Excessive Doping Research Articles

Study of the photovoltaic properties of Cs and Cl co-doped FAPbI3 based on first principles

Formamidine lead iodide perovskite (FAPbI3) is often used as a light-absorbing layer in solar cells to alleviate the energy crisis because of its good photovoltaic properties. However, its lack of stability is also an obstacle to the current development. It has been found that doping with different kinds of elements at different sites can enhance its stability and improve the photoelectric conversion efficiency of solar cells. In this study, the geometry, electronic structure, and optical properties of FA1−xCsxPbI3−yCly were calculated using Cs and Cl co-doped with FAPbI3 using first principles. The analysis revealed that the Goldschmidt factors of the doped system were between 0.962 and 0.974, indicating that the systems could maintain a stable perovskite structure and that the doped system had lower energy and a more stable structure. By calculating the energy bands, it was found that the doped ions have a more pronounced effect on the increase in the dispersion at the bottom of the conduction band than on the decrease in the dispersion at the top of the valence band of the system, and the reduction of the effective mass of carriers is more favorable for transport. As for the optical properties, the right amount of doping is favorable for the improvement of light absorption, whereas excess doping shortens the light absorption range and weakens the light absorption effect, in which FA0.875Cs0.125PbI2.958Cl0.125 has the largest light absorption coefficient. It is shown that the photoelectric properties of FAPbI3 can be effectively modulated by the co-doping with Cs and Cl, which can provide a theoretical reference for the precise preparation of more efficient solar cells.

Performance and structure of Ti-doped amorphous carbon/CrN/Ti multilayer coating deposited on 316L stainless steel for use as bipolar plate in proton exchange membrane fuel cell

In order to improve the corrosion resistance and conductivity of stainless steel bipolar plates, three-layer Ti-doped amorphous carbon/CrN/Ti films were deposited on 316L stainless steel used for bipolar plates in PEMFCs. Titanium as the doped element added into amorphous carbon. Magnetron sputtering technology was used to deposit the films and control the titanium doped content by different titanium target currents. The structure transformation law of Ti content in amorphous carbon coating was studied. The application principle of corrosion resistance and conductivity of bipolar plates during the transformation of the coating structure from amorphous carbon to carbide was analyzed. With increasing Ti-doped content, the sp2/sp3 ratio increased, and the amorphous carbon film gradually transformed to titanium carbide matrix film. Characterization of the electrochemical corrosion confirmed that the anti-corrosion property of the films was closely related to the Ti-C phase and sp2/sp3 ratio. Ti-doped amorphous carbon/CrN/Ti film, which is built at 1A Ti target current, has the best corrosion current density. The interfacial contact resistance (ICR) first decreased and then increased with increasing Ti content. When excessive doping of titanium atoms makes the coating become a TiC matrix, the corrosion resistance and ICR property of the coating worsen. The film’s state of chemical bonds after electrochemical corrosion was tested by XPS to study the ICR increase mechanism. The Ti-doped amorphous carbon/CrN/Ti multilayer film can be used as a modified coating of 316L stainless steel bipolar plates for PEMFCs.

Lattice evolution and microwave dielectric properties of La‐doped yttrium aluminum garnet ceramics

AbstractIn this study, Y3−xLaxAl5O12 (0 ≤ x ≤ 0.09) ceramics were synthesized, and the phase composition, lattice evolution, and microwave dielectric properties were investigated in detail. Scanning electron microscopy confirms that the addition of moderate amounts of La2O3 improves the grain development of YAG ceramics, but excessive doping destabilizes the crystal structure. Transmission electron microscopy characterization shows that the variation of the dielectric properties of the samples with x‐value is related to the occurrence of benign dislocation structures caused by modifications in the type and content of the A‐site rare‐earth ions. The variations in relative density, dielectric constant, and quality factor remain basically coordinated. The optimum microwave dielectric properties of La3+ doped YAG samples are exhibited as εr = 10.61, Q × f = 187, 542 GHz, τf = −31.2 ppm/°C when La2O3 is doped at x = 0.015.

