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[Display omitted] • A paper-based photoanode is developed for photoelectrochemical water splitting. • MoSe 2 nanosheet anchored CdS-ZnO array functional paper is prepared. • Tandem Z-scheme configuration with double IEFs and photothermal effect are integrated. • The flexible photoanode achieves admirable solar water splitting performance. Rational design of photoelectrode architectures is deemed as an effective solution to enhance efficiency of photoelectrochemical water splitting for conquering increasingly prominent environmental problems. Herein, a programmable flexible photoanode with built-in tandem Z-scheme configuration fabricated by in-situ growth of MoSe 2 -CdS-ZnO array with ultrathin nanosheet-interlaced-nanorod structure on the Au paper electrode, is firstly reported. By taking advantages of the interwoven nanonetwork structure, high conductivity as well as larger porosity of the as-fabricated Au paper electrode, a stable light-harvesting paper chip with fast transfer/separate mediators of the charge/carriers is thus integrated. By virtue of double internal electric fields (IEFs) and photothermal effect, the developed MoSe 2 -CdS-ZnO photoanode exhibits incident-photon-to-current efficiency of 52 % under 460 nm of light irradiation, and the current density reaches 2.4 mA cm−2 at 0.3 V versus normal hydrogen electrode, which is comparable with respect to current state-of-the-art "type-II-scheme", "surface-scheme", and cocatalyst-free photocatalysts (0.03–2.4 mA cm−2). Consequently, the paper-based photoanode achieves admirable photoelectrocatalytic hydrogen generation property (39.7 μmol cm−2 h-1). The synergistic effect of tailorable tandem Z-scheme configuration with double IEFs and delineating of 3D cross-linked network structure of the proposed photoanode in this work may open an avenue for constructing high-performance photoelectrochemical water splitting devices. [ABSTRACT FROM AUTHOR]

In this paper, the Ru/RuS 2 nanoparticles as dual co-catalysts were self-assembled on the surface of g-C 3 N 4 nanotubes (Ru/RuS 2 /g-C 3 N 4 NTs) for photocatalytic H 2 production. The Ru/RuS 2 /g-C 3 N 4 NTs showed greatly enhanced photocatalytic H 2 production activity (1409 μmol·g−1·h−1), 1.16 times of RuS 2 /g-C 3 N 4 NTs (1212 μmol·h−1·g−1), 10.51 times of Ru/g-C 3 N 4 NTs (134 μmol·g−1·h−1), and 82.88 times of the pure g-C 3 N 4 NTs (17 μmol·g−1·h−1). Besides, the apparent quantum yield value (AQE) of Ru/RuS 2 /g-C 3 N 4 NTs is 3.92% at 370 nm. Ru/RuS 2 as dual co-catalysts are self-assembled on the surface of g-C 3 N 4 NTs and show strong electronic synergistic interaction between the interfaces, reduce Δ G H* of RuS 2 and desorption energy of Ru, and promote the selectivity and activity of HER kinetically and thermodynamically respectively, which exhibits higher photogenerated carrier concentration and lower charge migration resistance than RuS 2 and Ru, showing the synergistic effect to facilitate the generation and migration of carriers and provides active sites for photocatalysis. [Display omitted] • Ru/RuS 2 nanoparticles as dual co-catalysts are self-assembled on the surface of g-C 3 N 4 nanotubes. • Ru/RuS 2 /g-C 3 N 4 NTs show greatly enhanced photocatalytic H 2 production activity (1409 μmol·g−1·h−1). • Ru/RuS 2 show strong electronic synergistic interaction between the interfaces. • Ru/RuS 2 promote the selectivity and activity of HER kinetically and thermodynamically respectively. [ABSTRACT FROM AUTHOR]

Low overpotential co-catalyst is a key component for a photocatalyst in photocatalytic hydrogen generation. Dual transition metal sulfide is known as a candidate in replacing noble metal. Its property is highly dependent on its surface structure and chemical state. In this paper, we found that the hydrogen adsorption energy (ΔG H ) on various dual metal sulfide Co x Ni 4-x S 4 co-catalysts could be adjusted by variation of Co and Ni ratio. The hydrogen adsorption energies over Co and Ni sites in Co 2 Ni 2 S 4 catalyst were 548.7 and 506 kJ mol −1 respectively, while the corresponding energies over CoNi 3 S 4 and Co 3 NiS 4 catalysts were much higher than the data over Co 2 Ni 2 S 4 catalyst. It was found that the XRD peaks of (220) facet of Co x Ni 4-x S 4 shifted from 26.27° to 26.53° when Co/Ni ration varied from 3 to 1, while other facet XRD peak location did not changed, indicating surface structure of (220) facet was adjusted and could be artificially controlled. In optimized Co 2 Ni 2 S 4 co-catalyst surface, the intermediate during hydrogen formation is much more stable than over other Co x Ni 4-x S 4 co-catalyst. The surface chemical state were also controlled by Co and Ni ratio, the corresponding Co 2p 3/2 of Co x Ni 4-x S 4 @MIL-101 samples shifted to higher energy side when the Co/Ni ratio changed from 3:1 to 1:3, while Ni 2p 3/2 shifted to low energy side, which implied the composition and surface structure change leading to subtle variation of surface chemical state, as a result, it affected the properties of co-catalyst. The electrochemical and fluorescence measurement results indicated that the Co 2 Ni 2 S 4 @MIL-101 exhibited the highest transient photocurrent, the lowest overpotential (−0.33 V) and the longer fluorescence lifetime (1.49 ns). The obtained Co 2 Ni 2 S 4 @MIL-101 catalyst exhibited excellent activity for hydrogen generation (882.7 μmol H 2 in 2 h), better stability and higher apparent quantum efficiency (AQE) of ∼48.9% under visible light irradiation (>430 nm). The high photocatalytic efficiency of Co 2 Ni 2 S 4 @MIL-101 catalyst can be attributed to the low ΔG H over Co 2 Ni 2 S 4 co-catalyst, stable reaction intermediate during hydrogen formation and better photoelectrochemical properties. [ABSTRACT FROM AUTHOR]

