Ni-doped TiO2 Research Articles

Achieving superior hydrogen sorption kinetics of MgH2 by addition of Ni-doped TiO2 catalysts

MgH2 is a high-density hydrogen storage material but requires an efficient catalyst to improve its poor kinetics and reduce high operating temperature. TiO2 is a widely used photocatalyst for water splitting and hydrogen production, and has also demonstrated catalytic ability in the gas-solid reaction of MgH2. In this study, we synthesize the Ni-doped TiO2 nanoparticles, which significantly reduce the hydrogen absorption temperature down to subzero temperatures. The milled composite of MgH2 with 10 wt% Ti(5Ni)O2 can absorb 5.25 wt% H2 within 30 s at 25 °C, 4.30 wt% H2 within 50 s at 0 °C, and 3.94 wt% H2 within 50 s even at a low temperature of −30 °C. This composite can release 6.04 wt% of hydrogen in 3 min at 250 °C, and the dehydrogenation activation energy is reduced to 74.57±1.36 kJ/mol, a notable reduction in comparison to that observed in pure MgH2. This study demonstrates the potential of the modified TiO2 as an important kind of catalyst for solid-state hydrogen storage materials.

Role of outer shell electron-nuclear distant of transition metal atoms (TMA) on band gap reduction and optical properties of TiO2 semiconductor

The reduction of the band gap of titanium dioxide (TiO2) via transition metal atoms (TMAs) is the focus of many research groups to increase its absorption to visible region of electromagnetic (EM) radiation. In this modeling it was shown that atoms having near outer electron shells affect strongly on the band gap of TiO2. The TiO2 has exceptional photoactivity, high stability, and cost-effectiveness. The results of the current study emphasized that adjustable TiO2 photocatalyst material can be produced through band gap reduction by Pt, Pd, and Ni dopants. The electronic configurations and optical properties of both undoped and (Ni, Pd and Pt)-doped TiO2 have been studied using first-principles calculations within the framework of Density Functional Theory (DFT) with the aid of the Vienna Ab initio Simulation Package (VASP). The role of electronegativity of TMAs on band gap drop was discussed for the first time. The band gap of clean TiO2 was found to be 3.2 eV using the band structure (BS) and Tauq model. The results indicate that Ni TMA with lowest electronegativity reduces the band gap of TiO2 to the lowest value (0.86 eV). The results of BS and density of state revealed the fact that small outer shell electron-nuclear distant TMA more affected the band gap of TiO2. The band gap determined from the imaginary part of the optical dielectric function closely aligns with those determined from the BS diagram. The increase in the refractive index (n) was observed with the increase of Ni, Pd, and Pt into the TiO2 structure, which indicates an increase in charge density within the TiO2 structure. The reflectance, absorbance, and transmittance results suggest that Pd and Pt-doped TiO2 are responsive to the visible region of electromagnetic radiation, whereas Ni-doped TiO2 exhibits responsiveness in the IR region. In its pure state; TiO2 was found almost transparent in the visible and IR regions of EM radiation.

Enhanced photo-electro catalytic CO2 conversion using transition metal doped TiO2 nanoparticles

The Fe, Co, and Ni-doped TiO2 were synthesised by sol–gel process, and the nanomaterials were coated on electrodes through a slurry with Nafion. This study aims to use prepared nanoparticles of Fe, Co, and Ni-doped TiO2 to enhance the photo-electrocatalytic conversion of CO2. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), and electrochemical analyses were utilized to characterise the doped and undoped TiO2 nanoparticles. Transmission electron microscopy (TEM) studies revealed that the nanomaterials had an average size below 20 nm. Tauc plot analysis for optical absorption studies shown a reduction in band gap when doped with Fe, Co and Ni, with the most significant decrease observed for Fe-doped TiO2, following the order Fe < Co < Ni. Electrochemical CO2 conversion efficiencies were investigated through cyclic voltammetry (CV) curves, electrochemical impedance spectroscopy (ESI), and linear sweep voltammetry (LSV) studies. The results were analysed based on various scan rates and photo exposure, indicating superior performance for Fe-TiO2, aligning with the observed band gap trends. Gas chromatography (GC) analysis of the reduction products revealed the generation of hydrocarbons, with Fe-TiO2 exhibiting the most favourable outcomes. This research provides valuable insights into tailoring TiO2 nanoparticles for efficient photo-electro catalytic reduction of CO2.

Looking into how nickel doping affects the structure, morphology, and optical properties of TiO2 nanofibers

In this paper, we have systematically studied the structural, morphological, and optical properties of Ni-doped TiO2, synthesized via a simple, cost-effective electrospinning method followed by calcination at 500 °C. The nanofibers with a core-shell structure were relatively homogeneous, smooth and randomly oriented, and there were no significant differences in fiber diameters due to Ni2+ content. Core loss mapping using electron energy loss spectroscopy confirmed an even distribution of titanium and relatively uniform nickel in the fibers. It was found that doping with 0.5 mol.% Ni2+ decreased the rutile content, while doping with 1 mol.% Ni2+resulted in a pure anatase phase with a significantly increased specific surface area (36.6 m2/g). Further increase in Ni2+ content (3–10 mol.%) not only prolonged the response of TiO2 nanofibers to visible light, but also increased the specific surface area (49.5 m2/g), decreased crystallite size (7 nm), and increased rutile content in TiO2 (33 wt.%). Photoluminescence analysis revealed that doping TiO2 with different amounts of Ni2+ leads to a gradual decrease of emission spectra intensity and red shift in the maxima positions. The XPS results confirmed that as the Ni2+ content enlarged, the Ti2+ and Ti3+ content increased significantly, effectively promoting the formation of oxygen vacancies. Raman analysis showed that an increase in nickel content (3–5 mol.%) led to a decrease and shift in peak intensity due to Ti3+ formation and also the possible presence of NiTiO3 phases. HRTEM analysis showed that Ni was doped into the substitution sites of both the anatase and rutile TiO2 lattice but had a stronger influence on the distortion of the anatase phase. The photocatalytic activity of Ni-doped TiO2 nanofibers was explored by analyzing the degradation of an antibiotic, oxytetracycline, monitored in laboratory conditions under visible light irradiation. After 60 min of irradiation, the degradation of OTC with 1Ni-TiO2 reached 76.4 % and with 10Ni-TiO2 70.5 %.

