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2 D transition metal dichalcogenide materials with layered nanostructures and specific phases usually exhibit excellent catalytic activities for the hydrogen evolution reaction (HER). A facile solvothermal process was used to prepare ultrathin noble‐metal‐free 2 D biphasic MoSe2 nanosheets composed of a metastable metallic 1T phase and a semiconducting 2H phase. High metallic 1T phase content and few‐layer‐thick MoSe2 nanosheets were obtained by tuning the amount of NaBH4 used in the reaction. The optimal integration of a metallic 1T phase and an environmentally stable 2H phase in MoSe2 electrocatalysts provides abundant active sites and good conductivity beneficial for the HER. The combination of experimental results and DFT calculations implies that the electrocatalytic activity for the HER on the MoSe2 surface goes through a collaborative Heyrovsky and Volmer reaction process. The theoretical studies suggest that the presence of 1T‐MoSe2 could reduce the band energy relative to 2H‐MoSe2 and, consequently, accelerate the sluggish HER kinetics of 2H‐MoSe2. This work provides valuable and novel insights into the understanding of the structure–activity relationships in 2 D transition metal dichalcogenide electrocatalysts. [ABSTRACT FROM AUTHOR]

Currently, promoting solar absorption ability and photoexcited charge separation and transfer of semiconductors is of significance for enhancing their solar-to-hydrogen (STH) efficiency. Hollow-structured design and element doping strategy have proven to be effective in strengthening solar absorption and manipulating the charge dynamics. Herein, an ingenious design of doping phosphors (P) into hollow-structured CdS octahedrons is applied for achieving effective photocatalytic hydrogen production. The P-doped CdS semiconductor has a hollow interior for enhancing the photon absorbance and a narrow bandgap with upshift of valence band for facilitating photoinduced charge separation and transport, all of which contribute to their improved photocatalytic performance. Consequently, the synergistic effect in the designed archicture leads to an enhanced hydrogen production rate of up to 9.58 mmol·g−1 h−1, being about 11.7 fold higher than the reported CdS nanorods. Our work offers a new way for developing other types of sulfur-based semiconductors towards effective solar-to-hydrogen conversion. [Display omitted] • Phosphors-doped CdS hollow octahedrons have been successfully synthesized. • P-doped CdS exhibits an enhanced photocatalytic hydrogen production rate. • It is attributed to synergy effect of structural design and dopant strategy. • The present approach gives a reference to design advanced semiconductors. [ABSTRACT FROM AUTHOR]

β-SiC is a suitable photocatalyst for hydrogen evolution reaction because of its proper band structure (2.36 eV) and high chemical stability. Porousβ-SiC has a large surface area that can increase the number of reactive sites and shorten the charge transport pathways between the material interior and surface, thereby significantly improving the hydrogen evolution reaction performance. In the present study, hierarchical macroporousβ-SiC monolith composed of nanocrystals was directly prepared using SiO2opal as both template and precursor via the magnesiothermic reduction method at 750 °C. An interfacial magnesiothermic reaction model was presented as well. Theβ-SiC sample exhibited high photoelectric conversion performance and stability as a catalyst for hydrogen evolution. [ABSTRACT FROM AUTHOR]

Transition metal sulfides are cheap and efficient catalysts for water splitting to produce hydrogen; these compounds have attracted wide attention. Nickel sulfide (NiS2) has been studied in depth because of its simple preparation process, excellent performance and good stability. Here, we propose a modification to the hydrothermal synthesis method for the fabrication of a highly efficient and stable NiS2 electrocatalyst prepared by two different sulfur sources, i.e., sulfur powder and C3H7NaO3S2 (MPS), for application in hydrogen evolution reactions. The obtained NiS2 demonstrated excellent HER performance with an overpotential of 131 mV to drive -10 mA cm−1 in 0.5 M H2SO4 solution with 5mV performance change after 1000 cycles of stability testing. We believe that this discovery will promote the industrial development of nonprecious metal catalysts. [ABSTRACT FROM AUTHOR]

