I will provide some useful information to help you figure out how to get money back from a divorce attorney:
The first thing to do is to set up a meeting with your attorney to explain your concerns about the bill. See if you can come to a meeting of the minds about what you should have been charged versus what you have been charged.
Your lawyer should provide you a bill which gives you a sense of what he did for your money. However, you need to understand, there often isn't "tangible output". Tangible output is not something against which you can judge a fair legal bill. A lot of our time is simply spent talking to people. That isn't tangible output, but it is something for which you will be billed. Nor are you required to give permission for everything the lawyer does. If your lawyer contacted you to ask you if he could do something, he would charge you for each of those contacts, figure 6 minutes to send an email 6 minutes to read the email with your permission to go forward. That would add up fast. (Or 10 or 15 minutes, depending on how he charges.)
Lawyers simply do not stop and contact their clients for permission to act once they have been retained. They go forward with the representation as they believe is appropriate. For example, your lawyer is not going to ask your permission to speak with opposing counsel or write a letter or conduct research on a legal issue. He is going to call you when you need to be updated or asked a question or if he needs something from you. If he has begun negotiations and wants to know if you agree to the settlement, he will call you there too. He should also call you if he has given you an estimate and the cost is going to go well beyond the expected.
Family law cases are expensive. If the opposing side is not cooperative, they get even more expensive. If the client calls or emails a lot, that makes them more expensive too.
If you are unable to come to an agreement, then your next step is to look and see if you have access to a fee dispute process handled by a local bar association. You can find more information here. Resolving Fee Disagreements
A fee dispute, incidentally, is not something over which to file an ethics complaint, unless the fee itself shows unethical conduct. A dispute about a fee, generally speaking, has nothing to do with the ethical rules.
Remember, unless the lawyer's fee is essentially outrageous for what he is claiming he did, then you will are unlikely to be successful in a fee dispute. So your best bet is simply to work through the issue with your lawyer and resolve it.
Additionally, In order to answer your question appropriately, I would need to know what you expected from your divorce lawyer. Your question states that you where charged for "work for which no tangible output exists"; in your mind, what is tangible output from a divorce proceeding? What was tangible in your marriage? If you mean that the pieces of paper declaring your dissolution of marriage or your marriage are the tangible items that you should pay for, then I would suggest that your understanding of the effort that went into the production of those pieces of paper is profoundly lacking (and may very well explain why you had a divorce attorney to begin with). Even "uncontested" divorces (with very, very rare exceptions) have some element which is contested and requires some negotiation. Do you consider the time your lawyer spent conducting that negotiation to be of no value because you can't touch it?
Of course if you mean that your lawyer billed you for time that was not expended or for activities that did not further your divorce proceeding, then you can, after giving the lawyer an opportunity to explain themselves, file a grievance against the attorney with the bar disciplinary office or committee in your jurisdiction. In many jurisdictions you can find out how and where to file your grievance at your local courthouse (and many jurisdictions have this information online). Most bar disciplinary bodies have a mechanism to order (with the aid of the court if need be) return of unearned funds.
As far as the second prong of your question regarding work you "never authorized them to do", you need to clarify what work you're talking about. I am assuming you were given and directed to read, understand and sign a retainer agreement outlining the terms of your lawyer's representation of you (if not, that alone s a grievable offense in most jurisdictions). So, for instance, if you where billed for time "reviewing bank statements", dd you expect your lawyer to contact you before he/she reviewed the records to see if you "authorized" it? or to call you before they prepared a subpoena to obtain those records? If you did expect that kind of minucial micro-management of your divorce proceeding, then either your lawyer failed to adequately apprise you of how their representation works, or you have completely unreasonable expectations, or you're just trying to beat paying your bill.