Ruddlesden-Popper (RP) perovskite oxides (A n+1 B n O 3n+1 ) are promising air electrodes for solid oxide electrolysis cells (SOECs) due to their excellent electrochemical performance and unique structure. Herein, a method of anionic engineering for the oxygen sites of air electrode materials has been proposed in order to further improve the electrocatalytic activity and thermal stability of La 2 NiO 4+δ (LNO). La 2 NiO 4+δ-x F x (x = 0, 0.05, 0.1, 0.15, denoted as LNOF0, LNOF005, LNOF01, LNOF015) perovskite oxides are synthesized and evaluated as the air electrode for SOECs. Introducing electronegative F − weakens the metal-oxygen bond, optimizes the oxidation environment (e.g., lattice oxygen activity), and improves surface oxygen exchange. The increased ratio of reactive oxygen species accelerates the oxygen evolution reaction (OER) process. Moreover, the polarization resistance of LNOF01 is 33.3 % lower than that of the LNO in the same test condition at 800 °C. The current densities of the full cell prepared using LNOF01 air electrode for CO 2 and H 2 O electrolysis at 800 °C are 1.23 A cm −2 (70 % CO 2 –30 % CO, 1.5 V) and 1.04 A cm −2 (70 % H 2 O-30 % H 2 , 1.3 V), which are enhanced by 25.51 % and 44.44 % compared to the LNO, respectively. In the stability tests, the LNOF01 half-cell maintains stability for more than 170 h at 0.5 A cm −2 and 800 °C, and the full cell tests with the electrolysis of CO 2 and H 2 O maintains stability for more than 50 h at as high as 1 A cm −2 and 800 °C, respectively. This study provides a rational design strategy for constructing high-performance SOECs air electrodes and demonstrates the potential of air electrode anion engineering for SOECs applications.
Ferroelectric tunnel junctions (FTJs) based on ferroelectric switching and quantum tunneling effects with thickness down to a few unit cells have been explored for applications of two-dimensional (2D) electronic devices in data storage and neural networks. As a key performance indicator, the enhanced tunneling electrosistance (TER) ratio provides a broader dynamic range for precise modulation of synaptic weights, improving the stability and accuracy of neural networks. Herein, we report an observation of pronounced enhancement in the TER ratio by over 4 orders of magnitude through the fabrication of large-scale heterostructures combining bismuth ferrite with two-dimensional Ruddlesden–Popper oxide Bi2FeO4. The significant difference in Schottky barrier height between Bi2FeO4 and electrodes leads to a remarkable TER value of 7.8 × 106. Moreover, benefiting from the enhanced conductance contrast between the high resistance state (HRS) and low resistance state (LRS), we demonstrate image recognition and dehaze processing using artificial neural synapses based on these FTJs. These results indicate that giant barrier height modulation can be realized through 2D Ruddlesden–Popper oxides, providing a facile technique for high-density in-memory computing applications.
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