Ammonia Etching Research Articles

Adsorptive removal of ppb levels of boron trichloride using N-doped porous carbon materials

The removal of trace boron impurities (BCl3) in chlorosilane represents a significant challenge in polysilicon production. In this study, we employed the high-temperature ammonia etching method to fabricate nitrogen-doped porous carbon (NPC) adsorbents derived from lignite. The as-prepared NPCs were tested and evaluated as potential adsorbents for efficient removal of BCl3. Furthermore, a systematic investigation was conducted to assess the impact of contact time, initial concentration, adsorbent dose, and temperature. It was found that the adsorbent (NPC900) obtained at 900 °C exhibited an excellent efficacy in removing BCl3 (R% = 98.9 %), with a residual concentration of BCl3 in the solution was 1.65 ppb, which met the industrial requirements. This can be primarily attributed to its porous structure and high pyridinic-N content. Furthermore, the adsorption of BCl3 on NPC900 was better followed by Pseudo-second order kinetic model and the Langmuir isotherm model. Thermodynamic studies showed that the adsorption process was spontaneous and exothermic. The interactions between BCl3 and different nitrogen forms was analysis through the utilizing density functional theory (DFT) calculation. The findings indicate that pyridinic-N exhibits a stronger interaction with BCl3 (Eads = −102.35 kJ/mol), primarily due to the easier electron transfer from the nitrogen atom on pyridinic-N to BCl3.

Preparation of MoS2 nanosheets/nitrogen-doped carbon nanotubes/MoS2 nanoparticles and their electrochemical energy storage properties

Inferior electrical conductivity, huge volume swell, shuttle effect and slow redox reactions in Li-S batteries restrict their practical applications. In this study, molybdenum disulfide nanosheets anchored on nitrogen-doped carbon nanotubes encapsulating molybdenum disulfide nanoparticles (MoS2/NC/MoS2 NTs) were prepared by heat treatment, ammonia etching, high-temperature sulfurization, and solvent-thermal in-situ growth using polypyrrole-coated molybdenum trioxide nanorods (MoO3 NRs) as templates. The hollow structure of nitrogen-doped carbon nanotubes and the high specific surface area are conducive to increasing sulfur loading, increasing the contact area of electrolyte, accelerating the electron transport, and shortening the lithium ion transport route. The MoS2 nanosheets on the outer layer of the nitrogen-doped carbon tubes and the MoS2 particles wrapped inside can anchor polysulfides by chemisorption, slowing down the shuttle effect and enhancing the energy storage performance of lithium-sulfur batteries. The MoS2/NC/MoS2/S nanotubes (MoS2/NC/MoS2/S NTs) maintain a capacity of 498.9 mAh g−1 over 500 cycles at 1.0 A g−1, with an average single-cycle capacity decay rate of 0.061 %. The density functional theory calculations, the adsorption experiments, and the X-ray photoelectron spectroscopy results all confirm that the MoS2/NC/MoS2 NTs are able to anchor lithium polysulfides through strong adsorption, thus effectively mitigating the shuttle effect of polysulfides. The synthesis of MoS2/NC/MoS2/S NTs in this study is of important significance for the development of advanced lithium-sulfur batteries.

Structural energy storage composites based on etching engineering Fe-doped Co MOF electrode toward high energy density supercapacitors

Metal organic frameworks (MOFs) have been used widely as cathode materials for supercapacitors because of their adjustable chemical composition, variable topological structures, and relatively simple synthesis methods. However, most MOFs are insulated and their metal organic ligand coordination bonds are not stable enough in electrolytes, which greatly limits the application of MOFs in supercapacitors. The synergistic effect between transition metal doped and chemical etching is of great significance for the preparation of high-performance MOF electrodes. This study introduces Fe into Co MOF prepared by co precipitation to optimize the electronic structure of Co, and then constructed e-Fe-doped Co MOF hierarchical structure through ammonia etching. The Co MOF achieves rapid electron exchange at the electrode electrolyte interface through this synergistic effect, improving conductivity, and increasing specific surface area, exposing more active sites, effectively enhancing the electrochemical activity of the electrode. Therefore, the e-Fe-doped Co MOF-4 h has a high specific capacity of 700 C g−1 at 1 A g−1 with a 90.08 % high-rate performance. The assembled e-Fe-doped Co MOF-4 h//N-doped WC ASC provides the energy density of 80 Wh kg−1 at a power density of 800 W kg−1 with a ∼88 % capacitance retention after 10000 cycles. These results provide ideas for utilizing synergistic effects to prepare high-energy density supercapacitors using MOF materials.

