Electrocatalysis induced reconstruction of RuNiPO for highly efficient hydrogen evolution reaction

Reconstruction during the catalytic process has been considered to play a key role for the performance.Here we report a RuNiPO based catalyst for efficient alkaline hydrogen evolution reaction(HER),which can benefit from a long-term reconstruction during HER for 10 h to continuously increase the performance.The final catalyst(e-RuNiPO)shows a huge morphology change from bulk sphere to highly exposed layered structure in the electrocatalysis process,and exhibits an interesting electronic structure modification with the electron transfer from Ru to Ni for better interfacial interaction and quick charge transfer.Due to the favorable morphology with more exposed active sites and the optimized electronic structure,the final catalyst can achieve an outstanding performance with only an overpotential of 15 mV at 10 mA cm^(-2)(with a good stability more than 100 h),even outperforming the performance of benchmark 20 wt%Pt/C catalyst(18 mV at 10 mA cm^(-2))by using a much lower Ru content.

Unraveling the role of Ti3C2 MXene underlayer for enhanced photoelectrochemical water oxidation of hematite photoanodes

Hematite is regarded as a promising photoanode for photoelectrochemical(PEC) water splitting.However,the charge recombination occurred at the interface of FTO/hematite strictly limits the PEC performance of hematite.Herein,we reported a Ti3C2 MXene underlayer modified hematite(Ti-Fe2O3) photoanode via a simple drop-casting followed by hydrothermal and annealing processes.Owing to the bifunctional role of Ti3C2 MXene underlayer in improving the interfacial properties of FTO/hematite and providing Ti source for the construction of Fe2 TiO5/Fe2O3 heterostructure in hematite nanostructure,the bulk and interfacial charge transfer dynamics of hematite are significantly enhanced,and consequently enhancing the PEC performance.Compared with the pristine hematite,the as-prepared Ti-Fe2O3 photoanode shows an increased photocurrent density from 0.80 mA/cm^(2) to 1.30 mA/cm^(2) at 1.23 V vs.RHE.Moreover,a further promoted PEC performance including a dramatically increased photocurrent density of 2.49 mA/cm^(2) at1.23 V vs.RHE and an obviously lowered onset potential is achieved for the Ti-Fe2O3 sample after the subsequent surface F-treatment and the loading of FeNiOOH cocatalyst.Such results suggest that the introduction of Ti3C2 MXene underlayer is a facile but effective approach to improve the PEC water splitting activity of hematite.

Carbon nanotube supported PtOx nanoparticles with hybrid chemical states for efficient hydrogen evolution

Efficient electrocatalysts for hydrogen evolution reaction(HER) in alkaline solution are highly required for water splitting.Here we design an ultra-small PtOx nanoparticle with hybrid Pt chemical states on carbon nanotubes as highly efficient alkaline HER catalyst,which shows a low overpotential of 19.4 mV at 10 mA cm^(-2),a high mass activity of 5.56 A mg_(Pt)^(-1) at 0.1 V, and a stable durability for at least 20 h.The HER performance is better than that of the benchmark 20 wt% Pt/C while the Pt content in the catalyst is only about one tenth of that in Pt/C.It also represents one of the best catalysts ever reported for HER in alkaline solution.Synchrotron radiation X-ray absorption spectroscopy reveals that the efficient and stable alkaline HER performance can be attributed to the favorable design of hybrid chemical states of Pt with carbon nanotubes,which exhibits abundant surface Pt-O as active catalytic sites and forms stable Pt-C interfacial interaction to both anchor the NPs and improve the synergistic effect between catalyst and substrate.

Cobalt coordination with pyridines in sulfurized polyacrylonitrile cathodes to form conductive pathways and catalytic M-N4S sites for accelerated Li-S kinetics

Sulfurized polyacrylonitrile(SPAN)represents a unique class of cathode material for lithium sulfur(Li-S)batteries as it eradicates the polysulfides shuttling issue in carbonate-based electrolyte.However,due to the essential chemical S-linking and organic nature of SPAN,the active mass percentage and rate capability are two bottleneck issues preventing its ultimate deployment outside of laboratories.In the current work,aiming to endow both the charge conductivity and catalytic activity to SPAN for maximizing the redox kinetics of S conversion,a freestanding nanofibrous SPAN cathode embedding conductive CNTs and atomically dispersed Co centers is fabricated via multivariate electrospinning.While the CNTs enable dramatically enhancing the fiber conductivity and generating mesoscopic porosity for facilitating charge and mass transportation,the cross-linking of SPAN by Co-N_(4) S motifs creates extra charge conduction pathways and further serves as the catalytic active sites for expediting redox S conversion.As a result,an extraordinary Li-SPAN performance is achieved with a high specific capacity up to 1856 mAh g^(-1)@0.2 C,a superb rate capability up to 10 C,and an ultra-long battery life up to 1500 cycles@1 C.Consequently,our study here provides insights into the adoption of coordination chemistry to maximize the sulfur utilization by ensuring a more complete redox conversion from SPAN to Li2 S,and vice versa.

