CeFEMA, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisbon, Portugal.
Phys Chem Chem Phys. 2018 Jul 18;20(28):19045-19056. doi: 10.1039/c8cp02114g.
Typical direct liquid fuel cells (DLFCs) use a liquid fuel and O2 as the oxidant. However, for applications where O2 is not available (e.g., space and underwater), the gas has been replaced by H2O2 as a liquid oxidant. This work presents a study of various ceramic disc electrodes with K2NiO4 structure and nominal compositions La2NiO4, La2CuO4, La1.9Pr0.1CuO4, La1.9Sr0.1CuO4, La1.8Ce0.2NiO4, La1.9Pr0.1NiO4, La1.8Pr0.2NiO4 and La1.9Sr0.1NiO4 to assess their stability and activity for the hydrogen peroxide reduction reaction (HPRR) in alkaline media. Stability tests conducted in 2 M NaOH show that Ni and Cu are readily dissolved, as occurs for substituting elements such as Sr, in agreement with calculated Pourbaix diagrams. Such degradation affects the surface of the materials, which is depleted of transition metals. This has consequences for the ORR and HPRR activity due to formation of a La-rich passivation layer on the surface. Only La2CuO4 and La1.8Ce0.2NiO4 display HPRR activity at around -0.25 V vs. RHE. An attempt is made to correlate the composition, chemical stability and electrochemical behaviour of these materials based on known molecular-orbital models proposed for the oxygen reduction reaction.
典型的直接液体燃料电池（DLFC）使用液体燃料和 O2 作为氧化剂。然而，对于 O2 不可用的应用（例如太空和水下），气体已被 H2O2 作为液体氧化剂取代。这项工作研究了各种具有 K2NiO4 结构和标称组成 La2NiO4、La2CuO4、La1.9Pr0.1CuO4、La1.9Sr0.1CuO4、La1.8Ce0.2NiO4、La1.9Pr0.1NiO4、La1.8Pr0.2NiO4 和 La1.9Sr0.1NiO4 的陶瓷圆盘电极，以评估它们在碱性介质中用于过氧化氢还原反应（HPRR）的稳定性和活性。在 2 M NaOH 中进行的稳定性测试表明，Ni 和 Cu 很容易溶解，就像 Sr 等取代元素一样，这与计算的 Pourbaix 图一致。这种降解会影响材料的表面，使过渡金属耗尽。这对 ORR 和 HPRR 活性有影响，因为表面形成了富含 La 的钝化层。只有 La2CuO4 和 La1.8Ce0.2NiO4 在相对于 RHE 的约-0.25 V 下显示出 HPRR 活性。尝试基于为氧还原反应提出的已知分子轨道模型，根据这些材料的组成、化学稳定性和电化学行为进行关联。
