( ( As ( I ( understand it ) ) ) ( , ( ( fuel cells ) ( ( work ( by ( ( recombining ( ( hydrogen and ) oxygen ) ) ( ( ( using ( ( some sort ) ( of ( a catalyst ) ) ) ) or ) ( membrane ( to ( ( ( separate ( the ( redox reaction ) ) ) and ) ( generate ( a current ) ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN As) (S (NP (PRP I)) (VP (VBP understand) (NP (PRP it))))) (, ,) (NP (NN fuel) (NNS cells)) (VP (VBP work) (PP (IN by) (S (VP (VBG recombining) (NP (NN hydrogen) (CC and) (NN oxygen)) (S (VP (VP (VBG using) (NP (NP (DT some) (NN sort)) (PP (IN of) (NP (DT a) (NN catalyst))))) (CC or) (VP (VBG membrane) (S (VP (TO to) (VP (VP (VB separate) (NP (DT the) (NN redox) (NN reaction))) (CC and) (VP (VB generate) (NP (DT a) (JJ current))))))))))))) (. .)))
As I understand it, fuel cells work by recombining hydrogen and oxygen using some sort of a catalyst or membrane to separate the redox reaction and generate a current.
(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))))))) (. .)))