Rowland Institute, Harvard University , Cambridge, Massachusetts 02142, United States.
Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Collaborative Innovation Center of Chemistry for Energy Materials, Department of Chemistry, Fudan University , Shanghai 200433, China.
ACS Nano. 2017 Jun 27;11(6):6451-6458. doi: 10.1021/acsnano.7b03029. Epub 2017 Jun 7.
Engineering active grain boundaries (GBs) in oxide-derived (OD) electrocatalysts is critical to improve the selectivity in CO reduction reaction (CORR), which is becoming an increasingly important pathway for renewable energy storage and usage. Different from traditional in situ electrochemical reduction under CORR conditions, where some metal oxides are converted into active metallic phases but with decreased GB densities, here we introduce the Li electrochemical tuning (LiET) method to controllably reduce the oxide precursors into interconnected ultrasmall metal nanoparticles with enriched GBs. By using ZnO as a case study, we demonstrate that the LiET-Zn with freshly exposed GBs exhibits a CO-to-CO partial current of ∼23 mA cm at an overpotential of -948 mV, representing a 5-fold improvement from the OD-Zn with GBs eliminated during the in situ electro-reduction process. A maximal CO Faradaic efficiency of ∼91.1% is obtained by LiET-Zn on glassy carbon substrate. The CO-to-CO mechanism and interfacial chemistry are further probed at the molecular level by advanced in situ spectroelectrochemical technique, where the reaction intermediate of carboxyl species adsorbed on LiET-Zn surface is revealed.
在氧化物衍生（OD）电催化剂中构建活性晶界（GBs）对于提高 CO 还原反应（CORR）的选择性至关重要，这是可再生能源存储和利用的一个日益重要的途径。与传统的 CORR 条件下的原位电化学还原不同，在这种还原中，一些金属氧化物被转化为活性的金属相，但 GB 密度降低，而我们在这里引入了 Li 电化学调谐（LiET）方法，以可控地将氧化物前体还原为富含 GB 的互连的超小金属纳米颗粒。我们以 ZnO 作为案例研究，证明了具有新暴露的 GB 的 LiET-Zn 在过电势为-948 mV 时表现出约 23 mA cm 的 CO 至 CO 分电流，与在原位电还原过程中消除 GB 的 OD-Zn 相比提高了 5 倍。LiET-Zn 在玻璃碳基底上获得了约 91.1%的最大 CO 法拉第效率。通过先进的原位光谱电化学技术进一步在分子水平上探究了 CO 至 CO 的反应机制和界面化学，揭示了吸附在 LiET-Zn 表面的羧基物种的反应中间体。
