Simulation of fixed-bed adsorption process considering particle size distribution

The distribution of adsorbent particle sizes typically has a significant impact on adsorption performance.Most fixed-bed adsorption studies adopt the assumption of average particle size to simplify the adsorption model,but this does not eliminate the deviation between experiments and simulations caused by particle size distribution in practice.In this study,the population balance equation(PBE)and fixed-bed adsorption kinetics model were combined to simulate the adsorption process in a fixed-bed reactor,modeling the distribution of adsorbate uptake over time on adsorbent particles of different sizes.We integrated and optimized the PBE and fixed-bed mass transfer model in the algorithm,and the resulting combined model adopts a variable time step size,which can achieve a balance between computational efficiency and error while ensuring computational convergence.By slicing the model in the spatial dimension,multiple sets of PBE can be calculated in parallel,improving computational efficiency.The adsorption process of single-component and multi-component CO_(2)/CH_(4)/N_(2)on 4A zeolite without binder was simulated,and the influence of adsorbent particle size distribution was analyzed.Simulation results show that the assumption of average adsorbent particle size,which was commonly made in published work,will underestimate the time required for adsorbates to break through the fixed bed compared with the assumption of uniform adsorbent particle size.This model helps to consider the impact of adsorbent particle size distribution on the adsorption process,thereby improving the prediction accuracy of adsorbent performance.

Aspen Adsorption在气体吸附过程模拟方面的应用

Aspen Adsorption是一款吸附模拟软件,常用于气体吸附分离过程的模拟计算,对操作条件优化、设计优化、吸附材料性能评价等方面具有一定的指导作用。简要介绍了Aspen Adsorption软件的应用、模型参数和各种衡算方程,总结了其在穿透曲线计算方面的模拟计算和应用,归纳了利用循环控制器Cycle Organizer针对各种类型的变压吸附PSA(Pressure Swing Adsorption)和变温吸附TSA(Temperature Swing Adsorption)过程进行模拟的情况。此外,针对Aspen Adsorption与其他软件结合使用的案例也进行了简要介绍。最后对Aspen Adsorption的未来发展进行了展望。

Fixed-Bed Column Adsorption Modeling of MnO4- Ions from Acidic Aqueous Solutions on Activated Carbons Prepared with the Biomass

Activated carbons calcined at 400˚C and 600˚C (AC-400 and AC-600), prepared using palm nuts, collected in the town of Franceville in Gabon, were used to study the dynamic adsorption of MnO4- ions in acidic media on fixed bed column and on the kinetic modeling of experimental data of breakthrough curves of MnO4- ions obtained. Results on the adsorption of MnO4- ions in fixed-bed dynamics obtained on AC-400 and AC-600 adsorbents beds indicated that the AC-400 bed appears to be the most efficient in removing MnO4- ions in acidic media. Indeed, the adsorbed amounts, the adsorbed capacities at saturation and the elimination percentage of MnO4- ions obtained with AC-400 (31.24 mg;52.06 mg·g-1 and 41.65% respectively) were higher compared to those obtained with AC-600 (9.87 mg;16.45 mg·g-1 and 17.79% respectively). The breakthrough curves kinetic modeling revealed that the Thomas model and the pseudo-first-order kinetic model were the most suitable models to describe the adsorption of MnO4- ions on adsorbents studied in our experimental conditions. The results of the intraparticle diffusion model showed that intraparticle diffusion was involved in the adsorption mechanism of MnO4- ions on investigated adsorbents and was not the limiting step and the only process controlling MnO4- ions adsorption. In contrast to AC-400, the intraparticle diffusion on AC-600 bed plays an important role in the adsorption mechanism of MnO4- ions.

