Photogeneration of Carbon Monoxide and of Hydrogen via Simultaneous Photochemical Reduction of Carbon Dioxide and Water by Visible-Light Irradiation of Organic Solutions Containing Tris(2,2′-bipyridine)ruthenium(II) and Cobalt(II) Species as Homogeneous Catalysts

CO and H₂ are photogenerated simultaneously by visible-light irradiation of systems containing a photosensitizer, the [Ru(bpy)₃]²⁺ complex, Co(II) species as homogeneous catalysts, which mediate CO₂ and H₂O reduction by intermediate formation of Co(I), a tertiary amine as electron donor, which provides the electrons for the reduction, and an organic solvent which also facilitates dissolution of CO₂. The efficiency of (CO + H₂) gas production and the selectivity CO/H₂ markedly depend upon the composition of the medium, the nature of the tertiary amine, the solvent, and the ligand of the Co ions. 2,9-Dimethyl-1,10-phenanthroline is particularly effective in promoting CO and H₂ formation, giving a quantum yield of 7.7% in (CO + H₂) (1.2% for CO and 6.5% for H₂). The process consists of two catalytic cycles: a photocatalytic cycle for the Ru complex and a double dark reaction pathway for the Co species; oxidative and/or reductive quenching of the excited state of the photosensitizer lead to the formation of Co(I) species which reduce either CO₂ or H₂O to CO or H₂, respectively.     

POM-Incorporated CoO Nanowires for Enhanced Photocatalytic Syngas Production from CO2

Utilizing sustainable energy for chemical activation of small molecules, such as CO₂, to produce important chemical feedstocks is highly desirable. The simultaneous production of CO/H₂ mixture (syngas) from photoreduction of CO₂ and H₂O is highly promising. However, the relationships between structure, composition, crystallinity, and photocatalytic performance are still indistinct. Here, amorphous ultrathin CoO nanowires and polyoxometalate incorporated nanowires with even lower crystallinity were synthesized. The POM-incorporated ultrathin nanowires exhibit high photocatalytic syngas production activity, reaching H₂ and CO evolution rates of 11555 and 4165 μmol g⁻¹ h⁻¹ respectively. Further experiments indicate that the ultrathin morphology and incorporation of POM both contribute to the superior performance. Multiple characterizations reveal the enhanced charge–hole separation efficiency of the catalyst would facilitate the photocatalysis.     

POM‐Incorporated CoO Nanowires for Enhanced Photocatalytic Syngas Production from CO2

Utilizing sustainable energy for chemical activation of small molecules, such as CO₂, to produce important chemical feedstocks is highly desirable. The simultaneous production of CO/H₂ mixture (syngas) from photoreduction of CO₂ and H₂O is highly promising. However, the relationships between structure, composition, crystallinity, and photocatalytic performance are still indistinct. Here, amorphous ultrathin CoO nanowires and polyoxometalate incorporated nanowires with even lower crystallinity were synthesized. The POM‐incorporated ultrathin nanowires exhibit high photocatalytic syngas production activity, reaching H₂ and CO evolution rates of 11555 and 4165 μmol g^?1 h^?1 respectively. Further experiments indicate that the ultrathin morphology and incorporation of POM both contribute to the superior performance. Multiple characterizations reveal the enhanced charge–hole separation efficiency of the catalyst would facilitate the photocatalysis.     

Selective CO2-to-Syngas Conversion Enabled by Bimetallic Gold/Zinc Sites in Partially Reduced Gold/Zinc Oxide Arrays

Electrocatalytic CO₂-to-syngas (gaseous mixture of CO and H₂) is a promising way to curb excessive CO₂ emission and the greenhouse gas effect. Herein, we present a bimetallic AuZn@ZnO (AuZn/ZnO) catalyst with high efficiency and durability for the electrocatalytic reduction of CO₂ and H₂O, which enables a high Faradaic efficiency of 66.4 % for CO and 26.5 % for H₂ and 3 h stability of CO₂-to-syngas at −0.9 V vs. the reversible hydrogen electrode (RHE). The CO/H₂ ratios show a wide range from 0.25 to 2.50 over a narrow potential window (−0.7 V to −1.1 V vs. RHE). In situ attenuated total reflection surface-enhanced infrared absorption spectroscopy combined with density functional theory calculations reveals that the bimetallic synergistic effect between Au and Zn sites lowers the activation energy barrier of CO₂ molecules and facilitates electronic transfer, further highlighting the potential to control CO/H₂ ratios for efficient syngas production using the coexisting Au sites and Zn sites.     

