Shares of Plug Power Inc dipped 5.6% on Friday, closing at $2.19, pressured by a TD Cowen downgrade that nudged the hydrogen fuel-cell company back toward the $2 mark. The stock fluctuated between $2.14 and $2.33 during the session, after ending Thursday at $2.32. Volume hit around 114 million shares, surpassing the company’s recent averages. Meanwhile, the Nasdaq Composite climbed 0.81%, and rival Ballard Power Systems gained 1.1%.