Hi , I just did this with my boy Oscar..
He is 1yr 8 months up until just about 3 weeks ago he was 100% litterbox trained. One day I decided I wanted to have him 100 % outside trained.
I too am home all day so I thought i would try it..
I took up his litterbox and all the pads completely..
Started taking him out first thing in the morning,, every 30 minutes , i use the words " go potty " for pee pee & " go poopy " for well poopy. But you use whatever words would work for you.
I take him out after each meal , after naps , after big drinks ..
I gradually lengthened the out time from every 30 minutes to every hour..
Within a matter of days , Oscar was 100 % outside potty trained..
I was so amazed and proud at how quickly he took to it..
When we go out to do groceries (usually 2 to 3 hours) Oscar holds it the whole time we are gone.. I take him out immediately upon getting home and he does his potty..
Of course your pup is much younger than Oscar so it may take a bit more time but trust me he can do it..