Underwater Bubble Manipulation on Surfaces with Patterned Regions with Infused Lubricants.

The flexible manipulation of underwater gas bubbles on solid substrates has attracted considerable research interest from scientists in the fields of water electrolysis, bubble microreactions, drug delivery, and heat transfer. Inspired by the oxygen-binding mechanisms of aquatic organisms, scientists have designed a series of interfacial materials for use in collecting gases, detecting and grading bubbles, and conducting microbubble reactions. Aerophilic surfaces are commonly used in underwater bubble manipulation platforms due to their excellent gas-trapping properties. However, during bubble transport, some of the bubbles are retained in the rough structure of the aerophilic surface and cause gas loss, which in the long run reduces the gas transport function. In addition, the aerophilic surface is prone to failure in high-humidity and high-pressure underwater environments. The lubricant-infused surface features an oil layer that remains stable on a rough substrate and is immiscible with water. Additionally, the bubbles are transported over the oil layer without causing losses other than those dissolved in water. These attributes make it more favorable than the aerophilic surface. Inspired by the unique properties of Nepenthes and cactus spines, we developed a patterned slippery surface [patterned lubricant-infused surface (PLIS)] through laser etching and ammonia etching that facilitates the coexistence of superaerophobic and aerophilic surfaces. The PLIS executes bubble capture utilizing a difference in wettability measuring 78°, transports bubbles through Laplace force and buoyancy, and regulates bubble release by restricting the contact area on the PLIS. The PLIS can be prepared rapidly and affordably in just about an hour, and its potential for large-scale production is high. Following tests for shear, acid and alkali resistance, and corrosion resistance, the PLIS exhibited impressive weathering resistance and appears to have potential for application in some extreme environments.

Regulating valence states of CuFe-PBA for the simultaneous electrochemical detection of Cd2+, Pb2+ and Hg2+ in food application

Prussian blue analogues, as prospective electrode materials, play a crucial role in detecting heavy metal ions (HMIs), a process closely related to their electron transfer capacities and active surfaces. Here, etched copper-iron Prussian blue analogues (CuFe-PBA) are synthesized through a combination of flash nanoprecipitation (FNP) and an alkali etching process. Furthermore, this study investigates the impact of ammonia on the electronic structure of CuFe-PBA and its electrochemical detection capabilities for HMIs. The etched CuFe-PBA (e-CuFe-PBA) exhibits excellent detection performance for Cd2+, Pb2+ and Hg2+ with 17.6 μA μM−1, 24.2 μA μM−1 and 26.2 μA μM−1, respectively, due to the fact that the ammonia etching not only modulates the electronic properties of the surface of CuFe-PBA but also reduces the degree of agglomeration and enhances the accessible surface area. Additionally, it demonstrates excellent stability and resistance to interference, having been successfully applied to detect HMIs in food samples such as preserved eggs and apple juice. These results provide a new strategy for the use of Prussian blue analogues as electrochemical sensors for food safety applications.

Hollow prussian blue analog@defect-rich layered double hydroxide S-scheme heterojunctions toward optimized photothermal-photocatalytic performance

Effective photogenerated charge separation in the photocatalytic process is a crucial issue. Herein, hollow Prussian blue analog@defect-rich layered double hydroxide S-scheme heterojunctions are successfully obtained by two-sept etching strategies. Firstly, the hollow Prussian blue analog (H-PBA) is formed by ammonia etching. Subsequently, ZIF-67 is uniformly grown on the H-PBA surface and formed into defect-rich layered double hydroxide (D-LDH) nanocages by ion exchange. This hollow core–shell structure of H-PBA@D-LDH enables the photocatalyst to have more active sites. Meanwhile, in-situ XPS and the work function revealed the direction of electron transfer, providing evidence for the formation of S-scheme heterojunctions. In addition, transient photoluminescence and photoelectrochemical tests confirmed that the H-PBA@D-LDH S-scheme heterojunctions had longer charge lifetimes and enhanced photoelectrochemical properties. The presence of photothermal effect increases the temperature of the H-PBA@D-LDH composite system, which promotes the photocatalytic process. As a result, the H-PBA@D-LDH S-scheme heterojunction exhibited excellent photocatalytic degradation efficiency and hydrogen production rate (260.320 μmol h−1), which were several times higher than those of H-PBA and D-LDH. This work provides a new idea for the design of S-scheme photocatalysts.

