Photocatalysts For CO Research Articles

Ir(tpy)(bpy)Cl] as a Photocatalyst for CO2 Reduction under Visible‐Light Irradiation

AbstractMononuclear iridium(III) terpyridine (tpy) 2,2′‐bipyridine (bpy) [Ir(tpy)(bpy)Cl]2+ photocatalysts (denoted [Ir(bpy)]) were developed for selective CO2 reduction to HCOOH under visible light. The CO2 reduction product could be changed dramatically by substituting a 2‐phenylpyridine (ppy) ligand with bpy, with the mononuclear Ir ppy complex ([Ir(tpy)(ppy)Cl]+) acting as a photocatalyst for selective CO2 reduction to CO. A mechanistic study showed a structural change in [Ir(bpy)] during the photocatalytic reaction. The [Ir(bpy)] complex was transformed into an iridium–hydride complex ([Ir(tpy)(bpy)H]2+) during an early stage of the photocatalytic reaction. However, [Ir(tpy)(bpy)H]2+ did not function as a key intermediate in the photochemical CO2 reduction because an additional structural change occurred. The tpy ligand of the Ir complex was reduced to piperidine‐2,6‐di‐2‐pyridine ligand during the photocatalytic reaction, resulting in the production of [Ir(piperidine‐2,6‐di‐2‐pyridine)(bpy)H]2+, which was the actual photocatalyst for HCOOH production.

Synthesis of N-doped graphene-functionalized Zn1.231Ge0.689N1.218O0.782solid solution as a photocatalyst for CO2reduction and oxidation of benzyl alcohol under visible-light irradiation

N-Graphene/ZnGeON hybrids were assembled through electrostatic adsorption of positively-charged Zn2GeO4nanorods with negatively-charged graphene oxide (GO) and calcinated by a high temperaturein situnitridation technique under NH3flow.

Ruthenium-cobalt dinuclear complexes as photocatalysts for CO2 reduction.

A series of Ru-Co dinuclear complexes have been synthesized and assayed as photocatalysts for the reduction of CO2 to CO in organic solvents. The Ru-Co complexes, with tris-diimine coordination at the Co ion, are the best supramolecular photocatalysts for CO2 reduction with a non-noble metal catalytic center reported so far.

Ti2CO2MXene: a highly active and selective photocatalyst for CO2reduction

We investigated the reduction of CO2at the oxygen vacancy on MXene monolayers and Ti2CO2exhibited the best catalytic performance. Moreover, we proposed that CO and H2can introduce sufficient oxygen vacancies on O-terminated MXene.

Highly Active NaTaO3 -Based Photocatalysts for CO2 Reduction to Form CO Using Water as the Electron Donor.

Doped NaTaO3 (NaTaO3 :A, where A=Mg, Ca, Sr, Ba, or La) has arisen as a highly active photocatalyst for CO2 reduction to simultaneously form CO, H2 , and O2 using water as the electron donor when used with an Ag cocatalyst, under UV irradiation, and with 1 atm (0.1 MPa) of CO2 . The ratio of the number of reacted electrons/holes was almost unity, indicating that water was consumed as the electron donor. A liquid-phase reduction method for loading of the Ag cocatalyst was superior to photodeposition and impregnation methods. The Ag cocatalyst-loaded NaTaO3 :Ba was the most active photocatalyst in water with no required additives. The addition of bases, such as hydrogencarbonate, was effective to enhance the CO formation for Mg-, Ca-, Sr-, Ba-, and La-doped NaTaO3 photocatalysts with an Ag cocatalyst. Ca- and Sr-doped NaTaO3 photocatalysts showed especially high activity along with the Ba-doped photocatalyst in the aqueous NaHCO3 solution. The selectivity for the CO formation [CO/(CO+H2 )] on Ca-, Sr-, and Ba-doped NaTaO3 photocatalysts with Ag cocatalyst reached around 90 %.

TiO2 nanocontainers and nanospheres as photocatalysts for CO2 reduction and photoelectrochemical water splitting: structural modification

TiO₂ nanocontainers and nanospheres as photocatalysts for CO₂ reduction and photoelectrochemical water splitting: structural modification

Photocatalyses of Ru(II)–Re(I) binuclear complexes connected through two ethylene chains for CO2 reduction

We synthesized two novel supramolecular photocatalysts for CO2 reduction [Ru(BL1)Re(CO)3Cl]2+ (12+) and [Ru(BL1)Re(CO)2{P(p-F-C6H4)3}2]3+ (33+), where BL1 is two 2,2′-bipyridine moieties connected through two ethylene chains. Compared to the corresponding supramolecular photocatalysts (22+, 43+) with only one ethylene chain in the bridging ligand (BL2), these complexes had stronger electronic interactions between the Ru and Re units through the two ethylene chains, which strengthened the oxidation power of the excited Ru unit. Although BL1 compounds functioned as photocatalysts for CO2 reduction by selectively providing CO, their photocatalyses were very different, especially, when compared with BL2 compounds. In the case of 12+, the quantum yield of CO formation (ΦCO) was larger than that of the corresponding BL2 compound. Conversely, ΦCO of the system using 33+ was approximately 40% less than the corresponding BL2 compound. The reasons for these differences were successfully clarified through mechanistic studies of these photocatalytic CO2 reductions.

