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It has been rarely reported the morphological control of derivatives of metal‐organic frameworks (MOFs) in hydrothermal conditions for photocatalytic applications. We report here a family of highly efficient composite photocatalysts composed of terephthalic acid/terephthalate (TPA) ligand and TiO2 with various morphologies (e. g. nanoparticles, nanosheets, and nanorods). The composites are synthesized by a simple one‐step hydrothermal method in various solvents (i. e. H2O, HF, H2SO4, HCl, and HNO3) using Ti‐based MOF (MIL‐125(Ti)) as precursor. The formation mechanism of composite materials with different morphological features is discussed. Impressively, the composite of TiO2 nanoparticles/TPA synthesized using H2O as solvent under hydrothermal condition exhibits the highest photocatalytic H2 activity among the studied materials, with a photocatalytic H2 production rate of 6.38 mmol g−1 h−1, which is approximately 7.5‐fold higher than pure TiO2 (Degussa, P25) and prominent apparent quantum efficiency (AQE) of 65 % at 365 nm. Furthermore, the mechanism of boosted photocatalytic H2 production is discussed. [ABSTRACT FROM AUTHOR]

The development of alkaline polymer electrolyte fuel cells and alkaline water electrolysis requires nonprecious metal catalysts for the hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER). Herein, it is reported a phase‐separated Mo–Ni alloy (PS‐MoNi) that is composed of Mo metal and embedded Ni metal nanoparticles. The PS‐MoNi shows excellent hydrogen electrode activity with a high exchange current density (−4.883 mA cm−2), which is comparable to the reported highest value for non‐noble catalysts. Moreover, the amorphous phase‐separated Mo–Ni alloy has better structural and electrochemical stability than the intermetallic compound Mo–Ni alloy (IC‐MoNi). The breakdown potential of PS‐MoNi is as high as 0.32 V, which is much higher than that of reported IC‐MoNi. The X‐ray absorption near edge structure (XANES) and density functional theory (DFT) calculations indicate the electrons transfer from Mo to Ni for PS‐MoNi, leading to suitable adsorption free energies of H* (ΔGH*) on the surface of Mo. This means that the electron density modulation of Mo metal by embedded Ni metal nanoparticles can produce excellent HOR and HER performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • [Mo 3 S 13 ]2− nanoclusters are highly dispersed into the micropores of TpPa-1-COF. • The size and micro-environment of micropores play a central role in anchoring MS-c. • The photocatalytic H 2 evolution rate of MS-c@TpPa-1 is increased by 4.7 times. • The coordinated Mo − N groups between MS-c and TpPa-1-COF result in enhanced stability. • The favorable electron–proton transfer to form H* occurs on the S instead of N sites. Non-noble-metal-based [Mo 3 S 13 ]2− nanoclusters (MS-c) as a co-catalyst face the problems of instability and inevitable aggregation, which limit its photocatalytic applications. Herein, β-ketoenamine-linked covalent organic framework (COF), namely TpPa-1-COF, was utilized to embed MS-c. The micropores of TpPa-1-COF could not only limit the growth of MS-c to achieve its high dispersion but also play a central role in anchoring MS-c. Moreover, the structural stability of MS-c is highly enhanced due to the confinement effect of TpPa-1-COF, and the visible-light-driven photocatalytic H 2 evolution rate of 528 μmol g−1h−1 for MS-c@TpPa-1 (0.3: 1), which is increased by 4.7 times as compared with that of TpPa-1-COF. The density functional theory (DFT) calculations indicate that the electrons transfer from TpPa-1 to MS-c occurs at the interface of MS-c@TpPa-1 in the ground state based on the charge density difference analysis. With the irradiation of visible light, the photoexcited electrons derived from the π-conjugated TpPa-1-COF backbone could be delivered to the embedding MS-c through the coordinated Mo − N groups, and the favorable electron–proton transfer to form H* and efficient desorption of H 2 occurs on the S sites instead of N sites in MS-c@TpPa-1, resulting in the enhanced photocatalytic H 2 evolution rate. Overall, this work provides a novel approach for embedding the unstable MS-c with low cost into the micropores of COF via coordination bonds to improve the structural stability and photocatalytic activity. [ABSTRACT FROM AUTHOR]

