A rapid start reactor is provided that can be used, for example, in a water gas shift reactor of a fuel processor. A reactor has a catalyst support structure with one or more surfaces overlaid with an active coating that includes a catalyst. The active coating heats upon exposure to a non-thermal energy source. The reactor also includes a generator of non-thermal energy for applying non-thermal energy to the active coating. Methods for operating such a reactor during transient and/or start-up conditions are also provided.