Review:Mathematically modeling fixed-bed adsorption in aqueous systems

Adsorption is one of the widely used processes in the chemical industry environmental application.As compared to mathematical models proposed to describe batch adsorption in terms of isotherm and kinetic behavior,insufficient models are available to describe and predict fixed-bed or column adsorption,though the latter one is the main option in practical application.The present review first provides a brief summary on basic concepts and mathematic models to describe the mass transfer and isotherm behavior of batch adsorption,which dominate the column adsorption behavior in nature.Afterwards,the widely used models developed to predict the breakthrough curve,i.e.,the general rate models,linear driving force(LDF) model,wave propagation theory model,constant pattern model,Clark model,Thomas model,Bohart-Adams model,Yoon-Nelson model,Wang model,Wolborska model,and modified dose-response model,are briefly introduced from the mechanism and mathematical viewpoint.Their basic characteristics,including the advantages and inherit shortcomings,are also discussed.This review could help those interested in column adsorption to reasonably choose or develop an accurate and convenient model for their study and practical application.

Mass transfer mechanisms in fixed-bed adsorption of erythromycin

The equilibrium and kinetic characteristics of the adsorption of erythromycin to Sepabeads SP825 were determined.The equilibrium data in a batch system was well described by a Langmuir isotherm.The separation performance was investigated in a fixed-bed system with respect to the adsorption superficial velocity,ionic strength and pH.A mathematical model was used to simulate the mass transfer mechanism,taking film mass transfer,pore diffusion and axial dispersion into account.The model predictions were consistent with the experi-mental data and were consequently used to determine the mass transfer coefficients.

Analysis of CH_(4) and H_(2) Adsorption on Heterogeneous Shale Surfaces Using aMolecular Dynamics Approach

Determining the adsorption of shale gas on complex surfaces remains a challenge in molecular simulation studies.Difficulties essentially stem from the need to create a realistic shale structure model in terms of mineral heterogeneityand multiplicity.Moreover,precise characterization of the competitive adsorption of hydrogen andmethane in shale generally requires the experimental determination of the related adsorptive capacity.In thisstudy,the adsorption of adsorbates,methane(CH_(4)),and hydrogen(H_(2))on heterogeneous shale surface modelsof Kaolinite,Orthoclase,Muscovite,Mica,C_(60),and Butane has been simulated in the frame of a moleculardynamic’s numerical technique.The results show that these behaviors are influenced by pressure and potentialenergy.On increasing the pressure from 500 to 2000 psi,the sorption effect for CH_(4)significantly increasesbut shows a decline at a certain stage(if compared to H_(2)).The research findings also indicate that raw shalehas a higher capacity to adsorb CH_(4)compared to hydrogen.However,in shale,this difference is negligible.

Adsorption,in vitro digestion and human gut microbiota regulation characteristics of three Poria cocos polysaccharides

Poria cocos(PC)is a famous traditional Chinese medicine(TCM)and a widely used healthcare ingredient,which has antiobesity,enhancing immunity and improving sleep effects.Traditionally,only water-soluble poria polysaccharide(WSP)is extracted and applied for clinical application,while insoluble polysaccharide(alkali-soluble poria polysaccharide,ASP)is discarded as herb residue.However,the whole PC has also been historically utilized as functional herbal food.Considering the beneficial role of dietary fiber and the traditional use of PC,ASP may also contribute substantially to the therapy function of PC.Compared to WSP,little attention has been paid to ASP and ASP modified product carboxymethyl poria polysaccharide(CMP)which has been used as an antitumor adjuvant drug.In this study,the oil,cholesterol,metal ions and polyphenols adsorption ability,in vitro simulated digestive and the gut microbiota fermentation characteristics of WSP,ASP and CMP were studied to evaluate the functional values of three P.cocos polysaccharides(PCPs).The results showed that all three PCPs had good adsorption capacity on cholesterol,polyphenols and metal ions(Cd^(2+)/Zn^(2+)/Mg^(2+)),among which ASP showed the highest capacity than WSP and CMP.The adsorption capacity of all three PCPs on heavy metal ions(Cd^(2+)/Zn^(2+))was stronger than that of non-heavy metal ions(Mg^(2+));The in vitro digestibility of all three PCPs was very low,but WSP was slightly higher than ASP and CMP;Moreover,the indigestible residue of all three PCPs could improve the richness and diversity of gut microbiota,among which ASP had the greatest influence.In general,ASP and CMP could significantly promote the proliferation of some probiotics and inhibit the growth of some harmful bacteria.The gut microbiota diversity of CMP was reduced,but the richness of probiotics,especially Parabacteroides distasonis was significantly enhanced compared with the ASP group,and the growth of harmful bacteria Klebsiella pneumoniae was inhibited after CMP treatment.The short-chain fatty acids(SCFAs)analysis results showed that all three PCPs could significantly promote the production of acetic acid,propionic acid and the total acid content compared with blank control group,and SCFAs producing activity was positively correlated with the proliferative capacity of probiotics.Taken together,the good adsorption characteristics and gut microbiota regulatory activity of ASP may lay foundation for its lipid-lowering and immune-improving function.Additionally,the probiotic effect of CMP and ASP indicated that except for only use the water extract of PC in clinic,CMP and ASP also can be used in healthcare to take full advantage of this valuable medicine.