FeF_(x) and Fe_(2)ZrO_(5) Co-modified hematite for highly efficient solar water splitting

Hematite is an excellent catalyst for photoelectrochemical (PEC) water splitting but its performance has been highly limited by poor conductivity and high charge recombination.Here by a Zr-based treatment to create bulk Fe_(2)ZrO_(5) in hematite and a F-based treatment to form an ultrathin surface FeF_(x) layer,the charge transfer can be highly improved and the charge recombination can be significantly suppressed.As a result,the FeF_(x) /Zr-Fe_(2)O_(3) photoanode presents an enhanced PEC performance with a photocurrent density of 2.43 m A/cm^(2)at 1.23 V vs.RHE,which is around 3 times higher than that of the pristine Fe_(2)O_(3) .The FeF_(x) /Zr-Fe_(2)O_(3) photoanode also shows a low onset potential of 0.77 V vs.RHE (100 mV lower than the pristine hematite).The performance is much higher than that of the sample treated by Zr or F alone,suggesting the synergistic effect between bulk Fe_(2)ZrO_(5) and surface FeF_(x) .By coupling with the FeNiOOH co-catalyst,the final photoanode can achieve a high photocurrent density of 2.81 mA/cm^(2) at 1.23 V vs.RHE.The novel design of Zr and F co-modified hematite can be used as a promising way to prepare efficient catalysts for solar water splitting.

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~à.A maximum turnover frequency(TOF)of 50.3 mol_(H2)mol^(à1)_(total metal)min^(à1)(135.6 mol_(H2)mol_(Cu)^(à1)min^(à1))was achieved at ambient temperature,which is superior to those of previously reported Fe or Cu based systems.

Soft X-Ray Absorption Spectroscopy of Advanced Two-Dimensional Photo/Electrocatalysts for Water Splitting

Photo/electrocatalytic water splitting has been considered as one of the most promising approaches for the clean hydrogen production. Among various photo/electrocatalysts,2D nanomaterials exhibit great potential because of their conspicuous properties. Meanwhile,synchrotron-based soft X-ray absorption spectroscopy(XAS) as a powerful and element-specific technique has been widely used to explore the electronic structure of 2D photo/electrocatalysts to comprehensively understand their working mechanism for the development of high-performance catalysts. In this work, the recent developments of soft XAS techniques applied in 2D photo/electrocatalysts have been reviewed, mainly focusing on identifying the surface active sites,elucidating the location of heteroatoms, and unraveling the interfacial interaction in the composite.The challenges and outlook in this research field have also been emphasized. The present review provides an in-depth understanding on how soft XAS techniques unravel the correlations between structure and performance in 2D photo/electrocatalysts, which could guide the rational design of highly efficient catalysts for photo/electrocatalytic water splitting.

Highly efficient metal-free catalyst from cellulose for hydrogen peroxide photoproduction instructed by machine learning and transient photovoltage technology

Great attention has been paid to green procedures and technologies for the design of environmental catalytic systems.Biomassderived catalysts represent one of the greener alternatives for green catalysis.Photocatalytic production of hydrogen peroxide(H_(2)O_(2))from O_(2) and H_(2)O is an ideal green way and has attracted widespread attention.Here,we show a metal-free photocatalyst from cellulose,which has a high photocatalytic activity for the photoproduction of H_(2)O_(2) with the reaction rate up to 2,093μmol/(h·g)and the apparent quantum efficiency of 2.33%.Importantly,a machine learning model was constructed to guide the synthesis of this metal-free photocatalyst.With the help of transient photovoltage(TPV)tests,we optimized their fabrication and catalytic activity,and clearly showed that the formation of carbon dots(CDs)facilitates the generation,separation,and transfer of photo-induced charges on the catalyst surface.This work provides a green way for the highly efficient metal-free photocatalyst design and study from biomass materials with the machine learning and TPV technology.

Ascorbic acid derived carbon dots promote circadian rhythm and contribute to attention deficit hyperactivity disorder

Attention deficit hyperactivity disorder(ADHD)is one of the most prevalent psychiatric disorders in children,and ADHD patients always display circadian abnormalities.While,the ADHD drugs currently used in clinic have strong side effects,such as psychosis,allergic reactions,and heart problems.Here,we demonstrated carbon dots derived from the ascorbic acid(VCDs)could strongly rescue the hyperactive and impulsive behaviour of a zebrafish ADHD disease model caused by per1b mutation.VCDs prolonged the circadian period of zebrafish for more than half an hour.In addition,the amplitude and circadian phase were also changed.The dopamine level was specifically increased,which may be caused by stimulation of the dopaminergic neuron development in the midbrain.Notably,it was found that the serotonin level was not altered by VCDs treatments.Also,the gene transcriptome effects of VCDs were discussed in present work.Our results provided the dynamic interactions of carbon dots with circadian system and dopamine signaling pathway,which illustrates a potential application of degradable and bio-safe VCDs for the treatment of the attention deficient and hyperactive disorder through circadian intervention.

