The N-type enhancement mode MOSFETs it uses require a positive gate-to-source voltage to turn on, and are turned off by pulling the gate-to-source voltage down

The N-type enhancement mode MOSFETs it uses require a positive gate-to-source voltage to turn on, and are turned off by pulling the gate-to-source voltage down to 0v. The gate itself forms a capacitor which must be charged to allow the gate-to-source voltage to increase and the MOSFET to turn on. Running a higher voltage than the standard 5v (SOT-23 small signal MOSFETs often can handle 20vgs, depending on the specific part) would allow the gate capacitance to charge much faster and the MOSFETs to turn on much faster. However, the clock speed will still be limited by how quickly that gate charge can drain to 0v in order to turn the MOSFET off.