High adsorption selectivity of activated carbon and carbon molecular sieve boosting CO_(2)/N_(2) and CH_(4)/N_(2) separation

Flue gas and coal bed methane are two important sources of greenhouse gases.Pressure swing adsorption process has a wide range of application in the field of gas separation,and the selection of adsorbent is crucial.In this regard,in order to assess the better adsorbent for separating CO_(2) from flue gas and CH_(4) from coal bed methane,adsorption isotherms of CO_(2),CH_(4) and N_(2) on activated carbon and carbon molecular sieve are measured at 303.15,318.15 and 333.15 K,and up to 250 kPa.The experimental data fit better with Langmuir 2 compared to Langmuir 3 and Langmuir-Freundlich models,and Clausius-Clapeyron equation was used to calculate the isosteric heat.Both the order of the adsorbed amount and the adsorption heat on the two adsorbents are CO_(2)>CH_(4)>N_(2).The adsorption kinetics are calculated by the pseudo-first kinetic model,and the order of adsorption rates on activated carbon is N_(2)-CH_(4)>CO_(2),while on carbon molecular sieve,it is CO_(2)-N_(2)>CH_(4).It is shown that relative molecular mass and adsorption heat are the primary effect on kinetics for activated carbon,while kinetic diameter is the main resistance factor for carbon molecular sieve.Moreover,the adsorption selectivity of CH_(4)/N_(2) and CO_(2)/N_(2) were estimated with the ideal adsorption solution theory,and carbon molecular sieve performed best at 318.15 K for both CO_(2) and CH_(4) separation.The study suggested that activated carbon is a better choice for separating flue gas and carbon molecular sieve can be a strong candidate for separating coal bed methane.

Fate and Behavior of Tetracycline Resistance Genes in Activated Carbon Adsorption

The accessibility of tetracycline resistance gene (tetG) into the pores of activated carbon (AC), as well as the impact of the pore size distribution (PSD) of AC on the uptake capacity of tetG, were investigated using eight types of AC (four coal-based and four wood-based). AC showed the capability to admit tetG and the average reduction of tetG for coal-based and wood-based ACs at the AC dose of 1 g·L-1 was 3.12 log and 3.65 log, respectively. The uptake kinetic analysis showed that the uptake of the gene followed the pseudo-second-order kinetics reaction, and the uptake rate constant for the coal-based and wood-based ACs was in the range of 5.97 × 10-12 - 4.64 × 10-9 and 7.02 × 10-11 - 1.59 × 10-8 copies·mg-1·min-1, respectively. The uptake capacity analysis by fitting the obtained experiment data with the Freundlich isotherm model indicated that the uptake constant (KF) values were 1.71 × 103 - 8.00 × 109 (copies·g-1)1-1/n for coal-based ACs and 7.00 × 108 - 3.00 × 1010 (copies·g-1)1-1/n for wood-based ones. In addition, the correlation analysis between KF values and pore volume as well as pore surface at different pore size regions of ACs showed that relatively higher positive correlation was found for pores of 50 - 100 Å, suggesting ACs with more pores in this size region can uptake more tetG. The findings of this study are valuable as reference for optimizing the adsorption process regarding antibiotic resistance-related concerns in drinking water treatment.

