Visible light driven photo-reduction of Cu2+ to Cu2O to Cu in water for photocatalytic hydrogen production

A visible-light-driven system for photoreduction of Cu(ii) to Cu₂O to Cu(0) and identification of Cu(0) as the active catalyst for hydrogen production.

An Unexpected Iron (II)-Based Homogeneous Catalytic System for Highly Efficient CO2-to-CO Conversion under Visible-Light Irradiation

We present two as-synthesized Fe(II)-based molecular catalysts with 1,10-phenanthroline (phen) ligands; Fe(phen)₃Cl₂ (1) and [Fe(phen)₂(CH₃CH₂OH)Cl]Cl (2), and their robust catalytic properties for the conversion of CO₂ to CO in DMF/TEOA (DMF = N,N’-dimethylformamide; TEOA = triethanolamine) solution containing Ru(bpy)₃²⁺ and BIH (1,3-dimethyl-2-phenyl-2,3- dihydro-1H-benzo-[d]-imidazole). High turnover numbers (TONs) of 19,376 were achieved with turnover frequencies (TOFs) of 3.07 s⁻¹ for complex 1 (1.5 × 10⁻⁷ M). A quantum efficiency of 0.38% was observed after 5 h irradiated by 450 nm monochromatic light. The generation rate of CO₂ and H₂ were tuned by optimizing the experimental conditions, resulting in a high CO selectivity of 90%. The remarkable contribution of the photosensitizer to the total TON_CO was found being 19.2% (as shown by tests under similar conditions without catalysts) when BIH was employed as a sacrificial electron donor. The product selectivity in complex 2 reached 95%, and the corresponding TON_CO and TOF_CO were 33,167 and 4.61 s⁻¹ in the same concentration with complex 1 used as catalyst; respectively. This work provides guidance for future designs of simple, highly efficient and selective molecular catalytic systems that facilitate carbon-neutral solar-to-fuel conversion processes

Highly efficient photocatalytic reduction of CO2 to CO using cobalt oxide-coated spherical mesoporous silica particles as catalysts

Hybrid catalysts that cobalt oxide nanoparticles immobilized on outside surfaces of spherical SBA-15 presented unexpected photocatalytic activity towards CO₂-to-CO conversion.

Cu(OH)2 supported on Fe(OH)3 as a synergistic and highly efficient system for the dehydrogenation of ammonia-borane

Herein, we first describe the physical mixture of Cu(OH)₂/Fe(OH)₃ as a composite catalyst precursor for the dehydrogenation of ammonia borane (AB) in methanol. During the initial period of catalytic reaction, Cu nanoparticles were formed in-situ. The catalytic activity of Cu nanoparticles can be significantly enhanced with the assistance of Fe species and OH^-. A maximum turnover frequency (TOF) of 50.3 mol_H2 mol_{total metal}^-1 min^-1 (135.6 mol_H2 mol_Cu^-1 min^-1) was achieved at ambient temperature, which is superior to those of previously reported Fe or Cu based systems.

In Situ Preparation of CoP@CdS and Its Catalytic Activity toward Controlling Nitro Reduction under Visible-Light Irradiation

CoP was synthesized in situ on the surface of CdS nanowires using a cobalt-ammine complex as a precursor. The generated CoP@CdS photocatalyst was well characterized by X-ray diffraction, transmission electron microscopy, selected-area electron diffraction, and diffuse reflectance spectra. A more efficient charge transfer was successfully achieved owing to the close contact between CoP and CdS. The hybrid photocatalyst showed excellent activity for the reduction of nitroarenes to the corresponding anilines or azobenzene compounds in water. In present work, hydrogen evolution and nitro reduction were concurrent and with the consumption of substrate, the rate of hydrogen evolution increased. The driving force for the reduction originated from the activated hydrogen species in the photocatalytic reaction rather than from dihydrogen. The photocatalytic activity of as-prepared CoP@CdS in situ is comparable to that of the catalysts formed using a noble metal loaded onto CdS. Mechanistic investigation showed that the condensation route is the major pathway for nitro reduction in the present system, and azo compounds could be obtained with less irradiation time, while aniline will be obtained via long-time irradiation.

