For increase the voltage more than 5V you need a booster or something ....
I have attach a photo from a schematic that i have made some years back it was to drive a dimer for lights and use 0-10v to control it, you must play with the pwm commands to go from 0 to 5 volt in arduino side and at the output you will have double value .
Another one site (i quick check on google) is arduino 0-10v ? - DIY Projects - Nano-Reef Community
and this Arduino Playground - RegulatedPositiveVoltageBooster
PS Read the questions from the members they ask here and answer it, it is not nice to ignore it they will not happy to help again and i found logical ....
Good luck.