Fabrication and Growth Mechanism of Nano-Octahedrons: A Study on Cu2O Core-Shell Structures for Oxygen Evolution Reaction

This paper explores the process and growth mechanism involved in fabricating nano-octahedrons. Using two key components, CTAB and hydrazine hydrate, leads to the formation of octahedral shapes. A Cu2O octahedral core–shell structure was successfully created by employing a coating technique, and its performance in the oxygen evolution reaction (OER) was thoroughly evaluated. Due to its high dispersibility in ammonia solution, Cu2O serves as an excellent representative for other components. Additionally, this chapter provides a detailed account of the production of octahedral nanocages through the ammonia etching method. Notably, the Cu2O nano octahedra demonstrate superior OER performance compared to commercial RuO2, exhibiting a significantly low overpotential of only 370 mV at 10 mA cm−2. These findings bear important implications for designing stable core/shell nanostructures and hollow structures by implementing appropriate chemicals while also deepening our understanding of the formation of octahedral shapes.

A process study of high-quality Zn(O,S) thin-film fabrication for thin-film solar cells

Abstract The Zn(O,S) thin film is considered a most promising candidate for a cadmium-free buffer layer of the Cu(In,Ga)Se2 (CIGS) thin-film solar cell due to its advantages of optical responses in the short-wavelength region and adjustable bandgap. In this paper, the thin-film growth mechanism and process optimization of Zn(O,S) films fabricated using the chemical bath deposition method are systematically investigated. The thickness and quality of Zn(O,S) films were found to be strongly affected by the concentration variation of the precursor chemicals. It was also revealed that different surface morphologies of Zn(O,S) films would appear if the reaction time were changed and, subsequently, the optimum reaction time was defined. The film-growth curve suggested that the growth rate varied linearly with the deposition temperature and some defects appeared when the temperature was too high. In addition, to further improve the film quality, an effective post-treatment approach was proposed and the experimental results showed that the microstructure of the Zn(O,S) thin film was improved by an ammonia etching process followed by an annealing process. For comparison purposes, both Zn(O,S)-based and CdS-based devices were fabricated and characterized. The device with a Zn(O,S)-CIGS solar cell after post-treatment showed near conversion efficiency comparable to that of the device with the CdS-CIGS cell.

Structural regulation of Fe–Co prussian blue analogues by incorporation of Pt for enhanced electrocatalytic overall water splitting

The specific properties of easy manufacturing, open frameworks, and high specific surface area endow prussian blue analogues (PBAs) as promising electrode materials for water splitting. Herein, we reported the successful application of interface engineering strategy to introduce low content of Pt species to boost the electrocatalytic activity of FeCo PBAs by ammonia etching and subsequent calcination. The resulting PtCo alloy modified FeCo PBAs (PtCo–FeCo PBAs) complex reveals modest electrocatalytic activity with low overpotentials (η) of 139 mV for hydrogen evolution reaction (HER) and 310 mV for oxygen evolution reaction (OER) at 10 mA cm−2 in alkaline electrolyte. Remarkably, the PtCo–FeCo PBAs only required small cell voltage of 1.68 V to drive 10 mA cm−2 for overall water splitting and the ideal electrocatalytic activity can be maintained for more than 50 h at a current density of 10 mA cm−2. The structural analysis unveils that the strong interaction between FeCo PBAs host and PtCo alloy resulting in charge redistribution and ultimately lead to high electrocatalytic activity and stability of PtCo–FeCo PBAs for both HER and OER.