Enhanced sensitivity from Ag micro-flakes encapsulated Ag-doped ZnO nanorods-based UV photodetector

An innovative method of improving zinc oxide (ZnO) nanorods-based ultraviolet (UV) photodetectors was fabricated by photodeposition of silver (Ag) micro-flakes on top of Ag-encapsulated Ag-doped ZnO nanorods. Four concentrations are selected for the doping process (0, 1.7, 3.4, and 5.1 mol%). The Ag-doped ZnO nanorods are synthesized via the hydrothermal method, followed by photodeposition using AgNO3 solution, both of which are low-cost and simple. Ag doping resulted in thinner and shorter ZnO nanorods, improved crystallinity, and reduction of deep-level emissions as corroborated by field emission scanning electron microscopy, X-ray diffraction, and photoluminescence analyses. UV photodetectors fabricated from the samples showed that Ag-doped ZnO nanorods in addition to Ag micro-flakes have improved sensitivity and gain than non-doped ZnO nanorods. Excessive doping results in a higher dark current and reduced sensitivity. A proposed mechanism is given showing the source of photocurrents from Ag micro-flakes and Ag-doped ZnO nanorods.

Nonstoichiometric Salt Intercalation as a Means to Stabilize Alkali Doping of 2D Materials.

Although doping with alkali atoms is a powerful technique for introducing charge carriers into physical systems, the resulting charge-transfer systems are generally not air stable. Here we describe computationally a strategy towards increasing the stability of alkali-doped materials that employs stoichiometrically unbalanced salt crystals with excess cations (which could be deposited during, e.g., insitu gating) to achieve doping levels similar to those attained by pure alkali metal doping. The crystalline interior of the salt crystal acts as a template to stabilize the excess dopant atoms against oxidation and deintercalation, which otherwise would be highly favorable. We characterize this doping method for graphene, NbSe_{2}, and Bi_{2}Se_{3} and its effect on direct-to-indirect band gap transitions, 2D superconductivity, and thermoelectric performance. Salt intercalation should be generally applicable to systems which can accommodate this "ionic crystal" doping (and particularly favorable when geometrical packing constraints favor nonstoichiometry).

Extremely Suppressed Energetic Disorder in a Chemically Doped Conjugated Polymer.

Chemical doping can be used to tune the optoelectronic properties of conjugated polymers (CPs), extending their applications as conducting materials. Unfortunately, chemically doped CP films containing excess dopants exhibit an increase in energetic disorder upon structural alteration, and Coulomb interactions between charge carriers and dopants also affect such disorder. The increase in energetic disorder leads to a broadening of the density of states, which consequently impedes efficient charge transport in chemically doped CPs. However, the molecular origins that are inherently resistant to such incidental increase of energetic disorder in chemically doped CPs have not been sufficiently explored. Here, it is discovered that energetic disorder in chemically doped CPs can be suppressed to a level close to the theoretical limit. Indacenodithiophene-co-benzothiadiazole (IDTBT) doped with triethyloxonium hexachloroantimonate (OA) exhibits disorder-free charge-transport characteristics and band-like transport behavior with astonishing carrier mobility as a result of reinforced 1D intramolecular transport. Molecular structure of IDTBT provides a capability to lower the energetic disorder that generally arises from the inclusion of heterogeneous dopants. The results suggest the possibilities of implementing disorder-free CPs that exhibit excellent charge transport characteristics in the chemically doped state and satisfy a prerequisite for their availability in the industry.

Boosting the thermoelectric performance of GeTe via vacancy control and engineering sintering parameters

Pristine GeTe is a p-type degenerate semiconductor with very low thermoelectric performance due to its large carrier concentration induced by large Ge vacancy. In this work, Ge vacancy was effectively decreased through the melt quenching process and also non-equilibrium reaction caused by the spark plasma sintering (SPS) consolidation. The effects of excess Ge doping were studied on the polycrystalline and single-crystal specimens to understand the excess doping effect on the carrier concentration. The p-type carrier concentration for the Ge 1.03 Te polycrystalline specimen was significantly reduced to 2.43 ×10 20 cm -3 from 8.9 ×10 20 cm -3 of pristine GeTe. This work realized that the zT of the single-crystal specimen was lower than that of pellets prepared by the spark plasma sintering due to its high carrier concentration. Meanwhile, polycrystalline specimen sintered by spark plasma sintering exhibits lower thermal conductivity due to the reduction of carrier concentration and phonon scattering centers such as Ge precipitates and nanostructured defects. We also systematically studied the different SPS sintering conditions on thermoelectric properties of the Ge 1.03 Te polycrystalline specimen. Eventually, superior thermoelectric performance zT =1.8 at 700 K was obtained in 3% Ge excess Ge 1.03 Te polycrystalline specimen sintered at 773 K with 30 MPa pressure. The zT enhancement results from the synergistic contribution of the enhanced Seebeck coefficient by excess Ge doping and reduced thermal conductivity through SPS sintering pressure. This work demonstrates that the zT value of GeTe can be effectively enhanced by adding excess Ge with optimal SPS conditions. Our results provide an enlightening strategy to improve thermoelectric material performance. • Enhanced power factor in Ge excess doping sample. • Reduced the thermal conductivity through microstructure effects as well as Ge precipitates. • Understanding effect of different sintering pressures on thermoelectric properties of GeTe. • A record high ZT of 1.8 at 700 K were successfully realized in Ge 1.03 Te polycrystalline sample. • Comparing the single crystal and polycrystalline samples and studied their thermoelectric properties.

