Systems and methods for operating passive nitrogen oxide adsorbers in exhaust aftertreatment systems

A method comprising:

• while exhaust gas is received by a passive NOx adsorber (PNA), detecting a torque demand of an engine that is greater than a threshold value;
• responsive to detecting that the torque demand is greater than the threshold value, engaging a motor coupled to a battery system with a drive shaft to meet at least a portion of the torque demand;
• and
• in response to the engagement of the motor with the drive shaft resulting in less than the torque demand being met, engaging the engine with the drive shaft to meet at least a portion of a remainder of the torque demand.

A system comprising:

• a controller configured to:
• determine that an effectiveness of a catalyst in reducing NOx is below a threshold level;
• in response to determining that the effectiveness of the catalyst in reducing NOx is below the threshold level, control a valve to direct exhaust gas to a passive NOx adsorber (PNA);
• subsequent to controlling the valve to direct exhaust gas to the PNA, determine that the effectiveness of the catalyst is no longer below the threshold level;
• and
• in response to determining that the effectiveness of the catalyst is no longer below the threshold level, continue to control the valve to direct exhaust gas to the PNA for a predetermined duration and increase a load on the engine by mechanically engaging a generator with the engine, and utilize resulting electrical energy generated by the generator to charge a battery system.