I'd suggest waking up earlier and feeding first, then walking before you leave for work. I get up, let the dog out to pee, feed him around 6:30, shower, have my own breakfast, catch up on the internet

, go for a walk around 7:30, and leave for work around 8am. When I get home from work, I let him out, then feed him, cook & eat my own dinner, then walk him about an hour later.
He's a small dog, so a half-hour walk will tire him out. A larger, more energetic dog will need more exercise.
The idea is that dogs typically need to relieve themselves about an hour after eating. You also don't want to exercise a dog on a full stomach, and likewise don't want to feed right after exercising.