Wang Yuxin, Wang Yan, Frisbie C Daniel
Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States.
Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Avenue SE, Minneapolis, Minnesota 55455, United States.
ACS Appl Mater Interfaces. 2023 Feb 13. doi: 10.1021/acsami.2c18549.
We report steady-state voltammetry of outer-sphere redox species at back-gated ultrathin ZnO working electrodes in order to determine electron transfer rate constants as a function of independently controlled gate bias, . We demonstrate that can be modulated as much as 30-fold by application of ≤ 8 V. The key to this demonstration was integrating the ultrathin (5 nm) ZnO on a high dielectric constant (k) insulator, HfO (30 nm), which was grown on a Pd metal gate. The high-k HfO dramatically decreased the required values and increased the gate-induced charge in ZnO compared to previous studies. Importantly, the enhanced gating power of the Pd/HfO/ZnO stack meant it was possible to observe a nonmonotonic dependence of on , which reflects the inherent density of redox acceptor states in solution. This work adds to the growing body of literature demonstrating that electrochemical kinetics (i.e., rate constants and overpotentials) at ultrathin working electrodes can be tuned by , independent of the conventional electrochemical working electrode potential.
我们报告了背栅超薄ZnO工作电极上外层氧化还原物种的稳态伏安法，以确定电子转移速率常数作为独立控制的栅极偏置的函数。我们证明，通过施加≤8 V的电压，电子转移速率常数可调节多达30倍。这一证明的关键在于将超薄（5 nm）ZnO集成在高介电常数（k）绝缘体HfO₂（30 nm）上，该绝缘体生长在Pd金属栅极上。与先前的研究相比，高k值的HfO₂显著降低了所需的栅极电压值，并增加了ZnO中的栅极感应电荷。重要的是，Pd/HfO₂/ZnO堆叠结构增强的栅控能力意味着有可能观察到电子转移速率常数对栅极电压的非单调依赖性，这反映了溶液中氧化还原受体态的固有密度。这项工作增加了越来越多的文献，表明超薄工作电极上的电化学动力学（即速率常数和过电位）可以通过栅极电压进行调节，而与传统电化学工作电极电位无关。
