Clean Hydrogen from Aqueous Water−Gas Shift\nReaction at Near-Ambient Temperature

Clean hydrogen generation from water\nusing CO as the reducing agent\nis demonstrated in an aqueous water–gas shift reaction (AWGS)\nunder ambient conditions. The aqueous phase water–gas shift\nreaction proceeds at 40 °C and 3 atm, with formic acid as the\nintermediate. Formic acid produced by a CO hydration reaction is subsequently\ndehydrogenated to yield H<sub>2</sub> and CO<sub>2</sub>. The CO hydration\nstep with a small positive Δ<i>G</i>° is enabled\nby elevating the CO partial pressure and using an aqueous [RuEDTA(CO)]<sup>−</sup> catalyst prepared by dissolving the precursor [RuHEDTA(Cl)]K·2H<sub>2</sub>O. The complex ion [RuEDTA(CO)]<sup>−</sup> is denoted\nas the hydration catalyst (hyCat). Formic acid dehydrogenation is\ncarried out over the heterogeneous catalyst PtRuBiO<sub><i>x</i></sub> confined in a dehydrogenation reaction chamber. The use of\na two-chamber reactor for the AWGS reaction provides isolation of\nthe product hydrogen from the gas reactants, thus conveniently producing\nhydrogen with little or no CO. Using the two-chamber AWGS reactor,\nrates are measured at CO partial pressures of 3–11 atm and\ndifferent [RuHEDTA(Cl)]K·2H<sub>2</sub>O concentrations up to\n5 mM. A model combining liquid-film transport and enzyme kinetics\nis proposed for the two-step AWGS reaction to fit the available data.