It is still challenging to fabricate photocatalysts via loaded metal cocatalysts with good dispersion onto the conjugated polymers (CPs). Herein, a donor-acceptor (D–A) structural CP of PyDTDO-3 was employed to host platinum (Pt) nanoparticles (NPs) using N , N ′-dimethylformamide (DMF) as a protectant, stabilizer, and reducing agent, which not only promotes Pt NPs to have excellent dispersion property on the surface of PyDTDO-3 but also endows Pt NPs to maintain metallic Pt0 species. As a result, the PyDTDO-3 loaded with Pt NPs exhibits remarkable hydrogen (H 2) evolution activity with a rate of 39.9 mmol g−1 h−1 under visible light irradiation, and the fair stability of optimal 7% Pt/PyDTDO-3 is expressed in the rate of H 2 generation upon 30 h cycling. Based on density functional theory (DFT) calculations, it has been demonstrated that Pt NPs are selectively loaded onto the acceptor (A) unit of PyDTDO-3 that has the lowest adsorption energies (E ads) and the closest bond lengths between the Pt NPs and PyDTDO-3. Moreover, there are much more electrons filling at the Fermi level (E f), indicating the optimal 7% Pt/PyDTDO-3 with high electroconductivity timely captured and removed the photoinduced electrons and thus realized the space separation efficiency of electron-hole pairs. Overall, our findings offer a rational way to load metal cocatalysts onto CPs with good dispersion for efficient photocatalytic H 2 evolution. [Display omitted] • Well-dispersed Pt NPs are fabricated onto the conjugated D-A type polymers. • DMF was used as a protectant, stabilizer, and reducing agent to obtain metallic Pt0. • Pt (111) plane is selectively loaded onto the acceptor (A) unit of PyDTDO-3. • The photoinduced electrons transfer from D to A unit of PyDTDO-3 and then to Pt NPs. • The optimal 7% Pt/PyDTDO-3 exhibits photocatalytic H 2 rate of 39.9 mmol g−1 h−1. [ABSTRACT FROM AUTHOR]

Benefiting from Ni can provide excellent hydrogen adsorption free energy and tungsten has ideal hydroxide adsorption free energy, the designed Janus Ni/W bimetallic materials can provide remarkable HER/HOR activity. [Display omitted] The development of hydrogen energy is limited by the high cost of platinum group metals (PGM). There is an urgent need to design efficient PGM-free electrocatalysts in the hydrogen electrode. Herein, Janus Ni/W bimetallic materials are proposed as an effective PGM-free bifunctional hydrogen electrocatalyst. By constructing the bimetallic materials, a synergistic effect is realized to enhance the reaction kinetics and improve the catalytic performance. In general, Ni can provide excellent H ad sites, and W serves as OH ad sites. Therefore, the synergistic effect of Ni and W can improve the kinetics of hydrogen evolution reaction and the hydroxide oxidation reaction. Ni/W@NF can obtain the hydrogen evolution reaction current density of 10 mA cm−2 with an overpotential of only 62.6 mV, and the exchange current density of hydroxide oxidation reaction can reach 1.83 mA cm−2. This work provides a new idea for the design of high-efficiency and low-cost PGM-free bifunctional hydrogen electrocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • An Z-scheme heterojunction has been successfully developed. • CPDs/ZIS heterostructure improves the light capture and charges life. • The CPDs highly promotes the photocatalytic hydrogen evolution of ZIS. • DFT calculations indicated a decrease in the H* adsorption's free energy. To effectively separate electron-hole pairs produced by light, a heterojunction arrangement can be employed, thereby improving photocatalytic efficiency. In this study, a simple hydrothermal process is used to manufacture carbonized polymer dots/ZnIn 2 S 4 (CPDs/ZIS) heterostructure, which enhances the light absorption and charge carrier lifetime in comparison to bare ZnIn 2 S 4 (ZIS). Upon irradiation with visible light, the 3-CPDs/ZIS composite generates hydrogen at a rate of 133 μmol g−1 h−1, which is 8.9 times faster than that of pure ZIS. The addition of CPDs can increase the range of light that can be absorbed, extend the service life of the optical charge, increase the specific surface area, and promote charge separation and transmission, which could effectively accelerate the photocatalytic reduction reaction. The presence of CPDs results in the introduction of multiple transition energy states and a decrease in the H* adsorption free energy, which enhances the hydrogen evolution activity according to the theoretical calculation findings of density functional theory (DFT) and Gibbs free energy of the hydrogen evolution process. Combining theoretical calculations and experimental results, a direct Z-type heterojunction mechanism is proposed for the hydrogen evolution promotion effectiveness of CPDs/ZIS under visible light. [ABSTRACT FROM AUTHOR]