Optimizing electrical and thermal transport properties of Ca3Co4O9 based thermoelectric materials by Ag and Fe co-addition

Ca 3-x Ag x Co 4-y Fe y O 9 (x=0, 0.05; y=0, 0.1, 0.2, 0.4) polycrystalline materials were prepared by sol-gel method with spark plasma sintering. The phase composition, microstructure and high temperature thermoelectric property of the bulk samples were systematically studied. The sintered Ca 3-x Ag x Co 4-y Fe y O 9 ceramics exhibit fine lamellar grain and dense morphology. Compared with single addition of Ag or Fe, appropriate co-additive amount of Ag and Fe can further increase electrical conductivity due to higher carrier concentration and mobility, while decreasing thermal conductivity by stronger phonon scattering. The coordinated regulation of electron and phonon transport is realized in Ca 2.95 Ag 0.05 Co 3.8 Fe 0.2 O 9 with the maximum ZT value of 0.25 at 1000 K, which is 34% larger than that of pure Ca 3 Co 4 O 9 . • Appropriate co-doping content of Ag and Fe in Ca 3 Co 4 O 9 can bring higher carrier concentration and mobility, while enhancing phonon scattering. • Simultaneously enhanced power factor and suppressed thermal conductivity can be achieved by Ag and Fe co-doping with appropriate doping contents. • Excessive doping of Fe would generate secondary phase FeO and deteriorate thermoelectric property.

Effect of excessive doping of Ti on photocatalytic properties of Ti and Ga co-doped ZnO nanopowders

Effect of excessive doping of Ti on photocatalytic properties of Ti and Ga co-doped ZnO nanopowders

Effect of Ho2O3 doping on the microstructure and electrical properties of ZnO–Bi2O3–Sb2O3–Cr2O3–Co2O3–MnO2-based varistors

Ho2O3 doped ZnO–Bi2O3–Sb2O3–Cr2O3–Co2O3–MnO2-based varistors (ZBSCCM based varistors) was fabricated by solid-state reaction and subsequent sintering process. Microstructure characterization by X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicated the Ho2O3 phase with the doping content no more than 0.8 mol% was distributed along the grain boundaries of ZnO grains and could restrain the growth of ZnO grain. However, excessive Ho2O3 doping (>1.0%) delayed the full densification of the green pellets, leading to the decrease in relative density of the sample. The electrical properties were investigated by means of direct current measurement. It was found that proper amount of Ho2O3 doped in the ZBSCCM based varistors was able to improve the electrical properties. Particularly, the varistor doped with 0.8 mol% of Ho2O3 possessed the highest breakdown field (1578.5 V/mm), an excellent nonlinear coefficient α (86.3) and a small leakage current density (1.06 μA/cm2).

Evolution of dynamics of physico-chemical and mechanical properties of hydroxyapatite with fluorine addition and degradation stability of new matrices

