In Situ Determination of Photobioproduction of H2 by In2S3-[NiFeSe] Hydrogenase from Desulfovibrio vulgaris Hildenborough Using Only Visible Light

An interesting strategy for photocatalytic production of hydrogen from water and sunlight is the formation of a hybrid photocatalyst that combines an inorganic semiconductor able to absorb in the visible light spectral range with an enzymatic catalyst for reducing protons. In this work we study how to optimize the interfacing of In2S3 particles with the soluble form of [NiFeSe] hydrogenase from Desulfovibrio vulgaris Hildenborough by means of its initial H2 photoproduction rate. The kinetics of the photocatalytic process was studied by membrane-inlet mass spectrometry, in order to optimize the interaction between both components of the hybrid photocatalyst. Membrane-inlet mass spectrometry allows measuring in the same experiment, for comparison, the rate of H2 production by the photocatalyst hybrid directly in the aqueous solution in real time and the result of a standard assay of the hydrogenase activity. An incubation period of 6 h with mild stirring of hydrogenase with In2S3 particles was necessary for optimal interaction of the enzyme molecules with the porous surface of the semiconductor. A turnover frequency of the NiFeSe hydrogenase (TOFHase) for H2 photobioproduction of 986 s–1 was measured under the optimized conditions. This means that the immobilized hydrogenase has a photocatalytic efficiency for H2 generation which is 94% of that obtained in the standard specific activity test of H2 production using reduced methyl viologen as an electron donor.This work was funded by the Spanish MINECO (projects CTQ2015-71290-R and ENE2013-46624-C4-1-R) and by Fundação para a Ciência e a Tecnologia (Portugal) (Grants UID/Multi/04551/2013 and PTDC/BBB-BEP/2885/2014 and Ph.D. fellowship SFRH/BPD/xxx/201x). C.T. thanks the Spanish MINECO for her BES-2013-064099 contract.Peer reviewe