This reaction leads to the gradual dissolution of NiO/Ni(OH)2, rendering it unstable under acidic conditions and reducing the voltage window for this composite. It is also important to note that free-standing electrodes are not ideal because the combined conductive additives such as carbon nanotubes (CNTs) or carbon black may also electrosorb ions under blocked polarization leading to a capacitive contribution to the current response and decreasing the rectification ability of the designed devices.