"Hydrogen peroxide is water (H2O) with an extra oxygen molecule (H2O2)."
https://health.clevelandclinic.org/what-is-hydrogen-peroxide-good-for/
"it injects the hydrogen directly into the car’s air intake manifold (similar to nitrous oxide injection) to be combusted in the engine’s cylinders"
https://www.bmw-tech.org/wiki/BMW_Hydrogen_7
"Hydrogen peroxide is H2O2; water is H2O. It isn't the hydrogen that is easily stripped from the molecule, but the oxygen. Hydrogen peroxide is a powerful oxidizing agent."
"Introducing it into the combustion chamber along with the fuel should enhance combustion. This would increase the power produced by the engine, because more of the fuel would be burned in the combustion chamber."
"In short, injecting h2O2 would be expected to act much like denser air, with more mass of O2 -- and the closed loop nature of the injection system will compensate to keep emissions within range."
"The one factor that the original question ignored is the concentration of hydrogen peroxide to be used. One would likely "assume" the hydrogen peroxide of use would be the OTC 3 % water solution. Industrial H2O2 is typically 30 % aqueous solution, and that starts to become hazzardous."
"In this case you are spraying water particles into the intake system that remain as small droplets that do not compress. Hydrogen peroxide used as rocket fuel is highly explosive. 3% isn't very promising as a performance increaser. The 97% of water isn't going to burn."
"H2O2 is supposed to be injected as a vapor into th eincoming air stream"
https://cr4.globalspec.com/thread/21702/Hydrogen-Peroxide-Injection-Systems-for-Engines
"Arguably the coolest part of the BMW M4 GTS is its water-injection system, a production-car rarity. It was a big part of how BMW was able to turn up the standard M4's 3.0-liter twin-turbo inline-six from 425 hp to 493 for the GTS. So how can a tank of distilled water create such a substantial boost in power?"
https://www.roadandtrack.com/new-cars/car-technology/a25833896/how-water-injection-increases-horsepower/