Have you understood the roles & responsibilities of IT PROFESSIONALS with regards of their JD and previous experience? If yes, then you can define your own questions to test relevant functional competencies as technical competencies are tested by technical team.
Also, take support of senior HR professionals in your organisation, if there are any.
just because you are HR, please do not ask IRRELEVANT QUESTIONS so called STUPID QUESTIONS as many HR are fond of asking such questions. By the end of the interview, please leave any scope for interviewee to give a bad remark about HR.
With profound regards