Dual Ag/Co cocatalyst synergism for the highly effective photocatalytic conversion of CO2 by H2O over Al-SrTiO3

Loading Ag and Co dual cocatalysts on Al-doped SrTiO₃ (AgCo/Al-SrTiO₃) led to a significantly improved CO-formation rate and extremely high selectivity toward CO evolution (99.8%) using H₂O as an electron donor when irradiated with light at wavelengths above 300 nm. Furthermore, the CO-formation rate over AgCo/Al-SrTiO₃ (52.7 μmol h⁻¹) was a dozen times higher than that over Ag/Al-SrTiO₃ (4.7 μmol h⁻¹). The apparent quantum efficiency for CO evolution over AgCo/Al-SrTiO₃ was about 0.03% when photoirradiated at a wavelength at 365 nm, with a CO-evolution selectivity of 98.6% (7.4 μmol h⁻¹). The Ag and Co cocatalysts were found to function as reduction and oxidation sites for promoting the generation of CO and O₂, respectively, on the Al-SrTiO₃ surface.

Deposition Ag and Co dual cocatalysts onto Al-SrTiO₃ significantly improves its activity for photoreduction of CO₂ by H₂O, with extremely high selectivity to CO evolution (99.8%), in which Ag and Co enable CO₂ reduction and H₂O oxidation, respectively.     

Enhancing photocatalytic performance of metal-organic frameworks for CO2 reduction by a bimetallic strategy

Metal-organic frameworks（MOFs） as a type of crystalline heterogeneous catalysts have shown potential application in photocatalytic CO₂ reduction.However,MOF catalysts with high efficiency and selectivity are still in pursuit.Herein,by a bimetallic strategy,the catalytic performance of a Co-MOF for photocatalytic CO₂ reduction was enhanced.Specifically,the Co-MOF based on 4,5-dicarboxylic acid（H₃ IDC） and4,4’-bipydine（4,4’-bpy） can catalyze CO₂ reductio...     

H2 production with low CO selectivity from photocatalytic reforming of glucose on metal/TiO2 catalysts

H₂ with low CO concentration is produced via photocatalytic reforming of glucose (as a representative of biomass component) on metal/TiO₂ catalyst (metals: Pt, Rh, Ru, Ir, Au, Ni, Cu). It is shown that the loaded metals generally enhance the rate of H₂ production, while they depress the CO selectivity. Both H₂ production and CO selectivity are strongly dependent on the kind of deposited metals on TiO₂. For example, Rh/TiO₂ catalyst is found to be most active for H₂ production while with the most extremely low CO concentration from the photocatalytic reforming of glucose.     

Site Isolation Leads to Stable Photocatalytic Reduction of CO2 over a Rhenium‐Based Catalyst

A porous organic polymer incorporating [(α‐diimine)Re(CO)₃Cl] moieties was produced and tested in the photocatalytic reduction of CO₂, with NEt₃ as a sacrificial donor. The catalyst generated both H₂ and CO, although the Re moiety was not required for H₂ generation. After an induction period, the Re‐containing porous organic polymer produced CO at a stable rate, unless soluble [(bpy)Re(CO)₃Cl] (bpy=2,2′‐bipyridine) was added. This provides the strongest evidence to date that [(α‐diimine)Re(CO)₃Cl] catalysts for photocatalytic CO₂ reduction decompose through a bimetallic pathway.     

An amide-based second coordination sphere promotes the dimer pathway of Mn-catalyzed CO2-to-CO reduction at low overpotential

The [fac-Mn(bpy)(CO)₃Br] complex is capable of catalyzing the electrochemical reduction of CO₂ to CO with high selectivity, moderate activity and large overpotential. Several attempts have been made to lower the overpotential and to enhance the catalytic activity of this complex by manipulating the second-coordination sphere of manganese and using relatively stronger acids to promote the protonation-first pathway. We report herein that the complex [fac-Mn(bpy-CONHMe)(CO)₃(MeCN)]⁺ ([1-MeCN]⁺; bpy-CONHMe = N-methyl-(2,2′-bipyridine)-6-carboxamide) as a pre-catalyst could catalyze the electrochemical reduction of CO₂ to CO with low overpotential and high activity and selectivity. Combined experimental and computational studies reveal that the amide NH group not only decreases the overpotential of the Mn catalyst by promoting the dimer and protonation-first pathways in the presence of H₂O but also enhances the CO₂ electroreduction activity by facilitating C–OH bond cleavage, making [1-MeCN]⁺ an efficient CO₂ reduction pre-catalyst at low overpotential.

