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.


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