PSA Citroën patent number FR2880657 entitled "Circuit exhaust gas recirculation" (with reformer and hydrogen injection to cause combustion)
(...) It has been shown that addition of hydrogen-rich gas (H2) in the intake manifold of the combustion chamber during an exhaust gas recirculation, reduces emissions hydrocarburres unburned (HC), carbon monoxide (CO) and soot.
The engine power output is improved while limiting emissions of carbon products.
Of manner known per se, the fuel reforming is obtained by reacting fuel molecules with water and / or air to produce hydrogen according to the following chemical reactions ...
Following in the document.
Read more and debate: injection of hydrogen into the fuel