Shares of hydrogen fuel cell (HFC) specialist Plug Power (NASDAQ:PLUG) popped higher on Tuesday before dipping slightly following a key hiring announcement. The company announced that Dean Fullerton will step in as the new Chief Operating Officer. Previously, Fullerton worked at Amazon (NASDAQ:AMZN), where he led engineering services for North America, Europe and emerging markets. Though the announcement drew positive attention to PLUG stock, the underlying business environment remains challenging.According ...