The amide NH group decreases the overpotential of Mn-based CO₂ reduction catalysts by promoting the dimer and protonation-first pathways in the presence of H₂O and enhances the CO₂ electroreduction activity by facilitating C–OH bond cleavage.     

Electrothermal Water-Gas Shift Reaction at Room Temperature with a Silicomolybdate-Based Palladium Single-Atom Catalyst

The water-gas shift (WGS) reaction is often conducted at elevated temperature and requires energy-intensive separation of hydrogen (H₂) from methane (CH₄), carbon dioxide (CO₂), and residual carbon monoxide (CO). Designing processes to decouple CO oxidation and H₂ production provides an alternative strategy to obtain high-purity H₂ streams. We report an electrothermal WGS process combining thermal oxidation of CO on a silicomolybdic acid (SMA)-supported Pd single-atom catalyst (Pd₁/CsSMA) and electrocatalytic H₂ evolution. The two half-reactions are coupled through phosphomolybdic acid (PMA) as a redox mediator at a moderate anodic potential of 0.6 V (versus Ag/AgCl). Under optimized conditions, our catalyst exhibited a TOF of 1.2 s⁻¹ with turnover numbers above 40 000 mol mol_Pd⁻¹ achieving stable H₂ production with a purity consistently exceeding 99.99 %.     

Nanocomposites of Tantalum‐Based Pyrochlore and Indium Hydroxide Showing High and Stable Photocatalytic Activities for Overall Water Splitting and Carbon Dioxide Reduction

Nanocomposites of tantalum‐based pyrochlore nanoparticles and indium hydroxide were prepared by a hydrothermal process for UV‐driven photocatalytic reactions including overall water splitting, hydrogen production from photoreforming of methanol, and CO₂ reduction with water to produce CO. The best catalyst was more than 20 times more active than sodium tantalate in overall water splitting and 3 times more active than Degussa P25 TiO₂ in CO₂ reduction. Moreover, the catalyst was very stable while generating stoichiometric products of H₂ (or CO) and O₂ throughout long‐term photocatalytic reactions. After the removal of In(OH)₃, the pyrochlore nanoparticles remained highly active for H₂ production from pure water and aqueous methanol solution. Both experimental studies and density functional theory calculations suggest that the pyrochlore nanoparticles catalyzed the water reduction to produce H₂, whereas In(OH)₃ was the major active component for water oxidation to produce O₂.     

H2 production with low CO selectivity from photocatalytic reforming of glucose on metal/TiO2 catalysts

H₂ with low CO concentration is produced via photocatalytic reforming of glucose (as a representative of biomass component) on metal/TiO₂ catalyst (metals: Pt, Rh, Ru, Ir, Au, Ni, Cu). It is shown that the loaded metals generally enhance the rate of H₂ production, while they depress the CO selectivity. Both H₂ production and CO selectivity are strongly dependent on the kind of deposited metals on TiO₂. For example, Rh/TiO₂ catalyst is found to be most active for H₂ production while with the most extremely low CO concentration from the photocatalytic reforming of glucose. Supported by the National Natural Science Foundation of China (Grant No. 20403018, 20503034), National Basic Research Program of China (Grant No. 2003CB214504), and Knowledge Innovation Program of the Chinese Academy of Sciences (DICP K2006E2)     

Cu、N共掺杂TiO2纳米管光催化重整甘油制备合成气

通过碱性水热-离子交换法制备了Cu、N共掺杂TiO₂纳米管(Cu/N-TNT),对其光催化重整甘油制备合成气性能进行了研究。结果表明,Cu/N-TNT具有富含氧空位(O_v)的管状结构,N以Ti-N形式取代部分O形成杂质能级,Cu以Cu²⁺形式掺杂在催化剂晶格间隙和表面,Cu、N共掺杂促进TiO₂表面电荷有效分离,有利于其光催化重整甘油制备合成气活性和选择性的提高。紫外光照射8h时,掺Cu量为0.15%的Cu/N-TNT催化剂上CO和H₂产量分别为7.3和8.5 mmol·g^-1,是原始TiO₂的9.1和70.8倍,n_H2/n_CO从0.52提高为1.18,n_CO/n_CO2从0.21提高至0.42。Cu/N-TNT表面N和O_V为醛类脱羰和甲酸脱水生成CO提供反应活性位点,Cu作为浅势阱提...     

