An electrochemical reaction refers to a process of chemical changes caused by the electrical current, or a process of generating electricity by chemical reactions, in which direction and rate of the reaction can be controlled by electrode potential (
i.e. energy of holes and electrons in the electrode). Because an electrochemical reaction involves with charge transfer across an electrode/electrolyte interface (though it may not be the only process), the reaction kinetics is determined to a large extent by the electronic structures (
i.e. energy level distribution and electronic occupation) of the electrode material and the redox species in the electrolyte. In this talk, we propose a new approach exploiting the
field effect, in addition to electrode potential,
to modulate the electronic structures and electrochemical reaction kinetics at electrode/electrolyte interfaces.
As a model system, we prepared working electrodes with â??gate-insulator-semiconductorâ?? structure, which is similar to that of field effect transistors (FETs). Herein, we employed ultrathin semiconductor layers so that electrochemistry at the semiconductor surface are effectively modulated by a voltage bias applied to the gate. On those gate-tunable electrodes, we observed continuous, in-situ modulation of outer-sphere electron transfer kinetics at the semiconductor/electrolyte interface with voltage biases applied to the gate. For example, the reduction potential of 2,3,5,6-tetrabromo-1,4-benzoquinone (TBBQ) on a 5 nm thick ZnO electrode could be shifted by ~0.4 V. With further control experiments, we found that the observed gate-controlled redox reaction kinetics is essentially attributed to band alignment shift at the electrode/electrolyte interface.
