( ( A ( hydrogen ( fuel cell ) ) ) ( ( is ( ( an ( electrochemical cell ) ) ( that ( uses ( ( the ( a ( spontaneous ( redox reaction ) ) ) ) ( to ( produce ( current ( that ( can ( do work ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT A) (NN hydrogen) (NN fuel) (NN cell)) (VP (VBZ is) (NP (NP (DT an) (JJ electrochemical) (NN cell)) (SBAR (WHNP (WDT that)) (S (VP (VBZ uses) (S (NP (DT the) (DT a) (JJ spontaneous) (NN redox) (NN reaction)) (VP (TO to) (VP (VB produce) (NP (NP (JJ current)) (SBAR (WHNP (WDT that)) (S (VP (MD can) (VP (VB do) (NP (NN work))))))))))))))) (. .)))
A hydrogen fuel cell is an electrochemical cell that uses the a spontaneous redox reaction to produce current that can do work.
(ROOT (S (NP (DT A) (JJ voltaic) (NN cell)) (VP (VBZ generates) (NP (DT an) (JJ electric) (NN current)) (PP (IN through) (NP (NP (DT a) (NN reaction)) (VP (VBN known) (PP (IN as) (NP (DT a) (PRN (-LRB- -LRB-) (NP (NN n)) (-RRB- -RRB-)) (JJ spontaneous) (NN redox))))))) (. .)))