We don't really need to know how it works, only that it does work. Which hasn't been proven yet either, AFAIK.
Maybe he's accidentally found a loophole in the laws of physics.
It is also quite likely that even if this reaction does produce a net energy gain, the gain will be too small to function as a practical source of energy.
False assumption. He is not 'creating' energy - he is using a fuel (Nickel and Hydrogen). Just like your car, you drop a substancial amount of power out of your battery to start the engine, the engine starts burning gasoline mixed with air - and you get substancially more power out of your car's engine than your battery put in, and continues to pour in. Try disconnecting your battery on your gas engine - and the engine will stall. Does this mean you are creating energy? Or somehow 'creating' energy? No.
This process takes 400 Watts to sustain - and delivers in excess of 10,000 Watts by catelizing Nickel and Hydrogen into Copper.