Can a power of attorney borrow off a certificate of deposit if the grantor is not deceased?

The attorney-in-fact under a Power of Attorney cannot do any self-dealing whatsoever. What you suggest would be illegal. If you need a loan from the principal it should be in writing with an unrelated witness and notary signing the promissory note. In that transaction you could not sign for the principal. Your actions as a fiduciary are governed by law. You need to make certain not to act in such a way as to make yourself vulnerable to legal challenges later or accusations of self dealing.