An internal combustion engine system includes an internal combustion engine, an exhaust aftertreatment system with a catalytic converter configured to receive exhaust gas from the internal combustion engine, and a light-off catalyst system including an electrolyzer configured to perform an electrolysis of water to produce a mixture of hydrogen and oxygen gases. A conduit is in fluid communication between the electrolyzer and an intake of the internal combustion engine. A controller is configured to supply the mixture of hydrogen and oxygen gases to the engine intake during a cold start to facilitate rapidly warming the catalytic converter to a light-off temperature.