In this paper, we systematically studied the occupation of fluorine ions on Pt(100) and Pt(111) surfaces and its effect on hydrogen-oxygen adsorption/activation and their reverse recombination, and its influence on the photocatalytic water splitting activity over the Pt(100)/TiO 2 and Pt(111)/TiO 2 photocatalyst. Base on theoretical and experimental investigation, it was found that the fluorine ions pre-adsorbed on Pt(111) achieved stronger inhibition ability of hydrogen and oxygen recombination than that on Pt(100) surface. Consequently, the photocatalytic overall water splitting activity for F/Pt(111)/TiO 2 photocatalyst was higher than that of F/Pt(100)/TiO 2 photocatalyst. • Pre-adsorbed F- induced the different degree of hydrogen and oxygen adsorption strength over Pt(100) and Pt(111) facets. • F- pre-occupation exhibited different inhibition ability on H 2 and O 2 recombination rates over Pt(100) and Pt(111) facets. • Enhanced overall water splitting activity were achieved over F pre-adsorbed F/Pt(111)/TiO 2 photocatalyst. The reversible hydrogen and oxygen recombination reaction in semiconductor dispersion highly impede the yield increase of photocatalytic water splitting to hydrogen and oxygen. In order to inhibit such reverse reaction, it is necessary to reduce the degree of hydrogen and oxygen adsorption and activiation over co-catalyst on semiconductor. It is known that partial occupation of Pt sites by halogen ions with high electronegativity can decrease the adsorption and activation degree of hydrogen and oxygen molecules over Pt/TiO 2 , by this way, hydrogen and oxygen recombination reaction can be significantly inhibited, and the overall water splitting activity can be remarkably enhanced. Nevertheless, the detail inhibition mechanism on the reverse recombination reaction by halogen ions occupation on different Pt sites is still unclear. In the present work, by comparing the fluorine ions occupation on different Pt facets, we found that the fluorine ions occupation could decrease the numbers of adsorption sites on Pt(100) and Pt(111) surface. On Pt(100) facet, a fluorine ion occupation affect the four adjacent adsorption sites for H 2 and O 2 molecules adsorption, while, on Pt(111) surface, a fluorine ion occupation could affect the six adjacent adsorption sites for H 2 and O 2 molecules adsorption. The difference of fluorine ions occupation on the Pt(100) and Pt(111) facets led to the different adsorption strength of hydrogen and oxygen molecules, which further induced the activiation difference of hydrogen and oxygen on Pt co-catalyst. The results of density functional theory (DFT) calculation indicated that the hydrogen and oxygen adsorption energies on F/Pt(100) were higher than that on F/Pt(111) surface. The H 2 /O 2 -TPD, cyclic voltammetry and in-situ XPS experimental results also verified that the hydrogen and oxygen adsorption on F/Pt(100) surface was stronger than that of F/Pt(111) surface. The hydrogen and oxygen recombination experimental results showed that the hydrogen and oxygen recombination rates over F/Pt(100) surface was higher than that of F/Pt(111) surface. Upon light irradiation, the F/Pt(100)/TiO 2 photocatalyst exhibited lower activity for overall water splitting than F/Pt(111)/TiO 2 photocatalyst. Results in this paper provide a new avenue to promote seimiconductor catalyst for over-all water splitting by tuning the adsorption sites of hydrogen and oxygen on co-catalyst surface. [ABSTRACT FROM AUTHOR]