A study on methanol steam reforming to CO2 and H2 over the La2CuO4 nanofiber catalyst

The La₂CuO₄ crystal nanofibers were prepared by using single-walled carbon nanotubes as templates under mild hydrothermal conditions. The steam reforming of methanol (SRM) to CO₂ and H₂ over such nanofiber catalysts was studied. At the low temperature of 150 °C and steam/methanol=1.3, methanol was completely (100%, 13.8 g/h g catalyst) converted to hydrogen and CO₂ without the generation of CO. Within the 60 h catalyst lifespan test, methanol conversion was maintained at 98.6% (13.6 g/h g catalyst) and with 100% CO₂ selectivity. In the meantime, for distinguishing the advantage of nanoscale catalyst, the La₂CuO₄ bulk powder was prepared and tested for the SRM reaction for comparison. Compared with the La₂CuO₄ nanofiber, the bulk powder La₂CuO₄ showed worse catalytic activity for the SRM reaction. The 100% conversion of methanol was achieved at the temperature of 400 °C, with the products being H₂ and CO₂ together with CO. The catalytic activity in terms of methanol conversion dropped to 88.7% (12.2 g/h g catalyst) in 60 h. The reduction temperature for nanofiber La₂CuO₄ was much lower than that for the La₂CuO₄ bulk powder. The nanofibers were of higher specific surface area (105.0 m²/g), metal copper area and copper dispersion. The in situ FTIR and EPR experiments were employed to study the catalysts and catalytic process. In the nanofiber catalyst, there were oxygen vacancies. H₂-reduction resulted in the generation of trapped electrons [e] on the vacancy sites. Over the nanofiber catalyst, the intermediate H₂CO/HCO was stable and was reformed to CO₂ and H₂ by steam rather than being decomposed directly to CO and H₂. Over the bulk counterpart, apart from the direct decomposition of H₂CO/HCO to CO and H₂, the intermediate H₂COO might go through two decomposition ways: H₂COO=CO+H₂O and H₂COO=CO₂+H₂.     

Electrocatalytic CO2 Reduction with a Half‐Sandwich Cobalt Catalyst: Selectivity towards CO

We present herein a Cp*Co(III)‐half‐sandwich catalyst system for electrocatalytic CO₂ reduction in aqueous acetonitrile solution. In addition to an electron‐donating Cp* ligand (Cp*=pentamethylcyclopentadienyl), the catalyst featured a proton‐responsive pyridyl‐benzimidazole‐based N,N‐bidentate ligand. Owing to the presence of a relatively electron‐rich Co center, the reduced Co(I)‐state was made prone to activate the electrophilic carbon center of CO₂. At the same time, the proton‐responsive benzimidazole scaffold was susceptible to facilitate proton‐transfer during the subsequent reduction of CO₂. The above factors rendered the present catalyst active toward producing CO as the major product over the other potential 2e/2H⁺ reduced product HCOOH, in contrast to the only known similar half‐sandwich CpCo(III)‐based CO₂‐reduction catalysts which produced HCOOH selectively. The system exhibited a Faradaic efficiency (FE) of about 70% while the overpotential for CO production was found to be 0.78 V, as determined by controlled‐potential electrolysis.     

Coupling Benzylamine Oxidation with CO2 Photoconversion to Ethanol over a Black Phosphorus and Bismuth Tungstate S-Scheme Heterojunction

Photoconversion of CO₂ and H₂O into ethanol is an ideal strategy to achieve carbon neutrality. However, the production of ethanol with high activity and selectivity is challenging owing to the less efficient reduction half-reaction involving multi-step proton-coupled electron transfer (PCET), a slow C−C coupling process, and sluggish water oxidation half-reaction. Herein, a two-dimensional/two-dimensional (2D/2D) S-scheme heterojunction consisting of black phosphorus and Bi₂WO₆ (BP/BWO) was constructed for photocatalytic CO₂ reduction coupling with benzylamine (BA) oxidation. The as-prepared BP/BWO catalyst exhibits a superior photocatalytic performance toward CO₂ reduction, with a yield of 61.3 μmol g⁻¹ h⁻¹ for ethanol (selectivity of 91 %).In situ spectroscopic studies and theoretical calculations reveal that S-scheme heterojunction can effectively promote photogenerated carrier separation via the Bi−O−P bridge to accelerate the PCET process. Meanwhile, electron-rich BP acts as the active site and plays a vital role in the process of C−C coupling. In addition, the substitution of BA oxidation for H₂O oxidation can further enhance the photocatalytic performance of CO₂ reduction to C₂H₅OH. This work opens a new horizon for exploring novel heterogeneous photocatalysts in CO₂ photoconversion to C₂H₅OH based on cooperative photoredox systems.     

