What is a sacrificial agent? I came across this reading a journal article. Here I have the context:


  Here we report for the first time the synthesis of $\ce{TiO2}$ NPs
  on a layered $\ce{MoS2}$/graphene (MG) hybrid for use in
  photocatalytic H2 production. It is shown that the activity of
  the $\ce{TiO2}$ NPs is significantly enhanced by the presence of this
  layered MG cocatalyst. In this case, ethanol was used as a
  sacrificial agent, as it is a sustainable and renewable source and
  showed very good performance with this photocatalyst;
  however, other sacrificial agents (e.g., glycerol) can be used
  to make this strategy feasible.


Google results came up with similar instances.

My guess is that it would be a chemical consumed in a reaction, but one that doesn't contribute to the structure of the product. Thoughts?
"Sacrificial agent" usually refers to something variable, but with little value, that can be used to produce something specific or carry out a specific function. In this case, an alcohol (ethanol or glycerol) is sacrificed to act as a source of hydrogen gas, while the titanium species is a catalyst that is activated by light to allow generation of hydrogen.