Constructing porous carbon nitride nanosheets for efficient visible-light-responsive photocatalytic hydrogen evolution

The photocatalytic performance of polymeric carbon nitride (CN) is mainly restricted by the poor mass charge separation efficiency and poor light absorption due to its polymeric nature. The conventional strategies to address these problems involved constructing a nanosheets structure would result in a blue shifted light absorption and increased exciton binding energy. Here, with combination of ammonia etching and selectively hydrogen-bond breaking, holey carbon nitride nanosheets (hCNNS) were constructed, thus widening the light absorption range, and spontaneously shortening the migration distance of electrons and holes in the lateral and vertical directions, respectively. Further analysis also found out the reserved atomic structure order endowed hCNNS with the relatively high redox potential. When irradiated with visible light (λ > 420 nm) and loaded with 3 wt% Pt as the cocatalyst, the hydrogen evolution rate of hCNNS was about 40 times higher than the bulk CN, and the apparent quantum yield (AQY) of hCNNS is 1.47% at 435 ± 15 nm. We expect this research can provide a new sight for achieving highly efficient solar utilization of CN-based photocatalysts.

Constructing Oxygen Vacancies on Bi2MoO6 Nanosheets by Aqueous Ammonia Etching with Enhanced Photocatalytic NO Oxidation Performance

Constructing Oxygen Vacancies on Bi₂MoO₆ Nanosheets by Aqueous Ammonia Etching with Enhanced Photocatalytic NO Oxidation Performance

Scalable fabrication of NiCoMnO4 yolk-shell microspheres with gradient oxygen vacancies for high-performance aqueous zinc ion batteries

Defect regulation, which enables better charge transfer and capacity retention in manganese-based cathode materials, is the key to the development of rechargeable aqueous zinc-ion batteries. Herein, yolk-shell structured NiCoMnO4-VO with gradient oxygen vacancies are synthesized by spray pyrolysis and ammonia etching. The generation of the yolk-shell structures are regulated by the diffusion rate of ions in the atomized droplets during the nucleation process instead of adding template agent. In addition, the etching effect of ammonia gradually dissolves nickel oxide in the material from the surface to the interior, creating abounding gradient oxygen vacancies and thereby achieving more active sites for zinc storage and faster charge transfer. Therefore, the material exhibits superior electrochemical performances with initial discharge capacities of 277.9 mA h g−1 at 0.2 A g−1, and the long-term capacities retention rate is 89.3% after 2800 cycles at 5 A g−1. Ex-situ XRD demonstrates NiCoMnO4-VO belongs to the embedding-extraction mechanism of H+ and Zn2+. In-situ optical microscopy reveals that the formation of zinc dendrites is suppressed to some extent.

Numerical analysis of hole transport layer-free antimony selenide solar cells: Possible routes for efficiency promotion

Amongst the numerous absorbers confronted in thin-film solar cell technology, antimony selenide (Sb2Se3) is regarded as an extremely promising contender as it is a non-toxic and earth-abundant besides its high-level absorption coefficient. To boost the power conversion efficiency (PCE) of Sb2Se3 solar cells, we report some design recommendations by utilizing device simulation. The device model is firstly validated by calibration of an experimental cell having a configuration of FTO/CdS/Sb2Se3/Spiro-OMeTAD/Au. Then, the optimization of a hole transport layer (HTL) free structure is carried out by tuning the conduction band offset between the electron transport layer (ETL) and the Sb2Se3 absorber and by inspecting the key absorber parameters to get the maximum available power conversion efficiency. In this context, the ternary compound material ZnMgO is found to match the optimum band alignment. Moreover, the impact of ETL parameters, like thickness, doping, and surface treatment by ammonia etching, has been analyzed to understand its underlying physics and to provide possible ways for device efficiency promotion. All simulations, conducted in this paper, are accomplished by SCAPS device simulation software under standard one Sun (AM1.5G, 100 mW/cm2) illumination at 300 K.

Interface Etching Leads to the Inversion of the Conduction Band Offset between the CdS/Sb2Se3 Heterojunction and High-Efficient Sb2Se3 Solar Cells

Antimony selenide (Sb2Se3) has gained extensive attention owing to its excellent properties of stability and optoelectronic characteristics. However, the band-gap alignment of CdS/Sb2Se3 heterojunction is still a significant bottleneck in the improvement of the efficiency of Sb2Se3 thin-film solar cells. In this study, the quality of a vapor transport deposition (VTD)-processed Sb2Se3 thin film is improved by ammonia etching, wherein the surface potential of the CdS buffer layer is modified and the band-gap alignment of CdS/Sb2Se3 is changed from a “clifflike” to a “spikelike” structure. Moreover, the growth orientation of the Sb2Se3 absorber is tailored. Finally, the reduced carrier recombination, improved band-gap structure, and enhanced crystal orientation lead to the fabrication of a Sb2Se3 solar cell with the best efficiency of 7.48% in this work, which is comparable with the highest efficiency of VTD-processed Sb2Se3 thin-film solar cells. This is expected to provide a valuable reference for the future development of Sb2Se3 thin-film solar cells and other photoelectronic devices.

