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Low-cost catalysts with high activity are in immediate demand for energy storage and conversion devices. In this study, polyvinyl pyrrolidone was used as a complexing agent to synthesize La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) perovskite oxide. The obtained porous layered LSCF has a large specific surface area of 23.74 m2/g, four times higher than that prepared by the traditional sol-gel method (5.08 m2/g). The oxygen reduction reaction activity of the oxide in 0.1 mol/L KOH solution was studied using a rotating ring-disk electrode. In the tests, the initial potential of 0.88 V (vs. reversible hydrogen electrode) and the limiting diffusion current density of 5.02 mA/cm2 were obtained at 1600 r/min. Therefore, higher catalytic activity and stability were demonstrated, compared with the preparation of LSCF perovskite oxide by the traditional method.

Transition metal phosphide/carbon composites are promising electrocatalysts for oxygen reduction reaction (ORR). Herein, we propose a facile process to fabricate a bayberry-like N, P-enriched carbon nanospheres embedded with Fe2P nanocrystals (Fe2P/NPCs). Bayberry-like polyaniline nanospheres (PANI-NS) are firstly synthesized through microemulsion template method. Then, Fe is incorporated in PANI-NS during the hydrothermal treatment. Lastly FexP nanocrystals and N, P-enriched carbonaceous carriers are obtained by pyrolyzing the hydrothermal-treated PANI-NS. The resultant FexP/NPCs exhibit a uniform particle size (~250 nm), a large specific surface area (523 m2 g−1) and a homogeneous mesoporous structure (~3.46 nm). The phase structure of FexP depends on the Fe/P (molar ratio) during hydrothermal treatment. When Fe/P is around 0.2, a preferable Fe2P phase is obtained. The Fe2P/NPCs exhibit outstanding ORR electrocatalytic activity with a half-wave potential of 0.820 V (vs. RHE) and a diffusion-limited current density of 5.58 mA cm−2, comparable with commercial Pt/C. Moreover, Fe2P/NPCs possess a good duration stability and higher methanol tolerance than commercial Pt/C. When assembled in zinc-air batteries, Fe2P/NPCs contribute to an open circuit voltage of 1.449 V, a maximum power density of 128.38 mW cm−2, and a specific capacity of 691.0 mAh g−1, superior to the commercial Pt/C-based zinc-air battery.

The nonferrous metal electrowinning process is energy intensive due to the sluggish dynamics of the oxygen evolution reaction (OER) on the anode. Developing novel anode materials with high OER activity and stability is imperative. Herein, we propose a novel Pb-ceramic composite anode by introducing ZnFe2O4. In this work, Pb-ZnFe2O4 and PS-Pb anodes were prepared through powder pressing and sintering processes. The effects of ZnFe2O4 particles on the phase composition, surface morphology and inner structure of the oxide layer formed on Pb-ZnFe2O4 anodes were investigated. Furthermore, the role of ZnFe2O4 in the anodic potential and stability of Pb-ZnFe2O4 anodes was discussed. The results show that as the ZnFe2O4 content increases, the oxide layer formed on Pb-ZnFe2O4 anodes exhibits higher surficial compactness, higher integrity, and much smaller thickness. ZnFe2O4 exhibits a trivial impact on the oxygen evolution dynamics. However, the anodic potential of the Pb-ZnFe2O4 anode declines as the ZnFe2O4 content increases, which could be attributed to the higher compactness and smaller thickness of the oxide layer. As the ZnFe2O4 content increases, the weight loss of the Pb-ZnFe2O4 composite anode increases, suggesting the unsatisfactory stability of Pb-ZnFe2O4, which could be attributed to the inevitable dissolution of ZnFe2O4 particles, smaller thickness of the oxide layer and larger porosity of the substrate. Although Pb-ZnFe2O4 composite anodes have the potential to reduce energy consumption, their unsatisfactory stability limits the feasibility of Pb-ZnFe2O4 anodes in the electrowinning industry.

In this work, the surface morphology, inner structure and phase composition of the oxide layers formed on Pb and pyramid-shaped 3D-Pb (Pyra-Pb) anodes after different periods of galvanostatic polarization were investigated. The results showed that in the preliminary stage, the lead compounds and MnO2 deposited at a higher rate on the Pyra-Pb anode. The deposited MnO2 layer on the Pyra-Pb anode was compact and well adhered, while that on the Pb anode exhibited a loose and porous structure. After a longer period of galvanostatic polarization, the oxide layer on the Pyra-Pb anode exhibited a higher stability due to its smaller thickness, denser surface structure and higher physical stability of the inner MnO2 layer. Consequently, the potential-time curve of the Pyra-Pb anode was smooth, while that of the Pb anode presented an oscillatory character with potential spikes and steps. Furthermore, the performance of the Pyra-Pb anode during 72 h of galvanostatic electrolysis was evaluated and compared with that of the Pb anode. The results showed that in the presence of 4 and 6 g L−1 Mn2+, the average anodic potentials of the Pyra-Pb anode were approximately 70 mV and 100 mV lower than those of the Pb anode, respectively. The lower potentials could be explained by the lower ohmic resistance of the MnO2 layer due to its denser structure and smaller thickness. It was also found that the Pyra-Pb anode significantly reduced the mass of the cell sludge, which could be attributed to the higher stability of the MnO2 layer and lower Mn3+ concentration in the electrolyte. In summary, it was demonstrated that the Pyra-Pb anode has a great potential to reduce the energy consumption and cell sludge of the zinc electrowinning process.