Photocatalytic Hydrogen Evolution System Research Articles

Enhanced photocatalytic hydrogen evolution based on efficient electron transfer in triphenylamine-based dye functionalized Au@Pt bimetallic core/shell nanocomposite

An efficient photocatalytic hydrogen evolution system based on triphenylamine-based dye functionalized bimetallic Au@Pt core/shell nanocomposite (Au@Pt-TPAD) was reported. Transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV–vis absorption spectra suggested that Au@Pt-TPAD nanocomposite consisted of a bimetallic nanoparticle with Au core and Pt shell nanostructure. The photoelectrochemical result suggested that photoinduced electrons could efficiently transfer from the triphenylamine derivative molecules to the bimetallic nanoparticles. Photocatalytic results showed that the Au@Pt2-TPAD bimetallic nanocomposite could be used as a stable photoinduced H2 evolution photocatalyst. Compared with the monometallic counterpart (Au-TPAD or Pt-TPAD), the bimetallic nanocomposite showed much higher catalytic activity for the photocatalytic hydrogen evolution. The amount of hydrogen evolution on the optimal catalyst under 12 h UV–vis light irradiation was about 37.5 μmol. The enhancement of the photocatalytic activity might be attributed to the synergistic effect between the two metals in bimetallic nanoparticles with core/shell structure. This investigation might open up new opportunities for the development of dye functionalized heterometallic nanocomposite with enhanced photocatalytic performance.

Donor–acceptor porphyrin functionalized Pt nano-assemblies for artificial photosynthesis: a simple and efficient homogeneous photocatalytic hydrogen production system

In this paper, a novel porphyrin dye (5,10,15,20-tetrakis (4-(anthracene-1-ylmethoxy)phenyl) porphyrin, TPPAN) and its functionalized platinum nanoparticles (Pt-TPPAN) were synthesized. Using the Pt-TPPAN nanocomposite as a photocatalyst, a new and more compact photoinduced hydrogen evolution system from an aqueous ethanol solution without additives was developed. Fluorescence and photo-electrochemical spectra reveal that photoinduced electron transfer occurs from the photoexcited state of anthracene substituents to the porphyrin, accompanied by an electron transfer from the excited porphyrin moiety to the Pt co-catalyst. The photocatalytic activity results suggested that this TPPAN functionalized Pt nano-assembly could efficiently catalyze hydrogen evolution from an aqueous ethanol solution under simulated solar light irradiation. Therein, the TPPAN molecule in the nanocomposite worked as a light absorption antenna and the nanocore Pt species acted as a co-catalyst. This investigation might offer a new paradigm for constructing a simpler and more efficient homogeneous photocatalytic hydrogen evolution system for mimicking natural photosynthesis.

Photocatalytic Hydrogen Evolution Using 9-Phenyl-10-methyl-acridinium Ion Derivatives as Efficient Electron Mediators and Ru-Based Catalysts

Photocatalytic hydrogen evolution has been performed by photoirradiation (λ > 420 nm) of a mixed solution of a phthalate buffer and acetonitrile (MeCN) (1 : 1 (v/v)) containing EDTA disodium salt (EDTA), [RuII(bpy)3]2+ (bpy = 2,2′-bipyiridine), 9-phenyl-10-methylacridinium ion (Ph–Acr+–Me), and Pt nanoparticles (PtNPs) as a sacrificial electron donor, a photosensitiser, an electron mediator, and a hydrogen-evolution catalyst, respectively. The hydrogen-evolution rate of the reaction system employing Ph–Acr+–Me as an electron mediator was more than 10 times higher than that employing a conventional electron mediator of methyl viologen. In this reaction system, ruthenium nanoparticles (RuNPs) also act as a hydrogen-evolution catalyst as well as the PtNPs. The immobilization of the efficient electron mediator on the surface of a hydrogen-evolution catalyst is expected to enhance the hydrogen-evolution rate. The methyl group of Ph–Acr+–Me was chemically modified with a carboxy group (Ph–Acr+–CH2COOH) to interact with metal oxide surfaces. In the photocatalytic hydrogen-evolution system using Ph–Acr+–CH2COOH and Pt-loaded ruthenium oxide nanoparticles (Pt/RuO2NPs) as electron donor and hydrogen-evolution catalyst, respectively, the hydrogen-evolution rate was 1.5–2 times faster than the reaction system using Ph–Acr+–Me as an electron mediator. On the other hand, no enhancement in the hydrogen-evolution rate was observed in the reaction system using Ph–Acr+–CH2COOH with PtNPs. Thus, the enhancement of hydrogen-evolution rate originated from the favourable interaction between Ph–Acr+–CH2COOH and RuO2NPs. These results suggest that the use of Ph–Acr+–Me as an electron mediator enables the photocatalytic hydrogen evolution using PtNPs and RuNPs as hydrogen-evolution catalysts, and the chemical modification of Ph–Acr+–Me with a carboxy group paves the way to utilise a supporting catalyst, Pt loaded on a metal oxide, as a hydrogen-evolution catalyst.

