sludge reduction of 63.5 wt% by ED treatment. The composite PbO₂@Fe electrode recovered from lead-containing sludge showed a high electrocatalytic activity for acid red G (ARG) degradation. The electrode obtained by electrodeposition at 20 mA cm^-2 had the largest exchange current density (3.26 × 10^-5 A cm^-2). In the experiment of dye wastewater electrocatalytic degradation, over 99.5% organic matter was degraded within 80 min.

When MXene (Ti3C2Tx) meet Ti/PbO2: An improved electrocatalytic activity and stability

Stable electrode materials with high catalytic activity are urgently required for electrochemical degradation of refractory organic pollutants in wastewater treatment. Herein, high conductive MXene (Ti₃C₂T_x) was firstly fabricated by electrophoretic deposition (EPD) as an interlayer for preparing a novel PbO₂ electrode. The well-conducted Ti₃C₂T_x interlayer significantly improved the electrochemical performance of the EPD-2.0/PbO₂ (EPD time was 2.0 min) electrode with the charge transfer resistance decreased by 9.51 times, the inner active sites increased by 5.21 times and the ∙OH radicals generation ability enhanced by 4.07 times than the control EPD-0/PbO₂ anode. Consequently, the EPD-2.0/PbO₂ electrode achieved nearly 100% basic fuchsin (BF) and 86.78% COD removal efficiency after 3.0 h electrolysis. Therefore, this new PbO₂ electrode presented a promising potential for electrochemical degradation of BF and the new Ti₃C₂T_x middle layer could also be used to fabricate other efficient and stable anodes, such as SnO₂, MnO₂, TiO₂, etc.

Electrocatalysis degradation of coal tar wastewater using a novel hydrophobic benzalacetone modified lead dioxide electrode

Coal tar wastewater is hard to degrade by traditional methods because of its toxic pollutant constituents and high concentration of aromatic hydrocarbons, especially phenolic substances. A new type of hydrophobic benzacetone modified PbO₂ anode (BA-PbO₂ electrodes) was used for the electrocatalytic treatment of coal tar wastewater in a continuous cycle reactor. The surface morphology, structure, valences of elements, hydrophobicity, hydroxyl radical (·OH) produced capacity, electrochemical properties and stability of BA-PbO₂ electrodes were characterized by SEM (scanning electron microscopy), XRD (X-ray diffraction), XPS (X-ray photoelectron spectroscopy), contact angle, a fluorescence probe test, an electrochemical workstation and accelerated life test, respectively. The BA-PbO₂ electrodes exhibited a compact structure and finely dispersed crystallize size of 4.6 nm. The optimum degradation conditions of coal tar wastewater were as follows: current density of 90 mA cm^-2, electrode gap of 1 cm and temperature at 25 °C with flow velocity of 80 L h^-1. The chemical oxygen demand (COD) removal efficiency reached 92.39% after 240 min of degradation under the optimized conditions and the after-treatment COD value was 379.51 mg L^-1 which was lower than the centralized emission standard (less than 400 mg L^-1). These findings demonstrated the feasibility and efficiency of electrocatalytically degrading coal tar wastewater by BA-PbO₂ electrodes. The possible mechanism and pathway for phenol a specific pollutant in coal tar wastewater were investigated by quantum chemistry calculations (Multiwfn) and gas chromatography-mass spectrometry (GC-MS). The toxicity of each intermediate was predicted by the ECOSAR program.