The Siphon Grenade was designed to work with the Doom Marine's Praetor suit - specifically to make use of the Argent receptors found in the gloves and chest plates.
The grenade has 3 stages. When primed, the grenade releases a positively charged particle field around itself and the operator's hand. Then, when the grenade is released and explodes it releases a negatively charged particle field, over a distance of a few meters. The negatively charged particles attract Argent plasma from any demon caught in the radius, tearing the plasma from their cells. Finally, the positively charged Praetor suit then attracts the negatively charged Argent cloud, and gathers the plasma. This siphons energy back into the suit, partially healing the Doom Marine.