Interstitial P-Doped CdS with Long-Lived Photogenerated Electrons for Photocatalytic Water Splitting without Sacrificial Agents

Photocatalytic hydrogen evolution from pure water is successfully realized by using interstitial P-doped CdS with rich S vacancies (CdS-P) as the photocatalyst in the absence of any electron sacrificial agents. Through interstitial P doping, the impurity level of S vacancies is located near the Fermi level and becomes an effective electron trap level in CdS-P, which can change dynamic properties of photogenerated electrons and thus prolong their lifetimes. The long-lived photogenerated electrons are able to reach the surface active sites to initiate an efficient photocatalytic redox reaction. Moreover, the photocatalytic activity of CdS-P can be further improved through the loading of CoP as a cocatalyst.

Photocatalytic oxidation of arylalcohols to aromatic aldehydes promoted by hydroxyl radicals over a CoP/CdS photocatalyst in water with hydrogen evolution

Hydroxyl free radicals generated by visible-light-catalyzed water splitting over CoP/CdS drive the oxidation of arylalcohols with hydrogen evolution.

Heteroporous MoS2/Ni3S2 towards superior electrocatalytic overall urea splitting

The heteroporous MoS₂/Ni₃S₂ catalyst exhibits the best activity for urea splitting of all the bifunctional electrocatalysts, including Pt, reported until now.

Metal Phosphides as Co-Catalysts for Photocatalytic and Photoelectrocatalytic Water Splitting

Solar-to-hydrogen conversion based on photocatalytic and photoelectrocatalytic water splitting is considered as a promising technology for sustainable hydrogen production. Developing earth-abundant H₂ -production materials with robust activity and stability has become the mainstream in this field. Due to the unique properties and characteristics, transition metal phosphides (TMPs) have been proven to be high performance co-catalysts to replace some of the classic precious metal materials in photocatalytic water splitting. In this Minireview, we summarize the recent significant progress of TMPs as cocatalysts for water splitting reaction with high activity and stability. Firstly, the characteristic of TMPs is briefly introduced. Then, we mainly discuss the recent research efforts toward their application as photocatalytic co-catalysts in photocatalytic H₂ -production, O₂ -evolution and photoelectrochemical water splitting. Finally, the catalytic mechanism, current existing challenges and future working directions for improving the performance of TMPs are proposed.

Highly selective oxidation of sulfides on a CdS/C3N4 catalyst with dioxygen under visible-light irradiation

A CdS/C₃N₄ visible-light catalyst exhibits high product selectivity towards photocatalytic oxidation of sulfides into corresponding sulfoxides with dioxygen in methanol.

Highly efficient hydrolysis of ammonia borane by anion (−OH, F−, Cl−)-tuned interactions between reactant molecules and CoP nanoparticles

An anion-assisted hydrolytic H₂-releasing ultra-high performance system involving ammonia borane and a CoP nanoparticle catalyst has been established under ambient conditions.

Self-Supported Cedarlike Semimetallic Cu3P Nanoarrays as a 3D High-Performance Janus Electrode for Both Oxygen and Hydrogen Evolution under Basic Conditions

There has been strong and growing interest in the development of cost-effective and highly active oxygen evolution reaction (OER) electrocatalysts for alternative fuels utilization and conversion devices. We report herein that semimetallic Cu3P nanoarrays directly grown on 3D copper foam (CF) substrate can function as effective electrocatalysts for water oxidation. Specifically, the surface oxidation-activated Cu3P only required a relatively low overpotential of 412 mV to achieve a current density of 50 mA cm(-2) and displayed a small Tafel slope of 63 mV dec(-1) in 0.1 M KOH solution, on account of the collaborative effect of large roughness factor (RF) and semimetallic character. Following that, investigations into the mechanism revealed the formation of a unique active phase during the water oxidation process in which conductive Cu3P was the core covered with a thin copper oxide/hydroxide layer. Moreover, this Cu3P 3D electrode was also applied to the hydrogen evolution reaction (HER) and showed good catalytic performance and stability under the same basic conditions.