This multidisciplinary study examined sensitively the change in the dynamics of main mechanical performance, stability of crystal structure, crystallinity quality, strength, corrosion resistance, biocompatibility, resistance to structural degradation/separations and mechanical durability features of hydroxyapatite (HAp) biomedical materials based on the fluorine addition and degradation process to guide future medical and dental treatment studies. In the study, the fluorine ions were used to be the dental coating, filling and supporting material for biologically or synthetically produced bone minerals. The general characteristic properties were investigated by means of standard spectroscopic, structural and mechanical analysis methods including RAMAN, SEM-EDS, TEM, Vickers micro-indentation hardness and density measurements. A time dependent release test was performed to evaluate possible fluorine ion release after the degradation process. It was found that the fundamental characteristic properties of HAp biomedical materials are noted to improve with the increase in the fluoride level up to 2% due much more stabilization of HAp crystal system. The combination of RAMAN spectra and powder XRD analyzes indicates that 2% addition level affects positively the formation velocity of characteristic HAP phase. Besides, fluorine doped HAp materials all exhibited the main characteristic peaks after degradation process. This is attributed to the fact that the fluorine ions enabled the hydroxyapatite to enhance the structural quality and stability towards the corrosion environment. However, in case of excess dopant level of 3% the degradation rates were obtained to increase due to higher contribution rate and especially electrostatic interactions. As for the surface morphology examinations, 2% fluorine added HAp with the highest density of 3.0879 g/cm3 was determined to present the superior crystallinity quality (smallest grain size, best smooth surface, honeycomb pattern, regular shaped particles and densest particle distributions through the specimen surface). Conversely, the excess fluorine triggered to increase seriously degree of micro/macro porosity in the surface morphology and microscopic structural problems in the crystal system. Thus, the HAp doped with 3% was the most affected material from the degradation process. Additionally, the fluorine ion values read after the release process were quite far from the value that could cause toxic effects. Lastly, the optimum fluorine addition provides the positive effects on the highest durability, stiffness and mechanical fracture strength properties as a consequence of differentiation in the surface residual compressive stress regions (lattice strain fields), amplification sites and active operable slip systems in the matrix. Hence, the crack propagations prefer to proceed in the transcrystalline regions rather than the intergranular parts. Similarly, it was found that Vickers micro-indentation hardness tests showed that the microhardness parameters increased after the degradation process. All in all, the fluorine addition level of 2% was noted to be good choice to improve the fundamental characteristic properties of hydroxyapatite biomedical materials for heavy-duty musculoskeletal, orthopedic implant, biological and therapeutic applications in medicine and dentistry application fields.

Analysis of complex impedance and electrical conductivity of YCr0.5Mn0.5O3–CaCu3Ti4O12 negative temperature coefficient ceramics

YCr 0.5 Mn 0.5 O 3 (YCM)-CaCu 3 Ti 4 O 12 (CCTO) ceramics were prepared using a solid processing method, and their properties were studied. XRD measurements showed that all prepared ceramics had pure perovskite structures. With increasing YCM content, grain size in ceramics decreased, and the resistivity of materials was found to be very sensitive to grain size and grain size distribution. Moreover, ceramics had NTC characteristics, and values of ρ 25 , B 25/75 , and E a ranged from 2.21 × 10 6 –7.30 × 10 6 Ω cm, 5797–6300 K, and 0.5390–0.5800 eV, respectively. The presence of heterovalent ion pairs in samples suggested that conduction mechanism may have been related to electron hopping. Impedance spectroscopy results showed that excessive doping with YCM resulted in greater contribution from grains to overall resistance of the material. Temperature-dependent electrical relaxation behavior was dominated by short-range movement of charge carriers.

Efficient ammonia synthesis over Ru/CeO2-PrOx catalysts with controlled Ru dispersion by Ru-Pr interaction

Ru/CeO2-PrOx catalysts for NH3 synthesis were prepared using the urea-based homogeneous co-precipitation method, and the effect of Pr-doped CeO2 support on the catalytic activity was investigated. An optimal range of Pr content (25–75 %) improved NH3 synthesis activity. CO pulse adsorption and operando X-ray absorption fine structure (XAFS) measurements revealed that the increase in NH3 synthesis activity was due to the improvement in Ru dispersion by the interaction between PrOx and Ru, rather than the generally discussed Ce3+/Ce4+ ratio. However, excess Pr doping prevented the Ru reduction and formation of active sites. In this Ru/CeO2-PrOx catalyst system, the activity is governed by the number of active sites that can be controlled by the Pr content. In the high-pressure evaluation (5 MPaG), the NH3 synthesis rate of the Ru/CeO2-PrOx catalyst (Ce/Pr = 1) was 9.0 mmol g-1h−1, which is 1.4 times higher than that of the Ru/CeO2 catalyst.

Reverse Conversion Treatment of Gaseous Sulfur Trioxide Using Metastable Sulfides from Sulfur-Rich Flue Gas.

