If you are initiating the divorce, then you must pay the mahr to your wife before the divorce if you have not already done so.
Other than that, there is no obligation on you, however, it is better to give more than just the mahr as the Quran states:
Divorce is twice. Then, either keep [her] in an acceptable manner or release [her] with good treatment. And it is not lawful for you to take anything of what you have given them unless both fear that they will not be able to keep [within] the limits of Allah . But if you fear that they will not keep [within] the limits of Allah, then there is no blame upon either of them concerning that by which she ransoms herself. These are the limits of Allah, so do not transgress them. And whoever transgresses the limits of Allah – it is those who are the wrongdoers.