Fabrication of Gold/Titania Photocatalyst for CO2 Reduction Based on Pyrolytic Conversion of the Metal–Organic Framework NH2-MIL-125(Ti) Loaded with Gold Nanoparticles

Titania exhibits unique photophysical and -chemical properties and can be used for potential applications in the field of photocatalysis. The control of TiO2 in terms of phase, shape, morphology, and especially nanoscale synthesis of TiO2 particles still remains a challenge. Ti-containing metal–organic frameworks (MOFs), such as MIL-125, can be used as sacrificial precursors to obtain TiO2 materials with diverse phase compositions, morphologies, sizes, and surface areas. MIL-125 is composed of Ti/O clusters as the secondary building units (SBUs) bridged by 1,4-benzenedicarboxylate (bdc). In this study, preformed and surfactant-stabilized gold nanoparticles (GNPs) were deposited onto the surface of amino functionalized NH2-MIL-125 during solvothermal synthesis. Targeted gold/titania nanocomposites, GNP/TiO2, were fabricated through the pyrolysis of GNP/NH2-MIL-125 nanocrystals. The modification of TiO2 with GNPs significantly increased the photocatalytic activity of the MOF derived TiO2 material for the re...

Construction of Interpenetrated Ruthenium Metal-Organic Frameworks as Stable Photocatalysts for CO2 Reduction.

Poor stability has long been a major obstacle to the practical applications of metal-organic framework (MOF) photocatalysts. This problem can be overcome by the use of structural interpenetration. In this work, by modifying Ru metalloligands, we have rationally designed two Ru-polypyridine based MOFs (with non-interpenetrated and interpenetrated structures, respectively), both of which exhibit similar photocatalytic activities for CO2 photoreduction. Remarkably, the interpenetrated Ru-MOF possesses good photocatalytic durability and recyclability, and shows much higher thermal and photic stability in comparison with its non-interpenetrated counterpart. To the best of our knowledge, this is the first time that the stability of MOF photocatalysts was improved by using structural interpenetration.

Efficient Photocatalysts for CO2 Reduction.

Three types of photocatalytic systems for CO2 reduction, which were recently developed in our group, are reviewed. First, two-component systems containing different rhenium(I) complexes having different roles; i.e., redox photosensitizer and catalyst in the reaction solution are described. The mixed system of a ring-shaped rhenium(I) trinuclear complex and fac-[Re(bpy)(CO)3(MeCN)](+) is currently the most efficient photocatalytic system for CO2 reduction (ΦCO = 0.82 at λex = 436 nm). The second is a series of supramolecular photocatalysts, which have units with different functions in one molecule, i.e., redox photosensitizer, catalyst, and bridging ligand. The highest durability and speed of photocatalysis were achieved by using this system (ΦCO = 0.45, TONCO = 3029, and TOFCO = 35.7 min(-1)). The third is a novel type of artificial Z-Scheme photocatalyst for CO2 reduction, of which photocatalysis is revealed by stepwise excitation of both a semiconductor photocatalyst unit and the supramolecular photocatalyst unit. This system has both strong oxidation and reduction powers.

Synthetic strategies to nanostructured photocatalysts for CO2reduction to solar fuels and chemicals

Advances in nanomaterials synthesis offer new routes to solar fuels and chemicals from CO2as a sustainable chemical feedstock.

Nitrogen-doped graphene-supported copper complex: a novel photocatalyst for CO2 reduction under visible light irradiation

Nitrogen-doped graphene immobilized with copper(ii) complex (GrN700–CuC) is demonstrated to be an efficient photocatalyst for CO2 reduction into methanol under visible light irradiation.

Role of quaternary N in N-doped graphene–Fe2O3 nanocomposites as efficient photocatalysts for CO2 reduction and acetaldehyde degradation

The quaternary N in N-doped graphene–Fe2O3 nanocomposites contributes to the obviously-improved photoactivities for CO2 reduction and for acetaldehyde degradation.

Gold-copper nanoalloys supported on TiO2 as photocatalysts for CO2 reduction by water.

Commercial P25 modified by Au-Cu alloy nanoparticles as thin film exhibits, for CO2 reduction by water under sun simulated light, a rate of methane production above 2000 μmol (g of photocatalyst)(-1) h(-1). Although evolution of hydrogen is observed and O2 and ethane detected, the selectivity of conduction band electrons for methane formation is almost complete, about 97%. This photocatalytic behavior is completely different from that measured for Au/P25 (hydrogen evolution) and Cu/P25 (lower activity, but similar methane selectivity). Characterization by TEM, XPS, and UV-vis spectroscopy shows that Au and Cu are alloyed in the nanoparticles. FT-IR spectroscopy and chemical analysis have allowed one to detect on the photocatalyst surface the presence of CO2(•-), Cu-CO, and elemental C. Accordingly, a mechanism in which the role of Au is to respond under visible light and Cu binds to CO and directs the reduction pathway is proposed.

