Volcanoes and the Habitable Zone

I was reading space.com earlier and saw an article about how volcanoes can impact exoplanet atmosphere and climate. While I suppose most are familiar with the impacts volcanic eruptions can have here on earth (if you're not, check out 1816, the Year Without a Summer, for an example), what the article is discussing is somewhat different. Instead of dust clouds it is concerned with hydrogen released by substantial volcanic eruptions producing an atmosphere that allows a planet to retain water across a larger distance from its star. Essentially, enough hydrogen in the atmosphere expands the habitable zone outwards. The article discusses some possibilities with respect to the recently-discovered TRAPPIST-1 system, which discovery I mentioned in an earlier blog post. Very interesting stuff.