Mechanistic insight into the synergetic catalytic effect of Pd and MnO 2 for high-performance Li–O 2 cells
Mechanistic insight into the synergetic catalytic effect of Pd and MnO 2 for high-performance Li–O 2 cells
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DOI：
10.1016/j.ensm.2017.11.009
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发表时间：
2018-05
影响因子：
20.4
通讯作者：
Cao Can;Zhenyun Lan;Yucong Yan;Hao Cheng;Bin Pan;Jian Xie;Yunhao Lu;Hui Zhang;Shichao Zhang-Shichao
中科院分区：
文献类型：
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作者：
Cao Can;Zhenyun Lan;Yucong Yan;Hao Cheng;Bin Pan;Jian Xie;Yunhao Lu;Hui Zhang;Shichao Zhang-Shichao
尽管贵金属、金属氧化物及其组合是Li−O2电池研究最多的催化剂，但它们本质上的协同催化机制尚不清楚。在这里，制备并研究了由二维（2D）δ-MnO2纳米片和Pd纳米晶体（NC）组成的混合纳米结构，作为Li−O2电池的有前途的催化剂。采用 Pd/δ-MnO2 混合催化剂的 Li−O2 电池表现出低极化（在 1600 mA g−1 时终端充电/放电电压为 4.2 V/2.58 V）、良好的倍率性能（在 1600 mA g−1 高电流密度下为 2400 mAh g−1）和长循环寿命（133 个循环/247 个循环，容量有限） 1000 mAh g−1/500 mAh g−1) 由于 δ-MnO2 和 Pd 之间的协同催化作用。密度泛函理论 (DFT) 计算表明，δ-MnO2 和 Pd 之间的电荷转移是其协同催化机制的基础，其中 δ-MnO2 片一侧 Pd 的存在促进了 δ-MnO2 片另一侧 Li2O2 的形成。 DFT 计算还表明，在 Pd 位于另一侧的 δ-MnO2 片上形成稳定的电子导电 LiO2 在能量上是可能的。这项工作从机理上深入了解了贵金属和金属氧化物之间的协同催化效应，并为设计高性能催化剂（尤其是二维构型）提供了有效的策略。
Although noble metals, metal oxides and their combinations are the most studied catalysts for Li−O2cells, it is unclear yet about their intrinsically synergetic catalytic mechanism. Here, a hybrid nanostructure composed of two-dimensional (2D) δ-MnO2nanosheets and Pd nanocrystals (NCs) was prepared and investigated as a promising catalyst for Li−O2cells. Li−O2cells with the Pd/δ-MnO2hybrid catalyst exhibit low polarization (terminal charge/discharge voltages 4.2 V/2.58 V at 1600 mA g−1), good rate capability (2400 mAh g−1at a high current density of 1600 mA g−1), and long cycle life (133 cycles/247 cycles with limited capacities of 1000 mAh g−1/500 mAh g−1) due to the synergetic catalytic effect between δ-MnO2and Pd. Density functional theory (DFT) calculations clarify that the charge transfer between δ-MnO2and Pd underlies their synergetic catalytic mechanism, where the presence of Pd on the one side of δ-MnO2sheets facilitates the formation of Li2O2on the opposite side of the δ-MnO2sheets. The DFT calculations also indicate that it is energetically possible for the formation of stable, electronically conductive LiO2on the δ-MnO2sheets with Pd on the opposite side. This work gives a mechanistic insight into the synergetic catalytic effect between noble metal and metal oxide, and provides an effective strategy for designing high-performance catalysts especially with a 2D configuration.