Investigations of methane adsorption characteristics on marine-continental transitional shales and gas storage capacity models considering pore evolution

Methane adsorption is a critical assessment of the gas storage capacity(GSC)of shales with geological conditions.Although the related research of marine shales has been well-illustrated,the methane adsorption of marine-continental transitional(MCT)shales is still ambiguous.In this study,a method of combining experimental data with analytical models was used to investigate the methane adsorption characteristics and GSC of MCT shales collected from the Qinshui Basin,China.The Ono-Kondo model was used to fit the adsorption data to obtain the adsorption parameters.Subsequently,the geological model of GSC based on pore evolution was constructed using a representative shale sample with a total organic carbon(TOC)content of 1.71%,and the effects of reservoir pressure coefficient and water saturation on GSC were explored.In experimental results,compared to the composition of the MCT shale,the pore structure dominates the methane adsorption,and meanwhile,the maturity mainly governs the pore structure.Besides,maturity in the middle-eastern region of the Qinshui Basin shows a strong positive correlation with burial depth.The two parameters,micropore pore volume and non-micropore surface area,induce a good fit for the adsorption capacity data of the shale.In simulation results,the depth,pressure coefficient,and water saturation of the shale all affect the GSC.It demonstrates a promising shale gas potential of the MCT shale in a deeper block,especially with low water saturation.Specifically,the economic feasibility of shale gas could be a major consideration for the shale with a depth of<800 m and/or water saturation>60%in the Yushe-Wuxiang area.This study provides a valuable reference for the reservoir evaluation and favorable block search of MCT shale gas.

The flow behavior of droplet adsorption on a liquid-liquid interface accompanied by cross-linking reaction and phase separation in a microchannel

The adsorption process of droplets on the liquid-liquid interface and phase separation process can regulate the spatial distribution of the fluid system,which are crucial for chemical engineering.However,the cross-linking reaction,which is widely used in the field of polymers,can change the physical properties of the fluids and affect the flow behavior accordingly.A configuration of microchannels is designed to conveniently generate uniform droplets in one phase of the parallel flow.The flow behavior of the adsorption process of sodium alginate droplets on the liquid-liquid interface is investigated,and the subsequent process of phase separation is studied.In the process of droplet adsorption,the crosslinking reaction occurs synchronously,which makes the droplet viscosity and the elasticity modules of the droplet surface increase,thus affecting the dynamics of the adsorption process and the equilibrium shape of the droplet.The variation of the adsorption length with time is divided into three stages,which all conform to power law relationship.The exponents of the second and third stages deviate from the results of the Tanner's law.The flow pattern maps of droplet adsorption and phase separation are drawn,and the operating ranges of complete adsorption and complete separation are provided.This study provides a theoretical basis for further studying the flow behavior of droplets with cross-linking reaction in a microchannel.

Green Synthesis of Iron(Ⅱ,Ⅲ)-polyphenol Nanoparticles and Their Adsorption of Malachite Green