Enhanced electrocatalytic performance of N-doped carbon xerogels obtained through dual nitrogen doping for the oxygen reduction reaction.

The development of high efficiency and low-cost electrocatalysts for the oxygen reduction reaction (ORR) is urgently desired for many energy storage and conversion systems. Nitrogen-doped carbon xerogels (NCXs) which have been successfully applied as effective electrocatalysts for the ORR have continued to attract attention due to their competitive price and tunable surface chemistry. A new dual N-doped NCX (NCoNC) electrocatalyst is fabricated as a carbon based catalyst though a facile impregnation of peptone in a precursor and ammonia etching pyrolysis method. XPS analysis demonstrates that the NCoNC electrocatalyst not only has a high N doping amount, but also has an optimized chemical state composition of N doping, which play an important role in improving the microstructure and catalytic performance of the catalysts. XRD and HRTEM results show that the doped metal nano-particles are coated with a double carbon layer of graphene carbon (inner layer) and amorphous carbon (outer layer) forming serrated edges that facilitate the ORR process. The as-obtained NCoNC catalyst exhibits good electrocatalytic performance and excellent stability for the ORR in both acidic and alkaline environments. In particular, in alkaline electrolyte, the decrements of both the limiting current density and the half-wave potential of the NCoNC catalyst were significantly lower than those of a commercial Pt/C catalyst during accelerated aging tests. When serving as an air electrode in Zn–air batteries, the catalyst also exhibits superior catalytic performance with a peak power density of 78.2 mW cm−2 and a stable open-circuit voltage of 1.37–1.43 V. This work presents a novel tactic to regulate the microstructure and composition of carbon-based electrocatalysts by the facile and scalable dual-effect nitrogen doping method which may be conducive to promoting and developing highly efficient and promising electrocatalysts for the ORR.

Microwave-assisted synthesis of bio-based Ni@NSiC nanocomposites for high efficient electrocatalysis of glucose

In the present study, the magnolia leaf was used as the carbon source to synthesize a sustainable high-efficiency electro-catalytic material via a microwave-assisted synthesis approach. The carbon shell-wrapped nickel nanoparticles were grown in situ on 3D silica carbon-based nanoclusters to prepare NiSiO3/CNX biomass nanocomposites. Ni@NSiC-900 nitrogen-doped nanocomposite was obtained under ammonia etching at 900 °C. The prepared Ni@NSiC nanocomposite was characterized by SEM, XPS, XRD and TEM technologies. Results showed that the prepared material had moderate lattice defects and excellent electrocatalytic performance for glucose detection. The distinctive electrochemical performance might be illustrated by the ultra-thin carbon shell, high conductivity of highly uniformly dispersed nickel nanoparticles and SiO2/CNX substrate. In order to further investigate its electrochemical application, Ni@NSiC-900 was applied to construct a sensing platform for glucose detection, the obtained sensitivity, response time, detection limit and linear range was 282.38 µAcm−2 mM−1, 1.2 s, 1.23 µM and up to 8145.75 µM, respectively. Studies with ascorbic, uric acid, dopamine, lactose, fructose and maltose showed that their interference with glucose measurement was negligible or overcame, and an excellent analytical performance was obtained in the actual sample analysis. The obtained results in this study implicated that the nanocomposite was a potential practical candidate for biosensors materials.

