The invention provides an emission control system for treatment of an exhaust gas stream that includes an oxidation catalyst composition disposed on a substrate in fluid communication with the exhaust gas stream; at least one selective catalytic reduction (SCR) composition disposed on a substrate downstream from the oxidation catalyst composition, and a hydrogen injection article configured to introduce hydrogen into the exhaust gas stream upstream of the oxidation catalyst composition or downstream of the oxidation catalyst composition and upstream of the at least one SCR composition. The invention also provides a method of treating an exhaust gas stream, the method including receiving the exhaust gas stream into the emission control system of the invention and intermittently introducing hydrogen upstream of the oxidation catalyst article or downstream of the oxidation catalyst article and upstream stream of the SCR article.