Enhanced photocatalytic hydrogen evolution performance based on Ru-trisdicarboxybipyridine-reduced graphene oxide hybrid

Herein, we report an efficient photocatalytic hydrogen evolution system based on Ru-tris(dicarboxybipyridine)–reduced graphene oxide (Ru(dcbpy)3–RGO) hybrid. AFM images and UV-vis spectra validate Ru(dcbpy)3 functionalized RGO via noncovalent interactions. Fluorescence and Raman spectra suggest that Ru(dcbpy)3 acts as an electron donor and RGO serves as an electron acceptor in the hybridized species. Moreover, the photocurrent experiment further confirms that the photoelectrons transfer from Ru(dcbpy)3 to RGO nanosheets and then flow to deposited Pt nanoparticles effectively. Compared with the corresponding single-component Ru(dcbpy)3 and RGO nanosheets, the Ru(dcbpy)3–RGO hybrid displays distinctly enhanced photocatalytic activities under UV-vis or visible light irradiation. Therein, RGO acts as a solid-state electron mediator, which facilitates charge separation and suppresses recombination of photoexcited electron–hole pairs in RGO–Ru(dcbpy)3. Furthermore, the effect of reaction parameters such as pH, the composition of the hybrid and the stability of catalytic performance are also investigated. This study might initiate new possibilities for the development of novel graphene-based photocatalysts with enhanced activity via facile noncovalent modification of graphene with organic photosensitizers.

ChemInform Abstract: Graphene‐Based Photocatalytic Composites

AbstractReview: 135 refs.

Size‐ and Shape‐Dependent Activity of Metal Nanoparticles as Hydrogen‐Evolution Catalysts: Mechanistic Insights into Photocatalytic Hydrogen Evolution

The catalytic activity of Pt nanoparticles (PtNPs) with different sizes and shapes was investigated in a photocatalytic hydrogen-evolution system composed of the 9-mesityl-10-methylacridinium ion (Acr(+)-Mes: photocatalyst) and dihydronicotinamide adenine dinucleotide (NADH: electron donor), based on rates of hydrogen evolution and electron transfer from one-electron-reduced species of Acr(+)-Mes (Acr·-Mes) to PtNPs. Cubic PtNPs with a diameter of (6.3±0.6) nm exhibited the maximum catalytic activity. The observed hydrogen-evolution rate was virtually the same as the rate of electron transfer from Acr·-Mes to PtNPs. The rate constant of electron transfer (k(et)) increased linearly with increasing proton concentration. When H(+) was replaced by D(+), the inverse kinetic isotope effect was observed for the electron-transfer rate constant (k(et)(H)/k(et)(D)=0.47). The linear dependence of k(et) on proton concentration together with the observed inverse kinetic isotope effect suggests that proton-coupled electron transfer from Acr·-Mes to PtNPs to form the Pt-H bond is the rate-determining step for catalytic hydrogen evolution. When FeNPs were used instead of PtNPs, hydrogen evolution was also observed, although the hydrogen-evolution efficiency was significantly lower than that of PtNPs because of the much slower electron transfer from Acr·-Mes to FeNPs.

Self-assembled dye–layered double hydroxide–Pt nanoparticles: a novel H2 evolution system with remarkably enhanced stability

A novel photocatalytic hydrogen evolution system was constructed by using well-dispersed layered double hydroxide (LDH) to immobilize the photosensitizer (rose bengal, RB) and photocatalyst (Pt). The produced amount of H(2) from such a self-assembled RB-LDH-Pt system is a few times more than that from the Free system (without LDH). Moreover, RB-LDH-Pt can be reused for at least 6 times (still having 64% of the activity in the 6(th) run) by a simple method of centrifugation which makes this system more economical by recycling the expensive Pt. The total turnover number (TON) obtained after six runs for RB-LDH-Pt was calculated to be 304 based on Pt, which gave at least 13-fold enhancement compared with that from the Free system.

Graphene-based photocatalytic composites

The use of graphene to enhance the efficiency of photocatalysts has attracted much attention. This is because of the unique optical and electrical properties of the two-dimensional (2-D) material. This review is focused on the recent significant advances in the fabrication and applications of graphene-based hybrid photocatalysts. The synthetic strategies for the composite semiconductor photocatalysts are described. The applications of the new materials in the degradation of pollutants, photocatalytic hydrogen evolution and antibacterial systems are presented. The challenges and opportunities for the future development of graphene-based photocatalysts are also discussed.

Efficient photocatalytic hydrogen evolution without an electron mediator using a simple electron donor–acceptor dyad

A highly efficient photocatalytic hydrogen evolution system without an electron mediator such as methyl viologen (MV(2+)) has been constructed using 9-mesityl-10-methylacridinium ion (Acr(+)-Mes), poly(N-vinyl-2-pyrrolidone)-protected platinum nanoclusters (Pt-PVP) and NADH (beta-nicotinamide adenine dinucleotide, reduced form) as the photocatalyst, hydrogen evolution catalyst and electron donor, respectively. The photocatalyst (Acr(+)-Mes) undergoes photoinduced electron transfer (ET) from the Mes moiety to the singlet excited state of the Acr(+) moiety to produce an extremely long-lived ET state, which is capable of oxidizing NADH and reducing Pt-PVP, leading to efficient hydrogen evolution. The hydrogen evolution efficiency is 300 times higher than that in the presence of MV(2+) because of the much faster reduction rate of Pt-PVP by Acr(*)-Mes compared with that by MV(*+). When the electron donor (NADH) is replaced by ethanol in the presence of an alcohol dehydrogenase (ADH), NADH is regenerated during the photocatalytic hydrogen evolution.

Determination of association constants by laser flash photolysis between Zn-TPPS 3 and bipyridinium salts in photocatalytic hydrogen evolution systems

Determination of association constants by laser flash photolysis between Zn-TPPS 3 and bipyridinium salts in photocatalytic hydrogen evolution systems