A ( 10 1 ¯ 0 $10\bar{1}0$ )-Orientated ZnO Single Crystal Chem-Voltaic Device Beyond Conventional Fuel Cells

To date, new prototype device for directly converting chemical energy into electricity is still the most important pursuit although various types of fuel cells have been developed/commercialized. In this work, a novel ($10\overline{1}0$) orientated ZnO single crystal device is reported that generates electricity using the usual redox reactions. The principle of the device is similar to that of a photovoltaic device, known as a chem-voltaic device. The air-KBH₄ chem-voltaic device has an open-circuit voltage (V_oc) of 2.14 ± 0.007 mV and a short-circuit current (I_sc) of 1.44 ± 0.007 µA. The V_oc and I_sc increase to 2.24 mV and 2.81 µA, respectively, by preadding H₂O₂. A similar phenomenon is also observed when glucose is used to substitute KBH₄. When KBH₄ or glucose solution is added to the ZnO ($10\overline{1}0$) surface, it reacts with chemisorbed oxygen to produce free electrons. Due to the presence of the spontaneous electric field (E_s) in the polar [0001] azimuth of ZnO, these free electrons move along the [0001] direction, producing an electric current. So chemical energy is converted into electricity. This finding opens up research on the chem-voltaic cell.