Three kinds of iron nanoparticles(FeNPs)were prepared via green route based on pomegranate(PG),green tea(GT),and mulberry(ML)extracts under ambient conditions.The obtained materials were characterized by scanning electron microscopy(SEM),transmission electronic microscopy(TEM),X-ray energy-dispersive spectrometer(EDS),X-ray diffraction(XRD),fourier transform infrared spectroscopy(FTIR),and X-ray photoelectron spectroscopy(XPS)techniques.The experimental results show that FeNPs were in the form of amorphous iron(Ⅱ,Ⅲ)-polyphenol complex with different dispersity and morphologies.GT-Fe has the smallest size range of 25-35 nm,PG-Fe has a moderate size-distribution of 30-40 nm,while ML-Fe formed a tuberous net-type with a sheeting structure.PG-Fe displays the highest removal efficiency of 90.2%in 20 min towards cationic dye of malachite green(16.6%by ML-Fe and 69.3%by GT-Fe),which is attributed to its highest polyphenol content,lowest zeta potential,as well as the most Fe^(2+)on the surface of FeNPs.The removal mechanism was mainly induced by electrostatic adsorption based on pH and zeta potential tests.

Enhanced nitrite electroreduction to ammonia via interfacial dual-site adsorption

The nitrite(NO_(2)^(−))to ammonia(NH3)electroreduction reaction(NO_(2)^(−)RR)would be impeded by sluggish proton-coupled electron transfer kinetics and competitive hydrogen evolution reaction(HER).A key to improving the NH_(3) selectivity is to facilitate adsorption and activation of NO_(2)^(−),which is generally undesirable in unitary species.In this work,an efficient NO_(2)^(−)RR catalyst is constructed by cooperating Pd with In2O3,in which NO_(2)^(−)could adsorb on interfacial dual-site through“Pd–N–O–In”linkage,leading to strengthened NO_(2)^(−)adsorption and easier N=O bond cleavage than that on unitary Pd or In2O3.Moreover,the Pd/In_(2)O_(3)composite exhibits moderate H^(*)adsorption,which may facilitate protonation kinetics while inhibiting competitive HER.As a result,it exhibits a fairly high NH_(3)yield rate of 622.76 mmol h^(−1)g^(−1)cat with a Faradaic efficiency(FE)of 95.72%,good selectivity of 91.96%,and cycling stability towards the NO_(2)^(−)RR,surpassing unitary In_(2)O_(3)and Pd/C electrocatalysts.Besides,computed results indicate that NH_(3)production on Pd/In_(2)O_(3)follows the deoxidation to hydrogenation pathway.This work highlights the significance of H^(*)and NO_(2)^(−)adsorption modulation and N=O activation in NO_(2)^(−)RR electrochemistry by creating synergy between a mediocre catalyst with an appropriate cooperator.

Ultra-high specific surface area activated carbon from Taihu cyanobacteria via KOH activation for enhanced methylene blue adsorption

Cyanobacteria-based activated carbon(CBAC)was successfully prepared by pyrolysis-activation of Taihu cyanobacteria.When the impregnation ratio and activated temperature were 2 and 800-C,respectively,the optimal CBACs possessed an ultra-high specific surface(2178.90 m^(2)·g^(-1))and plenty of micro-and meso-pores,as well as a high pore volume(1.01 cm^(3)·g^(-1)).Ascribed to ultra-high surface area,π-π interaction,electrostatic interaction,as well as hydrogen-bonding interactions,the CBACs displayed huge superiority in efficient dye removal.The saturated methylene blue adsorption capacity by CBACs could be as high as 1143.4 mg·g^(-1),superior to that of other reported biomass-activated carbons.The adsorption was endothermic and modeled well by the pseudo-second-order kinetic,intra-particle diffusion,and Langmuir models.This work presented the effectiveness of Taihu cyanobacteria adsorbent ascribed to its super large specific surface area and high adsorption ability.

