# 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?