The chemical reaction provides carbon dioxide and water, and since CO2 is a known greenhouse gas, this kind of alternative would be better than usual ones based on oil, but still not a solution. While the reaction product is more CO2, one of the main worries of today in terms of ocean acidification and atmospheric unbalance, the issues will continue and also in terms of air toxicity and quality of life.
Sadly some companies try to advertise even oil engines as ecologic cars, drawing green leaves and other stereotypes. Although respecting the truth, there's no vehicle with an exhaust tube being ecologic. If the car is ecologic, why don't manufacturers put the exhaust tube inside the space for driver and passengers? With closed windows, they will have the problems of "ecologic" cars as the environment —our only home by the way— does today.
The most important element to consider is the number of vehicles that right now are being utilized, so any technology that implies pollution must be out of the list or the development will continue in lamentable degrees of precarious sustainability and creating a deeper problem for humanity.