Biosensors are widely used in production and life, and can be used in medicine, industrial production, and scientific research. Among them, the detection of pH has always received extensive attention. In this study, we demonstrate the use of a one-step hydrothermal method to prepare Co-FeS2/CoS2 nanomaterials as pH sensor (pH vs. overpotential) for the first time. The proposed pH sensor exhibits outstanding performance in KOH solutions via electrochemical methods with good stability. Overall, the results of this study not only add to the non-noble transition metal electrocatalysis research, but also identify important sensing characteristics for electrocatalysts. [ABSTRACT FROM AUTHOR]

A Janus Co nanoparticles and Mo 2 C heterostructures decorated N-Doped carbon for efficient overall water splitting. • A Janus Co nanoparticles and Mo 2 C decorated N-Doped hierarchical nanocarbon. • In-situ synthesis of heterostructures containing bifunctional active sites. • The Co and MO 2 C coupled N-doped carbon hybrid structure possess superior HER, OER and overall water splitting performance. The fabrication of high-performance and stable electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of importance for sustainable water-splitting technologies. Herein, the cobalt (Co) nanoparticles and molybdenum carbide (Mo 2 C) heterostructures anchored N-doped carbon (Co/Mo 2 C@NC-800) was designed as bifunctional electrocatalyst for overall water splitting via a simple pyrolysis approach for metal organic frameworks (MOFs) precursor. This composite shows a remarkable performance for HER and OER with a small overpotential of 121 mV and 311 mV at 10 mA cm−2, respectively. When the optimized electrocatalyst was employed as both anode and cathode for overall water splitting in a two-electrode system, the electrolyzer achieves a low cell voltage of 1.67 V at 10 mA cm−2 in 1 M KOH, as well as a superior and stable long-time operation of 30 h. The promising hybrid material demonstrates excellent electrocatalysis performance due to effective combination of the best of both worlds: Mo 2 C with remarkable HER performance and Co nanoparticles with excellent OER activity. The Mo 2 C possesses strong hydrogen binding energy and Co exhibits prominent electrical conductivity, thus the construction of heterostructures achieves more active sites with different functions and significantly boosts HER and OER process. The novel and effective synthesis strategy provides new insights into the design of outstanding non-noble metal bifunctional electrocatalysts for overall water splitting. [ABSTRACT FROM AUTHOR]

• A composite photocatalyst of Ag 3 PO 4 particles decorated on modified crispy g-C 3 N 4 flake was fabricated. • Photocatalytic oxygen evolution over Z-scheme heterojunction is roughly 7-fold higher than that in Ag 3 PO 4. • Highly efficient oxygen-evolving performance is mainly attributed to accelerated interfacial charge transfer. • Surface modification and nitrogen atmosphere favor well-organized g-C 3 N 4 nanostructures and enhanced photocatalytic activity. Searching for highly efficient photocatalysts for water oxidation is the footstone for the development of overall water splitting systems and has been actively pursued. The construction of artificial Z-scheme heterojunction photocatalysts has been conclusively proven to be effective in boosting charge transport property and in improving the OER performance. Herein, Ag 3 PO 4 particles anchored on modified crispy g-C 3 N 4 flakes have been successfully fabricated. KOH-assisted surface modification of g-C 3 N 4 flakes and intimate interfacial contact favor the accelerated charge transfer and highly improved OER efficiency. Ultrafast spectroscopy results reveal that modified g-C 3 N 4 with crispy nanostructures possesses more trap-induced long-lived photogenerated holes, which are extremely helpful to combine with photo-generated electrons from the conduction band (CB) position of Ag 3 PO 4 via the specific Z-scheme configuration, leaving more holes in the valence band (VB) of Ag 3 PO 4 for the enhanced OER. Superb oxygen-evolving performance highlight the great promise of Z-scheme Ag 3 PO 4 -based heterojunctions in solar-driven photocatalytic water splitting. [ABSTRACT FROM AUTHOR]

