The Favonius lance, hands down, is the best weapon for supporting characters that use polearms. You can funnel energy particles to your main DPS or consume them to recharge your elemental burst. I've got two refined copies of the Favonius lance to use on Xiangling and Shenhe. Though I usually switch between the Calamity Queller and the Favonius lance, it's better to have flexibility.