Self-Supported Cu-Based Nanowire Arrays as Noble-Metal-Free Electrocatalysts for Oxygen Evolution

Crystalline Cu-based nanowire arrays (NWAs) including Cu(OH)2 , CuO, Cu2 O, and CuOx are facilely grown on Cu foil and are found to act as highly efficient, low-cost, and robust electrocatalysts for the oxygen evolution reaction (OER). Impressively, this noble-metal-free 3 D Cu(OH)2 -NWAs/Cu foil electrode shows the highest catalytic activity with a Tafel slope of 86 mV dec(-1) , an overpotential (η) of about 530 mV at ∼10 mA cm(-2) (controlled-potential electrolysis method without iR correction) and almost 100 % Faradic efficiency, paralleling the performance of the state-of-the-art RuO2 OER catalyst in 0.1 m NaOH solution (pH 12.8). To the best of our knowledge, this work represents one of the best results ever reported on Cu-based OER systems.

Robustly photogenerating H2 in water using FeP/CdS catalyst under solar irradiation

Photosplitting water for H₂ production is a promising, sustainable approach for solar-to-chemical energy conversion. However, developing low-cost, high efficient and stable photocatalysts remains the major challenge. Here we report a composite photocatalyst consisting of FeP nanoparticles and CdS nanocrystals (FeP/CdS) for photogenerating H₂ in aqueous lactic acid solution under visible light irradiation. Experimental results demonstrate that the photocatalyst is highly active with a H₂-evolution rate of 202000 μmol h⁻¹ g⁻¹ for the first 5 h (106000 μmol h⁻¹ g⁻¹ under natural solar irradiation), which is the best H₂ evolution activity, even 3-fold higher than the control in situ photo-deposited Pt/CdS system, and the corresponding to an apparent quantum efficiency of over 35% at 520 nm. More important, we found that the system exhibited excellent stability and remained effective after more than 100 h in optimal conditions under visible light irradiation. A wide-ranging analysis verified that FeP effectively separates the photoexcited charge from CdS and showed that the dual active sites in FeP enhance the activity of FeP/CdS photocatalysts.

Rapid synthesis of ultralong Fe(OH)3:Cu(OH)2 core–shell nanowires self-supported on copper foam as a highly efficient 3D electrode for water oxidation

Ultralong Fe(OH)₃:Cu(OH)₂ core–shell nanowires were facilely grown on an open 3D Cu electrode to function as a highly efficient electrocatalyst for water oxidation.

Ultrafine CoP Nanoparticles Supported on Carbon Nanotubes as Highly Active Electrocatalyst for Both Oxygen and Hydrogen Evolution in Basic Media

The development of low-cost and highly active electrocatalysts for two half reactions: H2 and O2 evolution reactions (HER and OER), is still a huge challenge to realize water splitting. Herein, we report that CoP nanoparticles (NPs) can act as a bifunctional catalyst for both HER and OER. Particularly, ultrafine CoP NPs decorated on N-doped multiwalled carbon nanotube (MWCNT) exhibit remarkable catalytic performance for OER in 0.1 M NaOH aqueous solution, with a low onset overpotential of 290 mV, a Tafel slope of 50 mV dec(-1), an overpotential (η) of 330 mV at 10 mA cm(-2), and approximately 100% Faradaic efficiency, paralleling the performance of state-of-the-art Co-based OER catalysts including Co3O4, CoSe2, and Co-Pi. The hybrid catalyst is capable of maintaining a high catalytic current density for at least 10 h without any loss of catalytic activity. Meanwhile, the noble-metal-free catalyst also shows good activity and duarability for HER under the same basic condition.

New platinum and ruthenium Schiff base complexes for water splitting reactions

New Pt(ii) and Ru(ii) complexes with Schiff base ligands display effective visible-light catalytic water reduction and Ce⁴⁺-driven oxidation activities, respectively.

Spectacular photocatalytic hydrogen evolution using metal-phosphide/CdS hybrid catalysts under sunlight irradiation

Transition metal phosphide (CoP,Ni₂P,Cu₃P)/CdS hybrid catalysts were applied to heterogeneous photocatalytic hydrogen evolution and exhibited splendid photocatalytic activity with a H₂-production rate of up to 254 000 μmol h⁻¹ g⁻¹ and excellent stability in aqueous acidic media.

Highly efficient and selective photocatalytic reduction of nitroarenes using the Ni2P/CdS catalyst under visible-light irradiation

A highly efficient Ni₂P/CdS photocatalytic system in water for selective nitro reduction to amino organics and the reaction mechanism were presented clearly.

