Perhaps a connection to LENR experiments would be more obvious if somehow this persistent intense heating effect at the cathode as shown above could be integrated in a small sealed cell containing hydrogen. Putting aside any unusual/anomalous hydrogen interaction that could ensue, the reducing environment would make the heating easier to observe, and a low pressure would help increasing temperatures, in addition of allowing a larger electrode gap to be used. I can't help but feel that I might be reinventing the wheel/[incandescent lamp], though.
In the example above the glowing sphere must have had a temperature > 1500 °C, by the way.
The moment you brought up silver (Ag) I thought of the hydrated silver pellet based experiments done by Mills and Co. Maybe encapsulating water in the molten metal and shocking it from a safe distance would be interesting if not possibly explosive.