• 1D CdS/2D Ti3C2 MXene Schottky heterojunction was successfully fabricated. • In situ constructed Schottky photocatalyst exhibits enhanced HER performance. • Ultrathin 2D MXene enhances light absorption and accelerates charge transport. • The specific Schottky interface is responsible for the improved HER activity. Benefiting from excellent metallic conductivity, full-spectrum solar energy absorption and rich active sites on the surface, atomically thin two-dimensional transition metal carbide (2D MXene) shows great promise in improving solar-to-hydrogen efficiency and has drawn intense interest in the field of photocatalysis. However, controllable construction of ultrathin 2D MXene-based heterojunction photocatalysts still remains a significant challenge. Herein, one-dimensional (1D) CdS nanorod/2D MXene nanosheet heterojunctions with well-defined nanostructures and strong interfacial coupling are fabricated by in situ assembling solvothermally-generated CdS nanorods on ultrathin Ti 3 C 2 MXene nanosheets. Due to their specific interface characteristics, 1D/2D Schottky heterojunction is capable of providing accelerated charge separation and a lower Schottky barrier for solar-driven hydrogen evolution from water splitting. As expected, the Schottky-based photocatalyst is 7-fold more active in the illuminated hydrogen evolution reaction (HER) than pristine CdS nanorods, implying the synergistic effects between n-type semiconductor CdS and highly conductive 2D Ti 3 C 2 MXene nanosheets. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C 3 N 4) is sprouted as an efficient and cost-effective visible-light-responsive photocatalyst for yielding hydrogen from water splitting. However, a brisk recombination of light-induced electron-hole (e− - h+) pairs in the bulk g-C 3 N 4 effectuate poor quantum efficiency in the hydrogen evolution reaction (HER). The shuttle redox mediator manifests ample potential in accelerating photo-induced carrier segregation and in boosting charge transport in the HER. Here, we report that exploiting Ag/Ag(I) and Fe(III)/Fe(II) shuttle redox mediators, the hydrogen-evolving rate of the aforementioned g-C 3 N 4 nanosheets can reach 3213.3 μmol g−1 h−1 under visible-light irradiation, which is eight times higher than that of pure g-C 3 N 4 (404.82 μmol g−1 h−1). The effective coupling between a hydrogen-evolving catalyst and appropriate shuttle redox mediators significantly improves the HER-photocatalytic performance of native g-C 3 N 4 nanosheets. Density functional theory calculations show that the presence of Ag/Ag(I) and Fe(III)/Fe(II) shuttle redox mediators can effectively promote H atom adsorption and facilitate a H 2 O reduction reaction. This work envisages a new and deft approach for contriving high-performance g–C 3 N 4 –based photocatalysts for highly efficient solar-to-fuel conversion. • Ag/Ag(I) and Fe(III)/Fe(II) shuttle redox were loaded on the surface of g-C 3 N 4. • The modified g-C 3 N 4 showed excellent photocatalytic H 2 activity and chemical stability. • Double shuttle redox on the g-C 3 N 4 boost the separation of photoexcited charges. [ABSTRACT FROM AUTHOR]

• 2D g-C 3 N 4 nanosheet was fabricated by the supramolecular assembly approach. • Assembled 2D g-C 3 N 4 photocatalyst demonstrates enhanced HER performance. • 2D nanostructure accelerates charge transport and solar-to-hydrogen efficiency. • Ultrafast spectroscopy reveals charge carrier dynamics in 2D g-C 3 N 4 nanosheets. Two-dimensional graphitic carbon nitride (2D g-C 3 N 4) nanostructures have been the focus of substantial research interest recently owing to their promising photoactive properties for use in solar-to-fuel conversion. However, the synthesis of 2D g-C 3 N 4 nanomaterials remains a significant challenge. Here we successfully synthesized 2D g-C 3 N 4 nanosheets via a supramolecular chemistry approach. 2D g-C 3 N 4 nanostructures not only enhance the visible light-harvesting property but also provide more catalytic sites for improved hydrogen evolution reaction (HER). More importantly, we describe experimental findings concerning the dynamics of charge and energy transfer by using ultrafast spectroscopy in combination with in-situ electron spin resonance (ESR) characterization. The mechanistic investigation reveals that the introduction of a benzene-substituted melamine motif can remarkably accelerate the electron-hole separation and suppress the recombination of photogenerated charge carriers. The carrier separation dynamics is expected to be tailored by engineering the surface and morphology of g-C 3 N 4 , which favors enhanced solar photocatalytic HER efficiency. [ABSTRACT FROM AUTHOR]