A biomimetic self-assembled cobaloxime@CdS/rGO hybrid for boosting photocatalytic H2 production.

A biomimetic CoPe@CdS/rGO hybrid that self-assembles via the integration of a molecular cobalt catalyst and CdS nano-semiconductor on reduced graphene oxide was constructed for boosting photocatalytic H2 production. Photoinduced electron transfer from CdS/rGO to the molecular catalyst occurs and a long-lived charge-separation state forms for high H2 production.

Highly Efficient Photocatalytic Conversion of CO2 to CO Catalyzed by Surface-Ligand-Removed and Cd-Rich CdSe Quantum Dots.

Surface ligand-removed and Cd-rich CdSe quantum dots (QDs) exhibited exceptional activity as photocatalyst for the conversion of CO2 to CO. A CO production rate up to 789 mmol g-1 h-1 was achieved in a triethylamine/dimethylformamide mixture under visible-light irradiation. Mechanistic studies revealed that improving the Cd/Se stoichiometric ratio and exposing more active surface Cd atoms significantly enhanced the activity of CdSe QDs for CO2 photoreduction.

Photocatalytic reduction of CO2 to CO and formate by a novel Co(ii) catalyst containing a cis-oxygen atom: photocatalysis and DFT calculations.

The conversion of carbon dioxide (CO2) to fuels or value-added chemicals by a photocatalytic system has recently been of growing research interest. One of the challenges is the development of new catalysts with high activity and low cost. Cobalt complexes have long been used as catalysts for the reduction of CO2 in either electrochemical or photochemical systems. Recently, a series of cis-CoII complexes of tetradentate pyridine-amine ligands (N4-ligands) exhibited high activity in the reduction of CO2 in homogeneous photocatalytic systems. However, only CO was obtained as the reduction product. In this regard, herein, we report a novel cis-CoII complex C1 supported by an N4 ligand derivatized with TPA (TPA = tris(2-pyridylmethyl)amine). In contrast to the aforementioned CoII catalysts, which contain two halogen atoms at cis-positions, C1 contains one oxygen atom at one cis-coordination site. The structure of C1 was fully characterized by MS, elemental analysis, and single-crystal X-ray diffraction. Experiments on the photocatalytic reduction of CO2 revealed that C1 is able to convert CO2 to not only CO but also formate in a homogeneous system containing C1 as a catalyst, Ir(ppy)3 as a photosensitizer, and triethylamine as an electron donor under visible-light irradiation. The catalytic activity and distribution of reduction products of this system are highly affected by the solvent environment. The presence of water in this system enhances the efficiency of 2H+-to-H2 and CO2-to-formate conversions. Electrochemical and steady-state emission quenching experiments indicate that photoinduced electron transfer from excited Ir(ppy)3 to C1 is thermodynamically feasible. A photogenerated CoI species is suggested to be the active species involved in the reduction of CO2 and protons. DFT calculations were performed to elucidate the catalytic pathways of the formation of CO, formate, and H2 in this system; four pathways, namely, one for the formation of CO, one for the formation of hydrogen, and two for the formation of formate, were suggested. The results revealed that the oxygen atom at the cis-coordination site in C1 plays an important role in stabilizing the transition state during the transformation of CO2 at the cobalt center.