Sulfur trioxide (SO3) is an unstable pollutant, and its removal from the gas phase of industrial flue gas remains a significant challenge. Herein, we propose a reverse conversion treatment (RCT) strategy to reduce S(VI) in SO3 to S(IV) by combining bench-scale experiments and theoretical studies. We first demonstrated that metastable sulfides can break the S-O bond in SO3, leading to the re-formation of sulfur dioxide (SO2). The RCT performance varied between mono- and binary-metal sulfides, and metastable CuS had a high SO3 conversion efficiency in the temperature range of 200-300 °C. Accordingly, the introduction of selenium (Se) lowered the electronegativity of the CuS host and enhanced its reducibility to SO3. Among the CuSe1-xSx composites, CuSe0.3S0.7 was the optimal RCT material and reached a SO2 yield of 6.25 mmol/g in 120 min. The low-valence state of selenium (Se2-/Se1-) exhibited a higher reduction activity for SO3 than did S2-/S1-; however, excessive Se doping degraded the SO3 conversion owing to the re-oxidation of SO2 by the generated SeO32-. The density functional theory calculations verified the stronger SO3 adsorption performance (Eads = -2.76 eV) and lower S-O bond breaking energy (Ea = 1.34 eV) over CuSe0.3S0.7 compared to those over CuS and CuSe. Thus, CuSe1-xSx can serve as a model material and the RCT strategy can make use of field temperature conditions in nonferrous smelters for SO3 emission control.

Experimental and DFT studies of flower-like Ni-doped Mo2C on carbon fiber paper: A highly efficient and robust HER electrocatalyst modulated by Ni(NO3)2 concentration

Developing highly efficient and stable non-precious metal catalysts for water splitting is urgently required. In this work, we report a facile one-step molten salt method for the preparation of self-supporting Ni-doped Mo2C on carbon fiber paper (Ni-Mo2CCB/CFP) for hydrogen evolution reaction (HER). The effects of nickel nitrate concentration on the phase composition, morphology, and electrocatalytic HER performance of Ni-doped Mo2C@CFP electrocatalysts was investigated. With the continuous increase of Ni(NO3)2 concentration, the morphology of Mo2C gradually changes from granular to flower-like, providing larger specific surface area and more active sites. Doping nickel (Ni) into the crystal lattice of Mo2C largely reduces the impedance of the electrocatalysts and enhances their electrocatalytic activity. The as-developed Mo2C-3 M Ni(NO3)2/CFP electrocatalyst exhibits high catalytic activity with a small overpotential of 56 mV at a current density of 10 mA·cm−2. This catalyst has a fast HER kinetics, as demonstrated by a very small Tafel slope of 27.4 mV·dec−1, and persistent long-term stability. A further higher Ni concentration had an adverse effect on the electrocatalytic performance. Density functional theory (DFT) calculations further verified the experimental results. Ni doping could reduce the binding energy of Mo-H, facilitating the desorption of the adsorbed hydrogen (Hads) on the surface, thereby improving the intrinsic catalytic activity of Ni-doped Mo2C-based catalysts. Nevertheless, excessive Ni doping would inhibit the catalytic activity of the electrocatalysts. This work not only provides a simple strategy for the facile preparation of non-precious metal electrocatalysts with high catalytic activity, but also unveils the influence mechanism of the Ni doping concentration on the HER performance of the electrocatalysts from the theoretical perspective.

Excess dopant effect in platinum‐based alloys toward the oxygen electroreduction reaction

AbstractDoping the PtNi octahedra with trace amount of transition metals has recently been shown to significantly improve the activity and durability of the oxygen reduction reaction (ORR). However, the role of excessive amounts of doped elements on ORR performance is unclear. In this work, PtNi octahedra were synthesized with and without excess Mo dopant. Also, spherical PtNi nanoparticles containing excess Co dopant were synthesized. The ORR performance revealed that PtNiMo octahedra and PtNiCo nanoparticles showed inferior ORR activities compared to bimetallic PtNi octahedra. Based on the electrochemical analysis, we found that unfavorable oxygen‐binding strengths of PtNiMo and PtNiCo catalysts decrease the ORR performances.

Effect of alkali earth metal doping on the CuO/Al2O3 oxygen carrier agglomeration resistance during chemical looping combustion

The influence of alkali earth metals (AEMs, including Ca, Sr and Ba) doping on the performance of CuO/Al2O3 oxygen carrier (OC) in chemical looping combustion (CLC) was investigated. The OCs using solid-state synthesis method were evaluated in a fluidized bed reactor using municipal solid waste (MSW) syngas as fuel for 50 redox cycles. It was found that the doping of AEMs enhanced the CLC performance on CuO/Al2O3. XRD characterization and TGA analysis showed that aluminates of AEMs were formed in the doped OCs leading to the segregation of CuO from CuAl2O4 spinel, thereby promoting the redox kinetics. The OCs doped with AEMs exhibited enhanced stability and agglomeration resistance throughout multiple redox cycles in the fluidized bed experiments. CuO/Al2O3 containing 40 wt% CuO suffered from severe agglomeration and deactivation during initial 5 cycles, while the OCs with Ba, Sr and Ca doping respectively deferred the agglomeration to 15-20th, 20-25th and >50th cycle. 5–10 wt% Ca-doping content exhibited great stability without deactivation or agglomeration issues during 50 cycles, but excess Ca doping (≥20 wt%) showed severe agglomeration. The agglomeration was attributed to the outward migration of Cu/CuO, leading to the segregation from CuAl2O4 and surface enrichment. The enhanced agglomeration resistance with AEM doping was mainly attributed to outward migration of AEM species and inward migration of Cu species during the synthesis process.

