All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
There is not doubt that this is an excellent idea, through which you may receive considerable reward if you follow Sharee’ah instructions. It is a kind of Da’wah for Allaah and for Islam and it is a kind of Jihaad in the cause of Allaah. The Prophet, sallallaahu ‘alayhi wa sallam, was reported to have said that anyone who calls others to do a good deed will receive a reward equal to that of those who follow him, without diminishing their reward. [Muslim]
However, you must obtain prior permission from your employer for doing this. Unless you have permission, you are not permitted to use their material and your work time, which is exclusively for them, to do this. This good End – Da’wah - does not permit using prohibited means or as the saying goes: 'Ends don't justify means'.