School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore.
Solar Fuels Laboratory and Energy Research Institute, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore.
Adv Mater. 2019 Oct;31(41):e1902509. doi: 10.1002/adma.201902509. Epub 2019 Jul 30.
The clean energy carrier, hydrogen, if efficiently produced by water electrolysis using renewable energy input, would revolutionize the energy landscape. It is the sluggish oxygen evolution reaction (OER) at the anode of water electrolyzer that limits the overall efficiency. The large spinel oxide family is widely studied due to their low cost and promising OER activity. As the distribution of transition metal (TM) cations in octahedral and tetrahedral site is an important variable controlling the electronic structure of spinel oxides, the TM geometric effect on OER is discussed. The dominant role of octahedral sites is found experimentally and explained by computational studies. The redox-active TM locating at octahedral site guarantees an effective interaction with the oxygen at OER conditions. In addition, the adjacent octahedral centers in spinel act cooperatively in promoting the fast OER kinetics. In remarkable contrast, the isolated tetrahedral TM centers in spinel prohibit the OER mediated by dual-metal sites. Furthermore, various spinel oxides preferentially expose octahedral-occupied cations on the surface, making the octahedral cations easily accessible to the reactants. The future perspectives and challenges in advancing fundamental understanding and developing robust spinel catalysts are discussed.
清洁能源载体氢气，如果能通过使用可再生能源输入的水电解高效生产，将彻底改变能源格局。限制整体效率的是阳极上水分解器中缓慢的氧气析出反应（OER）。由于具有低成本和有前景的 OER 活性，大型尖晶石氧化物家族得到了广泛研究。由于过渡金属（TM）阳离子在八面体和四面体位置的分布是控制尖晶石氧化物电子结构的重要变量，因此讨论了 TM 对 OER 的几何效应。实验发现并通过计算研究解释了八面体位置的主导作用。位于八面体位置的氧化还原活性 TM 保证了与 OER 条件下氧的有效相互作用。此外，尖晶石中相邻的八面体中心协同作用促进了快速的 OER 动力学。相比之下，尖晶石中孤立的四面体 TM 中心会阻碍通过双金属位点进行的 OER。此外，各种尖晶石氧化物优先在表面暴露占据八面体的阳离子，使得八面体阳离子更容易接触反应物。还讨论了在推进基本理解和开发稳健尖晶石催化剂方面的未来展望和挑战。