Developing alkaline hydrogen evolution reaction catalysts with ultra-low overpotential remains a significant challenge. In this paper, a three-dimensional porous Ru/α-MoC has been developed, which features the dual active sites of α-MoC and Ru. The coexistence of ultrafine Ru nanoparticles and Ru single atoms in Ru/α-MoC system is demonstrated by multiple structural characterizations. The fabricated Ru/α-MoC exhibits excellent alkaline HER activity with a low overpotential 25 mV at 10 mA cm−2, outperforming commercial 20% Pt/C (45 mV), and robust electrocatalytic stability at an industrial-scale current density of 400 mA cm−2. Particularly, the turnover frequency value reaches 39.2 s−1 at the overpotential of 100 mV. Experiments and theory investigations demonstrate the electron redistribution at the interface of α-MoC and Ru. The synergistic effect of dual active sites enables the easy cleavage of H-OH bond and the optimal H adsorption energy simultaneously. This work opens up a feasible way to rationally design high-efficient electrocatalysts with dual active sites for typical multistep reactions. The three-dimensional porous Ru/α-MoC with dual active sites as HER electrocatalyst achieves ultralow overpotential at alkaline media. The excellent activity origin is the synergistic effect of dual active sites that facilitate water dissociation and weaken the H adsorption free energy, resulting in an accelerated reaction kinetics for alkaline hydrogen generation. [Display omitted] • High dispersed Ru species are anchored on α-MoC to construct Ru/α-MoC nanocomposites with dual active sites. • Ru/α-MoC interfaces afford remarkably promoted alkaline HER performance. • The synergistic effect of dual active sites at the interfaces enables the easy cleavage of H-OH bond and the optimal H adsorption energy simultaneously. [ABSTRACT FROM AUTHOR]

Cu 2 O is a p-type semiconductor which attracts much attention for application in photovoltaics, photocatalysis and solar water splitting. However, Cu 2 O is not intrinsically stable under illumination in aqueous solutions, and the edge of the valence band is not positive enough to provide sufficient overpotential for water oxidation. The stability and band edge position of nanostructured materials depend on crystallite size. In this paper, we describe a new strategy to vary the size of Cu 2 O nanoparticles using mesoporous silica supports. First, CuO nanoparticles were obtained via impregnation-drying-heating. The size of the nanoparticles was tuned by varying either the concentration of Cu precursor or the pore diameter of the supporting silica. Subsequently, the CuO was converted to Cu 2 O without particle growth by gas-phase reduction with carbon monoxide. The visible light absorption of these nanoparticles depended on the copper oxide phase and crystallite size, leading to a direct band gap energy of 2.60 eV for 2 nm Cu 2 O nanoparticles compared to 1.94 eV for macrocrystalline Cu 2 O. Our results highlight a new synthesis strategy for the preparation of metal-oxide nanoparticles with controlled sizes of 2–15 nm that are not directly accessible by alternative synthesis techniques. The as-obtained 15 nm Cu 2 O nanoparticles were used for H 2 evolution in a water-methanol mixture, the photocatalyst gave a H 2 evolution rate of 11.5 × 10 −3 μmol min −1 which corresponded to an internal quantum efficiency of 15.8% and an overall quantum efficiency of 3.5% for light between 310 and 710 nm. Finally, the nanoparticles were stable during three hours of light illumination. [ABSTRACT FROM AUTHOR]

• The recent advances of graphitic carbon nitride for the hydrogen production and photocatalytic water splitting were summarized. • The drawbacks and the solution to overcome it have been discussed. • The advanced strategies to increase the performance of graphitic carbon nitride have been systematically discussed. The future energy crisis and environmental degradation can only mitigate by harvesting solar energy into renewable, safe, economical and clean technology like water splitting. The graphitic carbon nitride has an attractive band structure, good chemical stability, earth-abundant and significantly easily fabricated which makes an application for the generation of hydrogen by water splitting. In this paper, we try to critically focus on the current progress and future development of the different strategies of water splitting using graphitic carbon nitride (g-C 3 N 4) for hydrogen generation. In this context, we discuss recent strategies like metal and non-metal doping (electronic structure), morphology tuning (geometric structuring), use of mediators (Z-scheme technology), defects engineering, plasmonic materials, dye-sensitization, perovskite oxides, carbon nitrides, carbon dots, metal organic framework, and a bimetallic cocatalyst. Finally, we summarize the recent advances and future developments of g-C 3 N 4 bases photocatalysis. [ABSTRACT FROM AUTHOR]

Nano-fibrillated cellulose (NFC), an abundant renewable bio-macromolecule, has received much attention in the research community. The study detailed herein is related to the preparation of photocatalytic nanocomposites consisting of nano-fibrillated cellulose/magnetite/titanium dioxide nanoparticles (NFC@Fe 3 O 4 @TNP). The aim of this study is to improve the photocatalytic efficiency of NFC-TNP composites and to improve their recyclability during the photocatalytic hydrogen generation. The NFC@Fe 3 O 4 @TNP nanocomposites were characterized by TEM, EDX, SAED, XRD, XPS, FTIR, Raman spectra and VSM techniques. The results showed that Fe 3 O 4 NP and TNP were well-distributed on the surface of NFC. The photocatalytic efficiency study showed that NFC@Fe 3 O 4 @TNP nanocomposites represented a higher photocatalytic hydrogen generation rate in comparison with that of NFC-TNP sample. In addition, the NFC@Fe 3 O 4 @TNP nanocomposites can be readily recovered from the system using a magnet due to their stable superparamagnetic properties, and they had only a marginal loss of TNP and photocatalytic efficiency after fifteen cycles. [ABSTRACT FROM AUTHOR]