Long-lived excited states of zwitterionic copper(I) complexes for photoinduced cross-dehydrogenative coupling reactions

Four heteroleptic copper(I) complexes containing phenanthroline and monoanionic nido-carborane-diphosphine ligands have been prepared and structurally characterized by various spectroscopic techniques and X-ray diffraction. These complexes exhibit intense absorptions in the visible range and excited-state lifetimes on the microsecond scale. Their application in visible-light-induced cross-dehydrogenative coupling reactions was investigated. Preliminary studies showed that one of the four copper(I) complexes is an efficient catalyst for photoinduced oxidative C-H functionalization using oxygen as oxidant. Furthermore, α-functionalized tertiary amines were obtained in good-to-excellent yields by light irradiation (λ>420 nm) of a mixture of our Cu(I) complex, tertiary amines, and a variety of nucleophiles (nitroalkane, acetone, or indoles) under aerobic conditions. Electron paramagnetic resonance measurements provided evidence for the formation of superoxide radical anions (O2(-⋅)) rather than singlet oxygen ((1)O2) during these photocatalytic reactions.

New members of fluorescent 1,8-naphthyridine-based BF2 compounds: selective binding of BF2 with terminal bidentate N^N^O and N^C^O groups and tunable spectroscopy properties

Intensely luminescent 1,8-naphthyridine-BF2 complexes 1-9 containing terminal bidentate N^N^O and/or N^C^O groups are synthesized and structurally characterized by X-ray diffraction, electrospray ionization mass spectrometry, (1)H and (19)F NMR spectroscopy and elemental analysis. Complexes 1-4 are synthesized from 2-acetamino-1,8-naphthyridine derivatives by a facile route. Selective bonding modes and the chemical stability of complexes 5 and 6 obtained by reacting BF3·Et2O with 1,8-naphthyridine derivatives bearing dual-functional groups (N^C^O and N^N^O) are investigated by crystal structure analysis and time-dependent density functional theory calculations. The products containing a BF2 core bound to a N^C^O chelating group are energetically favorable and can expand the range of derivatives by substitution at the 2-position. In this regard, a free -NH2 group at the 2-position of complex 7 obtained from 5 can be functionalized under a variety of pH conditions to generate complexes 8 and 9, which bear flexible coordination arms that can be used to recognize certain transition metals. The photophysical properties of the complexes are examined in solution and solid state at room temperature. Compared with those of the starting naphthyridine-based compounds, the naphthyridine-BF2 complexes display desirable light-absorbing properties and intense solution and solid-state emission with large Stokes shifts. Complex 4 in solution exhibited an emission quantum yield of 0.98. In complexes 5-9, the binding sites for the BF2 core change from N^N^O to N^C^O, which leads to red shifts of absorption and emission, excellent chemical stability and high emission quantum yields.

Photoreduction of iron(III) to iron(0) nanoparticles for simultaneous hydrogen evolution in aqueous solution

Crystalline Fe nanoparticles were obtained with fluorescein (Fl) as the photosensitizer in triethylamine (TEA) or triethanolamine (TEOA) aqueous solution with FeCl3 as the Fe precursor under bright visible-light light-emitting diode (LED) irradiation. Photoinduced electron transfer from excited state Fl* and Fl(-) to Fe(3+) produced the Fe nanoparticles, which served as the active catalyst for in situ photocatalytic hydrogen production with Fl and TEA or TEOA as the photosensitizer and electron donors, respectively, in the same system. Robust hydrogen production activities were observed under the Fe nanoparticle photoreduction conditions in basic solution, and tens of milliliters of hydrogen were obtained over prolonged LED irradiation. If inorganic support materials such as NH2 -MCM-41 or reduced graphene oxide were introduced, dispersed nanoparticles with different sizes and shapes were deposited on the supports, which led to variously enhanced hydrogen production activities. The relationships between the morphologies of the Fe/H2 N-MCM-41 or Fe/graphene composites generated in situ and the hydrogen production activities were investigated systematically.

Facile synthesis of a ruthenium assembly and its application for light-driven oxidation of alcohols in water

A supramolecular assembly containing two light harvesting fragments [Ru(tpy)2](2+) and one catalytic unit [Ru(tpy)(bpy)Cl](+) was synthesized in a facile manner in 90% yield, and exhibited high photocatalytic product-selectivity compared with the corresponding bimolecular system in the light-driven oxidation of alcohols using [Co(NH3)5Cl]Cl2 as a sacrificial oxidant in water at room temperature.