Anomalous high-temperature quasi-linear superelasticity of Ni-Fe-Ga-Co shape memory alloy

The superelasticity of shape memory alloys is associated with the martensitic transformation which has been widely used in engineering applications. Here, we clarify quasi-linear superelasticity in Ni-Fe-Ga-Co shape memory alloy exhibiting a recovery strain of 3.58% at 573 K, which is far above the martensitic transformation temperature. Real-time in-situ neutron diffraction measurement was used to explore the underlying quasi-linear superelasticity mechanism via tracing the structural evolution during cyclic compression loading. Neutron diffraction observation showed that the superelasticity is correlated with stress-induced continuous variation of lattice parameter. The in-situ neutron diffraction provides the direct evidence on the anomalous diffraction peak width broadening, which mainly stems from the spatial heterogeneity in strain. The excessive Co doping is responsible for the decrease in stacking-fault energy leading to an increase in stacking faults, which suppresses the martensitic transformation and triggers the nucleation of the weak first-order phase under the external stress. The study provides insights into the interplay between superelasticity and structural transformation in shape memory alloys, and it is also instructive for understanding the anomalous high-temperature quasi-linear superelasticity in functional materials. • The quasi-linear superelasticy of Ni-Fe-Ga-Co shape memory alloy is caused by the weak first-order transformation. • The quasi-linear superelasticity of Ni-Fe-Ga-Co exhibits a recovery strain of ~3.58% at 573 K, which is rarely reported. • The excessive Co is account for trigger the nucleation of the weak first-order phase under the external stress.

Enhanced thermoelectric performance of n-type polycrystalline SnSe via NdCl3 doping

A series of n-type polycrystalline SnSe0.95 - xmol% NdCl3 samples were synthesized using the melting method combined with spark plasma sintering (SPS). Doping NdCl3 significantly improves the electrical conductivity and suppresses the deterioration of the Seebeck coefficient after thermal excitation, which leads to significantly higher power factors than SnSe0.95. In addition, excessive doping of NdCl3 not only introduces a large number of point defects but also produces NdCl3 precipitates, which largely enhances the phonon scattering and significantly reduces the thermal conductivity. As a result, a maximum ZT value of 1.3 at 773 K has been obtained in SnSe0.95 - 1.5 mol% NdCl3 sample, indicating that the doping of rare earth halides can effectively enhance the thermoelectric performance of n-type SnSe0.95 by simultaneously improving the power factor and reducing the lattice thermal conductivity.

Ni(NO3)2-induced high electrocatalytic hydrogen evolution performance of self-supported fold-like WC coating on carbon fiber paper prepared through molten salt method

Exploring high-performance and inexpensive electrocatalysts for hydrogen evolution reaction to substitute Pt-based compounds is important to sustain hydrogen production. Herein, WC based self-supported catalysts doped with different concentration of nickel nitrate solution (Ni(NO3)2) were synthesized on carbon fiber paper (CFP) by one-step molten salt method (abbreviated as x Ni-WC@CFP). With the increasing of Ni(NO3)2 concentration, fold-like structures were formed on the catalysts, which was conducive to active sites exposure. As Ni(NO3)2 concentration increased from 1M to 5M, the catalytic performance of the electrocatalyst showed a trend of increasing first and then decreasing. The optimal 4M Ni-WC@CFP showed comparable catalytic ability in 0.5M H2SO4 with a low overpotential of 73 mV at 10 mA cm−2 and Tafel slope of 66.4 mV dec−1. However, excessive nickel doping would inhibit HER performance. The density functional theory calculation further verified the experimental results. The adsorption energy of hydrogen showed a decreasing trend with the rising amount of Ni doped in, while the W-H binding energy would change in an opposite direction as over doped Ni. This work provided an insight for the preparation of high-efficiency self-supported W-based electrocatalysts and expounded the influence trend of Ni doping concentration on the performance of electrocatalysts.