Zhang Xiaoping, Dong Chung-Li, Wang Yiqing, Chen Jie, Arul Kumaravelu Thanigai, Diao Zhidan, Fu Yanming, Li Mingtao, Shen Shaohua
International Research Center for Renewable Energy, State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China.
Department of Physics, Tamkang University, 151 Yingzhuan Road, New Taipei City 25137, Taiwan.
ACS Appl Mater Interfaces. 2020 Dec 23;12(51):57038-57046. doi: 10.1021/acsami.0c16659. Epub 2020 Dec 10.
Single-component transition-metal oxide (TMO: FeO, NiO, or CoO) nanosheets grown on nickel foam (NF) were electrochemically optimized with Li ion (Na ion)-induced conversion reaction for bifunctional electrocatalysis. The optimum FeO/NF-Li electrocatalyst exhibits low overpotentials of 239 mV for hydrogen evolution reaction and 276 mV for oxygen evolution reaction at a current density of 100 mA cm. A two-electrode water splitting cell using FeO/NF-Li as both anode and cathode requires only 1.60 V to achieve a current density of 10 mA cm. The impressive water splitting performance of the FeO/NF-Li electrode is revealed to be attributed to Li-induced electrochemical conversion, which alters the crystal structure, creating more active sites for electrocatalytic reactions, as well as introduces O vacancies increasing the electron density and the intrinsic conductivity. More importantly, the atomic arrangement is regulated from tetrahedral Fe(Td) to octahedral Fe(Oh) coordination, which acts as catalytically active sites with reduced Gibbs free energy for the rate-determining steps. This electrochemical conversion reaction can be extended to other TMOs (i.e., NiO/NF and CoO/NF) for promoted electrocatalytic water splitting performances. This study provides an in-depth understanding on the nature of atomic and electronic structure evolution to promote the electrocatalytic activity.
在泡沫镍（NF）上生长的单组分过渡金属氧化物（TMO：FeO、NiO或CoO）纳米片通过锂离子（钠离子）诱导的转化反应进行电化学优化，用于双功能电催化。最佳的FeO/NF-Li电催化剂在100 mA cm的电流密度下，析氢反应的过电位低至239 mV，析氧反应的过电位低至276 mV。使用FeO/NF-Li作为阳极和阴极的双电极水分解电池仅需1.60 V就能达到10 mA cm的电流密度。FeO/NF-Li电极令人印象深刻的水分解性能被揭示归因于锂诱导的电化学转化，这种转化改变了晶体结构，为电催化反应创造了更多活性位点，同时引入氧空位增加了电子密度和本征电导率。更重要的是，原子排列从四面体Fe（Td）配位调节为八面体Fe（Oh）配位，这作为速率决定步骤中具有降低吉布斯自由能的催化活性位点。这种电化学转化反应可以扩展到其他TMO（即NiO/NF和CoO/NF），以提高电催化水分解性能。这项研究为促进电催化活性的原子和电子结构演化的本质提供了深入理解。