[Display omitted] • An entirely novel kind of GQDs-modified TpPa-1-COF photocatalyst was prepared. • GQDs were synchronously deposited onto the TpPa-1-COF by the in-situ method. • GQDs serve as a photosensitizer that enhances the optical absorption ability. • The 0.44% GQDs/TpPa-1-COF shows a better H 2 production than bare COF by 2.9 times. • DFT simulation indicates the highly efficient interfacial charge migration. The photocatalytic activity of covalent organic frameworks (COFs) to evolve hydrogen (H 2) triggered by visible light has been promising, but the separation and migration efficiency of photogenerated electron-hole pairs still have to be improved. In the study, we designed and synthesized a kind of graphene quantum dots (GQDs) modified β-ketoenamine-linked COF composite (GQDs/COF) by an in-situ method to improve its photocatalytic H 2 evolution for the first time. The resulting 0.44% GQDs/TpPa-1-COF shows a rate of H 2 production of 487 μmol g−1h−1 with the illumination of visible light, outperforming those of bare TpPa-1-COF by 2.9 times. It is found that the GQDs serve as a photosensitizer that effectively enhances the optical absorption ability. Moreover, GQDs serve as a means of collecting photoinduced electrons as for preventing the subsequent recombination of carriers excited by visible light. Furthermore, the Ohmic contact effect between the TpPa-1-COF and GQDs facilitates the highly efficient migration of photoinduced electrons, which has been demonstrated by the density functional theory (DFT) calculation results. Overall, this work provides a novel strategy to design COF-based composites and gives some insight into the role of GQDs on enhanced photocatalytic activity. [ABSTRACT FROM AUTHOR]

Hydrogen is considered as an efficient energy alternative, and the use of offshore wind power to electrolyze seawater to produce hydrogen will become the future model. Here, nickel-doped tungsten oxide is proposed to realize hydrogen production from seawater. Ni-WO x @NF was prepared experimentally, in which Ni was doped into WO x to replace part of the W sites. There is a volcanic relationship between the amount of Ni doping and the activity of the hydrogen evolution reaction. Particularly in alkaline seawater, Ni-WO x @NF only needs an overpotential of 45.69 mV to reach a current density of 10 mA cm−2 and exhibits stability over 120 h. In addition, theoretical calculations confirmed that Ni doping can optimize the activity of hydrogen evolution reaction. This work proposes that nickel doping can enhance the hydrogen evolution reaction activity of tungsten oxide with excellent corrosion resistance, enabling it to work efficiently and stably in alkaline seawater. [Display omitted] • Nickel enters the lattice of tungsten oxide in the form of substitutional doping. • Nickel doping optimizes the adsorption free energy of tungsten oxide. • Ni-WO x @NF exhibits excellent activity and stability in alkaline seawater. • There was a volcanic relationship between nickel doping and catalytic activity. • This strategy can guide the design of alkaline seawater hydrogen evolution catalyst. [ABSTRACT FROM AUTHOR]