The decomposition of formic acid/formate in the presence of homogeneous metal catalysts is studied to produce hydrogen. [Cp*Rh(bpy)(H2O)]2+ has been often used as an electrochemical and photochemical catalyst due to the relatively high efficiency and selectivity to regenerate NADH. Chemical regeneration of NADH is performed using [Cp*Rh(bpy)(H2O)]2+ and sodium formate as a reducing agent. As a proposed reaction mechanism, a [Cp*Rh(bpy)(H2O)]2+-formate intermediate released carbon dioxide to form a hydridorhodium(III) intermediate which consecutively reduces NAD+ to produce 1,4-NADH. Reduced graphene oxide (rGO), which is highly dispersed in water due to its hydrophilic oxygen functional groups and has electric properties superior to those of graphene oxide (GO), is intensively utilized to prepare efficient systems for optical sensors, catalysts, light antennas, and other applications. The photoexcited electrons of most chromophores are rapidly transferred to rGO when they are in close contact. rGO attached with organic chromophores was recently used to collect wide-range visible light energy for a photoregeneration system of 1,4-dihydronicotinamide adenine dinucleotide (NADH) with a molecular Rh catalyst, but direct interaction between rGO and Rh catalyst was not investigated. A cyclopentadienyl rhodium catalyst derivatized with pyrene was used to study the effects of a reduced graphene oxide (rGO) on visible light driven photocatalytic hydrogen production using formate and Pt nanoparticles. The pyrene-derivatized rhodium catalyst was immobilized on rGO by p-p stacking interactions. A tight formation of the Rh catalyst on rGO surprisingly enhanced the hydrogen production upon visible light irradiation, in contrast with the results using a thin formation of the catalyst or the unfunctionalized Rh catalyst. Our results also demonstrated that the catalytic stability of the pyrene-functionalized Rh complex dramatically increased when it was immobilized to rGO during the photocatalytic reaction cycle. RGO played a crucial role in efficiently transferring electrons from the Rh(III)-hydrides to the platinum nanoparticles.

Visible-light-driven hydrogen photoproduction with Rh(III) catalysts and platinum nanoparticles loaded on graphene oxides

251st National Meeting (2016)

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