Corrosion-Resistant Polymer-Derived SiOC Membrane for Effective Organic Removal via Synergistic Adsorption and Peroxymonosulfate Activation

A major challenge is to construct ceramic membranes with tunable structures and functions for water treatment.Herein,a novel corrosion-resistant polymer-derived silicon oxycarbide(SiOC)ceramic membrane with designed architectures was fabricated by a phase separation method and was applied in organic removal via adsorption and oxidation for the first time.The pore structure of the as-prepared SiOC ceramic membranes was well controlled by changing the sintering temperature and polydimethylsiloxane content,leading to a pore size of 0.84–1.62μm and porosity of 25.0–43.8%.Corrosion resistance test results showed that the SiOC membranes sustained minimal damage during 24 h exposure to high-intensity acid–base conditions,which could be attributed to the chemical inertness of SiOC.With rhodamine 6G(R6G)as the model pollutant,the SiOC membrane demonstrated an initial eff ective removal rate of 99%via adsorption;however,the removal rate decreased as the system approached adsorption saturation.When peroxymonosulfate was added into the system,efficient and continuous degradation of R6G was observed throughout the entire period,indicating the potential of the as-prepared SiOC membrane in oxidation-related processes.Thus,this work provides new insights into the construction of novel polymer-derived ceramic membranes with well-defined structures and functions.

A green cross-linking method for the preparation of renewable threedimensional graphene sponges for efficient adsorption of Congo red dye

Graphene-based materials possess significant potential for the treatment of dye wastewater due to their exceptional adsorption properties toward stubborn pollutants.However,their utilization is hindered by high preparation costs,low yields,environmental pollution during synthesis,and challenges in regenerating the adsorbent.This study proposes a novel approach to address these limitations by developing nitrogen-doped three-dimensional(3D)polyvinyl alcohol(PVA)crosslinked graphene sponges(N-PGA)using a cross-linking method with ammonium carbonate.This method offers a relatively mild,environmentally friendly approach.Ammonium carbonate serves as both a reducing and modifying agent,facilitating the formation of the intrinsic structure of N-PGA and acting as a nitrogen source.Meanwhile,PVA is utilized as the cross-linking agent.The results demonstrate that N-PGA exhibits a favorable internal 3D hierarchical porous structure and possesses robust mechanical properties.The measured specific surface area(BET)of N-PGA was as high as406.538 m^(2)·g^(-1),which was favorable for its efficient adsorption of Congo red(CR)dye molecules.At an initial concentration of 50 mg·L^(-1),N-PGA achieved an impressive removal rate of 89.6%and an adsorption capacity of 112 mg·g^(-1)for CR dye.Furthermore,it retained 79%of its initial adsorption capacity after 10 cycles,demonstrating excellent regeneration performance.In summary,the synthesized N-PGA displays remarkable efficacy in the adsorption of CR dye in wastewater,opening up new possibilities for utilizing 3D porous graphene nanomaterials as efficient adsorbents in wastewater treatment.

High-performance ZIF-8 membranes:preparation and their uranium adsorption performance

In this study,the ZIF-8 membrane(ZIF-8/PP-g-MAH)is prepared by in situ synthesis of ZIF-8 on irradiation-pretreated polymer substrates to improve the uranium adsorption performance and address the recycling problems of ZIF-8 powder.The effects of pH,contact time,and uranium concentration on the adsorption of ZIF-8/PP-g-MAH were investigated.Adsorption isotherm and kinetics analysis show that ZIF-8/PP-g-MAH has a high adsorption capacity of 478.5 mg/g,which is 1.26 times higher than that of ZIF-8,and a rapid adsorption equilibrium of 120 min,which is shortened to one-third of that required for ZIF-8(360 min).The adsorption process of ZIF-8/PP-g-MAH is consistent with that of the Langmuir isotherm and pseudo-second-order dynamic model.ZIF-8/PP-g-MAH also exhibits good selectivity for uranium in simulated seawater.The high adsorption performance of ZIF-8/PP-g-MAH is attributed to its membrane structure,which improves the utilization of coordination sites,including Zn-OH,C-N,and C=N.This study provides an efficient adsorption material for rapid uranium extraction,thus promoting the development of uranium extraction technologies.

