Yes, so long as it does not require its own action
Using emerald razor is a standard action; you cannot apply its benefit to any other type of action, or to another standard action. So no emerald razor on a charge or whatever.
But it is still a weapon attack, and everything that would benefit just any weapon attack applies to it. That includes both Power Attack and Weapon Focus. The attack you make with emerald razor is exactly like any other attack you would have made, except it target’s touch AC instead of regular AC. Everything else is the same.
For the record, it’s far from the only way to achieve this. The core brilliant energy weapon property does this for all your attacks, though it does have a large drawback in its inability to attack constructs or undead. The wraithstrike spell from Spell Compendium allows the caster to target touch AC with all attacks for one round, as a swift action. The Deep Impact feat from Expanded Psionics Handbook allows you to treat any attack (including that as part of a charge, full-attack, or some other maneuver) as a touch attack if you expend Psionic Focus.