Impulse response to a volatility shock

Unfortunately, this is a common issue. At the current stage, you can either use the Andreasen et al. codes or use IRFs as deviations from the ergodic mean in the absence of shocks (EMAS) as in Fernandez-Villaverde et al (2011), Born/Pfeifer (2014).
See the discussion in [Jumping IRFs to second-order shock to TFP)