Density functional theory study of B- and Si-doped carbons and their adsorption interactions with sulfur compounds

Understanding the adsorption interactions between carbon materials and sulfur compounds has far-reaching impacts,in addition to their well-known important role in energy storage and conversion,such as lithium-ion batteries.In this paper,properties of intrinsic B or Si single-atom doped,and B-Si codoped graphene(GR)and graphdiyne(GDY)were investigated by using density functional theory-based calculations,in which the optimal doping configurations were explored for potential applications in adsorbing sulfur compounds.Results showed that both B or Si single-atom doping and B-Si codoping could substantially enhance the electron transport properties of GR and GDY,improving their surface activity.Notably,B and Si atoms displayed synergistic effects for the codoped configurations,where B-Si codoped GR/GDY exhibited much better performance in the adsorption of sulfurcontaining chemicals than single-atom doped systems.In addition,results demonstrated that,after B-Si codoping,the adsorption energy and charge transfer amounts of GDY with sulfur compounds were much larger than those of GR,indicating that B-Si codoped GDY might be a favorable material for more effectively interacting with sulfur reagents.

Mechanism study of Cu(Ⅱ) adsorption from acidic wastewater by ultrasonic-modified municipal solid waste incineration fly ash

High concentrations of copper ions(Cu(Ⅱ)) in water will pose health risks to humans and the ecological environment. Therefore, this study aims to utilize ultrasonic-cured modified municipal solid waste incineration(MSWI) fly ash for Cu(Ⅱ) adsorption to achieve the purpose of “treating waste by waste.” The effects of p H, adsorption time, initial concentration, and temperature on the modified MSWI fly ash’s adsorption efficiency were systematically studied in this article. The adsorption performance of the modified MSWI fly ash can be enhanced by the ultrasonic modification. At pH = 2, 3 and 4, the adsorption capacity of the modified MSWI fly ash for Cu(Ⅱ) increased by 2.7, 1.9 and 1.2 times, respectively. Furthermore, it was suggested that the adsorption process of the modified MSWI fly ash can be better simulated by the pseudo-second-order kinetic model, with a maximum adsorption capacity calculated by the Langmuir model of 24.196 mg.g-1. Additionally, the adsorption process is spontaneous,endothermic, and chemisorption-dominated from the thermodynamic studies(ΔH and ΔS > 0, ΔG < 0).Finally, the enhanced adsorption performance of the modified MSWI fly ash for Cu(Ⅱ) may be attributed to electrostatic interaction and chelation effects.

Balancing electron transfer and intermediate adsorption ability of metallic Ni-Fe-RE-P bifunctional catalysts via 4f-2p-3d electron interaction for enhanced water splitting

Balancing electron transfer and intermediate adsorption ability of bifunctional catalysts via tailoring electronic structures is crucial for green hydrogen production,while it still remains challenging due to lacking efficient strategies.Herein,one efficient and universal strategy is developed to greatly regulate electronic structures of the metallic Ni-Fe-P catalysts via in-situ introducing the rare earth(RE)atoms(Ni-Fe-RE-P,RE=La,Ce,Pr,and Nd).Accordingly,the as-prepared optimal Ni-Fe-Ce-P/CC self-supported bifunctional electrodes exhibited superior electrocatalytic activity and excellent stability with the low overpotentials of 247 and 331 mV at 100 mA cm^(-2) for HER and OER,respectively.In the assembled electrolyzer,the Ni-Fe-Ce-P/CC as bifunctional electrodes displayed low operation potential of 1.49 V to achieve a current density of 10 mA cm^(-2),and the catalytic performance can be maintained for 100 h.Experimental results combined with density functional theory(DFT)calculation reveal that Ce doping leads to electron decentralization and crystal structure distortion,which can tailor the band structures and d-band center of Ni-Fe-P,further increasing conductivity and optimizing intermediate adsorption energy.Our work not only proposes a valuable strategy to regulate the electron transfer and intermediate adsorption of electrocatalysts via RE atoms doping,but also provides a deep under-standing of regulation mechanism of metallic electrocatalysts for enhanced water splitting.