Graphene oxide as a promising photocatalyst for CO2to methanol conversion

Photocatalytic conversion of carbon dioxide (CO(2)) to hydrocarbons such as methanol makes possible simultaneous solar energy harvesting and CO(2) reduction, two birds with one stone for the energy and environmental issues. This work describes a high photocatalytic conversion of CO(2) to methanol using graphene oxides (GOs) as a promising photocatalyst. The modified Hummer's method has been applied to synthesize the GO based photocatalyst for the enhanced catalytic activity. The photocatalytic CO(2) to methanol conversion rate on modified graphene oxide (GO-3) is 0.172 μmol g cat(-1) h(-1) under visible light, which is six-fold higher than the pure TiO(2).

A new class of highly solvatochromic dicyano rhenate(i) diimine complexes – synthesis, photophysics and photocatalysis

A new class of dicarbonyl dicyano rhenate(I) diimine complexes, cis,trans-[Re(CO)(2)(CN)(2)(N-N)](-), with highly environmentally sensitive MLCT absorption and emission properties was synthesised and characterised. Preliminary experiments revealed that these complexes are active photocatalysts for CO(2) reduction.

A Highly Efficient Mononuclear Iridium Complex Photocatalyst for CO2 Reduction under Visible Light

A Highly Efficient Mononuclear Iridium Complex Photocatalyst for CO₂ Reduction under Visible Light

A Highly Efficient Mononuclear Iridium Complex Photocatalyst for CO2 Reduction under Visible Light

A Highly Efficient Mononuclear Iridium Complex Photocatalyst for CO₂ Reduction under Visible Light

Two bifunctional Ru II/Re I photocatalysts for CO 2 reduction: A spectroscopic, photocatalytic, and computational study

Two Ru II/Re I dimers, [Ru(dmb) 2( L1)Re(CO) 3Cl] ( 1) and [Ru(dmb) 2( L2)Re(CO) 3Cl] ( 2), were synthesized and characterized, and their electrochemical and spectroscopic properties together with their photocatalytic CO 2 reduction activities were evaluated (dmb = 4,4′-dimethyl-2,2′-bipyridine; L1 = 1,2-bis(4′-methyl-2,2′-bipyridyl-4-yl)ethane; L2 = 1,2-bis(4′-methyl-2,2′-bipyridyl-4-yl)ethene). The structures of 1 and 2 are identical except for the difference in the conjugation content of bridging ligands (–CH 2–CH 2– for 1 and –CH CH– for 2). Density functional theory (DFT) methods were employed to model the ground-state electronic transition and electrochemical properties of both catalysts. Electronic transitions were identified using UV–Vis spectroscopic techniques, aided by time-dependent density functional theory (TD-DFT) methods. The redox properties of two complexes under N 2 and CO 2 pressure have been studied by means of cyclic voltammetric measurements. When the cyclic voltammetry was performed in the presence of CO 2, a substantial current enhancement was observed for the reduction wave of 1 and 2. Additionally, significant higher turnover numbers of CO formation in the photocatalytic CO 2 reduction are observed for 1 than that for 2. Although complex 2 exhibited longer wavelength absorption, its photocatalytic activation for the CO 2 reduction was lower than that of 1, due to the effect of conjugated linkage on the reduction potential and low emission quantum yield.

Towards New Molecular Photocatalysts for CO2 Reduction: Photo‐Induced Electron Transfer versus CO Dissociation within [Os(NN)(CO)2Cl2] Complexes

Optical excitation in the visible region of trans-(Cl)-[Os(bpy)(CO)(2)Cl(2)] (bpy=2,2'-bipyridine; C1) and trans-(Cl)-[Os(dmbpy)(CO)(2)Cl(2)] (dmbpy=4,4'-dimethyl 2,2'-bipyridine; C2) is known to induce the common CO dissociation reaction. However, the quantum yield of the reactions is less than 0.15, although C1 and C2 display pronounced photoluminescence in the visible region at room temperature with a lifetime of few tens of nanoseconds. Taking into account the characteristics of their emitting state, we have investigated the capability of C1 and C2 to act as a photosensitiser in redox reactions in different solvents (MeCN, PrCN and DMF). The efficient oxidation and reduction of both complexes under continuous irradiation in the presence of a sacrificial electron acceptor or donor is reported here. The photo-induced transformations and the nature of the resulting compounds were analysed by UV/Vis and IR spectroscopies and cyclic voltammetry. Photo-induced oxidation of C1 and C2 leads to the corresponding monocarbonyl oxidised species, whereas photo-induced reduction under argon leads mainly to the formation of the corresponding Os-bonded molecular wires P1 and P2 after exchange of two electrons associated with the loss of two chloro ligands. The chemical yield of the latter reaction (around 65%) becomes quantitative by adding [Ru(bpy)(3)](2+) as an external redox photosensitiser. This behaviour has been used to photocatalyse the two electron, two proton conversion of CO(2) to CO. Turnover numbers (TON) of 11.5 and 19.5 have been obtained respectively for C1 and C2 after 4.5 h of irradiation under CO(2) in DMF with triethanolamine as the electron donor. TON can be slightly increased by adding [Ru(bpy)(3)](2+) to the solution.