Ammonia Etching to Generate Oxygen Vacancies on CuMn2O4 for Highly Efficient Electrocatalytic Oxidation of 5-Hydroxymethylfurfural

Ammonia Etching to Generate Oxygen Vacancies on CuMn₂O₄ for Highly Efficient Electrocatalytic Oxidation of 5-Hydroxymethylfurfural

Hydrothermally structured superhydrophobic surface with superior anti-corrosion, anti-bacterial and anti-icing behaviors

Corrosion and biofoulings are ubiquitous problems with detrimental impact for a variety of industries. Transforming intrinsically hydrophilicity of metallic surface to be non-wetting superhydrophobicity is highly desired for acquiring protective surfaces. In this paper, hydrothermal structured superhydrophobic surfaces were fabricated on aluminum alloy substrates through ammonia etching followed with 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTES) modification. The surface morphologies, roughness, chemical compositions and the relationship between hydrothermal parameters and wettability transition were systematically investigated. Besides, the self-cleaning ability, corrosion resistance, NaCl deliquescence behavior, anti-bacterial and anti-icing properties were evaluated. The results demonstrated a remarkably improved charge transfer resistance ( R ct ), high anti-bacterial efficiency towards E. coli and S. aureus bacteria and significantly enhanced anti-icing performance. We believe the superior corrosion resisting, bacterial suppression and ice over delay performance of superhydrophobic metallic materials will exhibit promising applications in various industrial fields. • Superhydrophobic surface was achieved by hydrothermal etching and molecule grafting. • The wettability plays a key role in determining the properties of the surface. • The charge transfer resistance of superhydrophobic surface was greatly enhanced. • NaCl deliquescence behavior suggests potential atmospheric corrosion inhibition. • The superhydrophobic surface exhibit improved anti-bacterial and anti-icing properties.

N-doped carbon-coated Fe3N composite as heterogeneous electro-Fenton catalyst for efficient degradation of organics

Herein, the application of a N-doped graphitic-carbon-coated iron nitride composite dispersed in a N-doped carbon framework (Fe3N@NG/NC) is investigated as a heterogeneous electro-Fenton (HE-EF) catalyst for the efficient removal of organics. The simultaneous carbonization and ammonia etching of iron-based metal organic framework (Fe-MOF) materials yielded well-dispersed N-doped carbon-coated Fe3N nanoparticles with a diameter of ~70 nm. The Fe3N and pyridinic N endowed the composite with high HE-EF activity for decomposing the electrogenerated H2O2 to •OH. The Fe3N@NG/NC exhibited outstanding HE-EF performance in removing various organic pollutants with low iron leaching. A removal rate of 97–100% could be obtained for rhodamine B (RhB), dimethyl phthalate, methylene blue, and orange II in 120 min at a pH of 5.0. When the solution pH was set to 3.0, 5.0, 7.0, and 9.0, the removal rate of RhB reached 100%, 96%, 92%, and 81%, respectively, in 60 min at an optimum voltage of 0.0 V (vs. reversible hydrogen electrode (RHE)). Moreover, the concentration of leached iron was expected to be below 0.03 mg/L in a wide pH range of 3.0–9.0. In addition, the RhB removal efficiency remained as high as 90% after six cycles in the reusability experiments. This work highlights the MOF-derived Fe3N composite as an efficient HE-EF catalyst and the corresponding catalytic mechanism, which facilitates its application in wastewater treatment.

Pd Ion‐Exchange and Ammonia Etching of a Prussian Blue Analogue to Produce a High‐Performance Water‐Splitting Catalyst

AbstractThe authors report an ammonia‐assisted in situ cation‐exchange method for the synthesis of dodecagon N‐doped PdCoNi carbon‐based nanosheets (Pd‐e‐NiCo‐PBA‐C) and explore the catalytic performance. Pd‐e‐NiCo‐PBA‐C exerts extremely low overpotential and Tafel slope for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) both in acidic and alkaline media, only 47 mV, 55 mV dec−1 (pH = 0, HER) and 147 mV, 67 mV dec−1 (pH = 14, HER), and 309 mV, 67 mV dec−1 (pH = 14, OER), outperforming commercial IrO2‐based and Pt‐based catalysts. In addition, after 5000 cycles, the linear sweep voltammetry curve shows a negligible shift, indicating excellent stability performance. To test its overall water‐splitting performance, Pd‐e‐NiCo‐PBA‐C is applied as both cathode and anode materials. A high current density of 33 mA cm−2 at a battery voltage of 1.6 V is obtained, with the catalytic activity maintained at 97.3% after over 50 h. To get a further insight into the superior OER and HER performance, theoretical calculations are carried out, the better performance originates from the affinity difference of Pd and Ni atoms for gas atoms, and the replacement of inert atoms can decrease the binding energy and enhance the electrocatalytic activity.