Electrochemical oxygen reduction and oxygen evolution are two key processes that limit the efficiency of important energy conversion devices such as metal–air battery and electrolysis. Perovskite oxides are receiving discernable attention as potential bifunctional oxygen electrocatalysts to replace precious metals because of their low cost, good activity, and versatility. In this review, we provide a brief summary on the fundamentals of perovskite oxygen electrocatalysts and a detailed discussion on emerging high-performance oxygen electrocatalysts based on perovskite, which include perovskite with a controlled composition, perovskite with high surface area, and perovskite composites. Challenges and outlooks in the further development of perovskite oxygen electrocatalysts are also presented.

This study investigated the electrochemical actuation behavior of nanoporous material during the capacitive process. The length change of nanoporous gold (npg) was in situ investigated in a liquid environment using the dilatometry technique. The mechanical effect of MnO2 layers was introduced in this work to improve the actuation characteristics of the npg samples. Our work found that the actuation behavior of npg sample could be significantly modulated with a covering of MnO2 layers. The electrochemical actuation amplitude was efficiently improved and strongly dependent on the thickness of MnO2 layers covered. Aside from the amplitude, the phase relation between the length change and the electrode potential was inverted when covering the MnO2 layer on the npg samples. This means the expansion of the npg samples and the contraction of samples covered with the MnO2 layer when electrochemical potential sweeps positively. A simple finite element model was built up to understand the effect of the MnO2 layer. The agreement between the simulation result and the experimental data indicates that the sign-inverted actuation-potential response of nanoporous gold contributes to the mechanical effect of MnO2. It is believed that our work could offer a deep understanding on the effect of the MnO2 layer on the electrochemical actuation and then provide a useful strategy to modulate the actuation performance of nanoporous metal materials.

This work investigates the effect of a magnetic field on the electrochemical performance of nanoporous nickel (np-Ni). We first compare the electrochemical capacitance of np-Ni electrodes, which were prepared using the chemical dealloying strategy under different magnetic flux densities (B = 0, 500 mT). Our experimental data show that np-Ni500 prepared under an external magnetic field of 500 mT exhibits a much better electrochemical performance, in comparison with that (np-Ni0) prepared without applying a magnetic field. Furthermore, the specific capacitance of the np-Ni0 electrode could be further enhanced when we increase the magnetic flux densities from 0 T to 500 mT, whereas the np-Ni500 electrode exhibits a stable electrochemical performance under different magnetic flux densities (B = 0 mT, 300 mT, 500 mT). This could be attributed to the change in the electrochemical impedance of the np-Ni0 electrode induced by an external magnetic field. Our work thus offers an alternative method to enhance the electrochemical energy storage of materials.