Layered double hydroxide nanosheets activate CsPbBr_(3) nanocrystals for enhanced photocatalytic CO_(2) reduction

Halide perovskite nanocrystals are potential catalysts for CO_(2) photoreduction,while,the strong radiative recombination and insufficient stability limit their catalytic performance and application.Herein,we report that layered double hydroxide nanosheets activate CsPbBr_(3) nanocrystals(CLDH)for enhanced photocatalytic CO_(2) reduction.These CLDH heterojunctions show the remarkably enhanced CO_(2) photoreduction performance;without cocatalyst and sacrificial agent,the average electron consumption rate of CLDH(49.16μmol·g^(−1)·h^(−1))is approximately 3.7 times higher than that of pristine CsPbBr_(3).Also,CLDH catalyst exhibits a robust stability after ten cycles over 30 h.

Vertical 3D Printed Pd/TiO_(2) Arrays for High Efficiency Photo-assisted Catalytic Water Treatment

Catalytic degradation of organic contaminants is at the frontier of water treatment due to its selectivity,energy savings,and ability to convert harmful contaminants into harmless or even valuable chemical products for recycling.However,achieving sufficiently high performance in the catalytic removal of organic contaminants for practical application is still extremely challenging.Herein,we report a Pd-decorated TiO_(2)(Pd/TiO_(2))hierarchical vertical array for fast and efficient catalytic water treatment.Such a forest-like Pd/TiO_(2) vertical array demonstrates the following distinct advantages over conventional planar or bulk catalytic systems:1)abundant anchoring sites for nanocrystals loading;2)high sunlight absorption;3)efficient mass transfer channels for the reactants and products.As a proof of concept,the Pd/TiO_(2) array demonstrated rapid and efficient photo-assisted catalytic reduction of high concentrations of 4-nitrophenol wastewater(2 g/L,ca.14.38 mmol/L)and its feasibility for continuous flow wastewater treatment.The turnover frequency(TOF)value of the Pd/TiO_(2) array was up to 8.00 min^(-1),which was approximately 4.2 times that of planar Pd/TiO_(2) film with the same area(1.91 min^(-1)).Our strategy of incorporating nanocatalysts with a hierarchical vertical array provides a promising approach to boosting the catalytic performance of catalysts for different chemical reactions.

A photoactive process cascaded electrocatalysis for enhanced methanol oxidation over Pt-MXene-TiO2 composite

Highly efficient photo-assisted electrocatalysis for methanol oxidation reaction(MOR)realizes the conversion of solar and chemical energy into electric energy simultaneously.Here we report a Pt-MXene-TiO2 composite for highly efficient MOR via a photoactive cascaded electro-catalytic process.With light(UV and visible light)irradiation,MXene-TiO2 serves as the photo active centre(photoinduced hole)to activate the methanol molecules,while Pt particles are the active centre for the following electro-catalytic oxidation of those activated methanol molecules.Pt-MXene-TiO2 catalyst exhibits a lower onset potential(0.33 V)and an impressive mass activity of 2,750.42 mA·mg^−1 Pt under light illumination.It represents the highest MOR activity ever reported for photo-assisted electrocatalysts.Pt-MXene-TiO2 also shows excellent CO tolerance ability and stability,in which,after long-term(5,000 s)reaction,still keeps a high mass activity of 1,269.81 mA·mg−1Pt(62.66%of its initial activity).The photo-electro-catalytic system proposed in this work offers novel opportunities for exploiting photo-assisted enhancement of highly efficient and stable catalysts for MOR.

Carbon dots/Bi_(2)WO_(6) composite with compensatory photo-electronic effect for overall water photo-splitting at normal pressure

Overall water photo-splitting is a prospective ideal pathway to produce ultra-clean H_(2) energy by semiconductors.However,the band structure of many semiconductors cannot satisfy the requirement of H_(2) and O_(2) production at the same time.Herein,we illustrate that carbon dots(CDs)/Bi_(2)WO_(6) photocatalyst with compensatory photo-electronic effect has enhanced activity for overall water photo-splitting without any sacrificial agent.In this complex photocatalytic system,the photo-potential provided by CDs makes the CDs/Bi2WO6(C-BWO)composite could satisfy the band structure conditions for overall water photo-splitting.The C-BWO composite(3 wt%CDs content)exhibits optimized hydrogen evolution(oxygen evolution)of 0.28μmol/h(0.12μmol/h)with an approximate 2:1(H_(2):O_(2))stoichiometry at normal pressure.We further employed the in-situ transient photovoltage(TPV)technique to study the photoelectron extraction and the interface charge transfer kinetics of this composite catalyst.

Single-Metal-Atom Polymeric Unimolecular Micelles for Switchable Photocatalytic H_(2) Evolution

Developing“green”catalytic systems with desirable performance such as good water solubility,recyclability,and switchability is a great challenge.Here,to address this challenge,we extend the concept of polymeric unimolecular micelles(a typical selfassembled structure)to the construction of a stimuli-responsive and recoverable molecular catalyst with single-metal atoms that exhibits switchable photocatalytic activity for water splitting.