Thermal desorption in catalytic systems 13. The surface adsorption of H2O,CO, and CO2 on copper oxide-zinc-aluminum-calcium catalysts for low-temperature conversion of carbon monoxide

Conclusions The relation between the thermodesorption parameters for Co, CO₂, and H₂O and the activity of copper oxide-zinc-aluminum-calcium catalysts has been discussed. It is suggested that high catalytic activity is associated with high CO, and low CO₂ and H₂O, adsorption on the nonuniform surface. The thermodesorption parameters are determined by the oxidation-reduction treatment to which the catalyst has been subjected.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2233–2238, October, 1978.For Communication 12, cf. [1].     

Low temperature methanation of CO2 over an amorphous cobalt-based catalyst

CO₂ methanation is an important reaction in CO₂ valorization. Because of the high kinetic barriers, the reaction usually needs to proceed at higher temperature (>300 °C). High-efficiency CO₂ methanation at low temperature (<200 °C) is an interesting topic, and only several noble metal catalysts were reported to achieve this goal. Currently, design of cheap metal catalysts that can effectively accelerate this reaction at low temperature is still a challenge. In this work, we found that the amorphous Co–Zr_0.1–B–O catalyst could catalyze the reaction at above 140 °C. The activity of the catalyst at 180 °C reached 10.7 mmol_CO2 g_cat⁻¹ h⁻¹, which is comparable to or even higher than that of some noble metal catalysts under similar conditions. The Zr promoter in this work had the highest promoting factor to date among the catalysts for CO₂ methanation. As far as we know, this is the first report of an amorphous transition metal catalyst that could effectively accelerate CO₂ methanation. The outstanding performance of the catalyst could be ascribed to two aspects. The amorphous nature of the catalyst offered abundant surface defects and intrinsic active sites. On the other hand, the Zr promoter could enlarge the surface area of the catalyst, enrich the Co atoms on the catalyst surface, and tune the valence state of the atoms at the catalyst surface. The reaction mechanism was proposed based on the control experiments.

It is discovered that an amorphous transition metal catalyst Co–Zr0.1–B–O could effectively accelerate CO2 methanation, at a rate that is comparable to or even higher than that of some noble metal catalysts under similar conditions.     

Rational Design of Crystalline Covalent Organic Frameworks for Efficient CO2 Photoreduction with H2O

Solar energy‐driven conversion of CO₂ into fuels with H₂O as a sacrificial agent is a challenging research field in photosynthesis. Herein, a series of crystalline porphyrin‐tetrathiafulvalene covalent organic frameworks (COFs) are synthesized and used as photocatalysts for reducing CO₂ with H₂O, in the absence of additional photosensitizer, sacrificial agents, and noble metal co‐catalysts. The effective photogenerated electrons transfer from tetrathiafulvalene to porphyrin by covalent bonding, resulting in the separated electrons and holes, respectively, for CO₂ reduction and H₂O oxidation. By adjusting the band structures of TTCOFs, TTCOF‐Zn achieved the highest photocatalytic CO production of 12.33 μmol with circa 100 % selectivity, along with H₂O oxidation to O₂. Furthermore, DFT calculations combined with a crystal structure model confirmed the structure–function relationship. Our work provides a new sight for designing more efficient artificial crystalline photocatalysts.     

Rational Design of Polymers for Selective CO2 Reduction Catalysis

A series of copolymers comprising a terpyridine ligand and various functional groups were synthesized toward integrating a Co‐based molecular CO₂ reduction catalyst. Using porous metal oxide electrodes designed to host macromolecules, the Co‐coordinated polymers were readily immobilized via phosphonate anchoring groups. Within the polymeric matrix, the outer coordination sphere of the Co terpyridine catalyst was engineered using hydrophobic functional moieties to improve CO₂ reduction selectivity in the presence of water. Electrochemical and photoelectrochemical CO₂ reduction were demonstrated with the polymer‐immobilized hybrid cathodes, with a CO:H₂ product ratio of up to 6:1 compared to 2:1 for a corresponding “monomeric” Co terpyridine catalyst. This versatile platform of polymer design demonstrates promise in controlling the outer‐sphere environment of synthetic molecular catalysts, analogous to CO₂ reductases.