Preparation, characterization of co-Ni co-doped titania photocatalyst and its application for the photocatalytic degradation of textile and PPCPs industrial wastewater under sunlight

The undoped TiO2 (T), 1% Ni-doped TiO2 (N1T), and 1% Co–1% Ni co-doped TiO2 (C1N1T) photocatalysts were prepared by the sol–gel technique. The characterization of prepared materials was carried out by X-ray diffraction, Diffused Reflectance Spectroscopy, Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy, Brunauer–Emmett–Teller and Thermogravimetric Analysis to analyze composition, phase, morphology, and optical properties. These results revealed that C1N1T exhibited higher surface area, better pore volume and enhanced optical properties as compared to undoped and Ni-doped TiO2. Furthermore, the photoactivity of C1N1T nanoparticles was manifested toward Acetaminophen, Phenol and reactive dyes i.e., Remazol Black B and Yellow 2 G. Moreover, C1N1T nanoparticles showed remarkable degradation efficiency of 53%, 56%, 98% and 89% for Acetaminophen, Phenol and anionic dyes, i.e. Remazol Black B and Yellow 2 G under optimized conditions (pollutant concentration = 20 ppm; time = 120 min; C1N1T loading = 20 mg; irradiation source = solar light; pH = 4 for each dye, pH = 7 for phenol and pH = 9 for acetaminophen). The significant degradation values suggested that the C1N1T photocatalyst can be effectively employed to degrade the textile dyes and PPCPs from industrial wastewater.

Synthesis, characterization, and photodegradation assessment of Ni and Cd-doped TiO2 nanocrystals via sol-gel method for methylene blue under sunlight

Pristine TiO2, Ni-doped, and Cd-doped TiO2 nanocrystals were successfully synthesized by utilizing a single-step sol-gel process. The average particle size (D) of pristine TiO2 was found to be 10.64 nm, while with the addition of Cd and Ni content (0.1) w%, the crystallite size steadily dropped to (10.39 to 8.44) nm. The band gap energies of (0.1) w% Cd and nickel-doped TiO2 are determined (3.20 and 3.07) eV, respectively, which are smaller than that of 3.29 eV for the pristine TiO2. The assessment of the photosensitive activity under visible light irradiation was conducted using the Methylene blue (MB) degradation rate.

Degradation of textiles dyes and scavenging activity of spherical shape obtained anatase phase of Co–Ni-doped TiO2 nanocatalyst

Degradation of textiles dyes and scavenging activity of spherical shape obtained anatase phase of Co–Ni-doped TiO2 nanocatalyst

A novel paper-based electrochemical device modified with Ni-doped TiO2 nanocrystals-decorated graphene oxide for ascorbic acid detection

This study presents the development of a novel paper-based electrochemical device modified with pure and nickel-doped TiO2 nanocrystals and graphene oxide to enhance its ability to detect ascorbic acid (AA). The use of nanomaterials in the fabrication of the sensor provides a high surface area-to-volume ratio, leading to an increase in the sensitivity and selectivity of the device. The nanomaterials were synthesized, and a combination with the best properties was selected for detecting AA. The morphological, structural, and electrical properties of the nanomaterials in the paper device were investigated using scanning electron microscopy (SEM), Raman spectroscopy (Raman), and cyclic voltammetry (CV), respectively. The sensor's performance was evaluated through various experiments, including cyclic voltammetry, to measure its sensitivity and selectivity in detecting AA. The results indicate that adding Ni-doped TiO2 nanocrystals improves the sensor's sensitivity while incorporating graphene oxide enhances its selectivity. Furthermore, the sensor's performance was compared to that of other commonly used sensors, and it was found to be highly sensitive and selective. Therefore, this paper-based electrochemical sensor, modified with nanomaterials, shows great potential for detecting AA and other applications, such as environmental monitoring and medical diagnostics, due to its high sensitivity and selectivity, low cost, and ease of use.

Synthesis of Ni-Doped TiO2 Microtubes as Cathode Catalyst for Rechargeable Li-O2 Batteries

Rechargeable nonaqueous Li-O2 batteries are considered as one of the most promising energy storage systems due to their super-high theoretical energy density. However, some technical obstacles, such as high overpotential and poor cycle stability, need to be overcome urgently, so that it is possible to make Li-O2 batteries commercially viable. The key is to develop effective bifunctional cathode catalysts. Herein, Ni-doped TiO2 (Ni-TiO[Formula: see text] with microtubule structure was prepared by hydrothermal method and used as the cathode catalyst of Li-O2 batteries. At a current density of 100[Formula: see text]mA[Formula: see text]g[Formula: see text], Li-O2 batteries with Ni-TiO2 catalysts showed an initial discharge capacity of 5100[Formula: see text]mAh g[Formula: see text] and can maintain 52 stable cycles at 100[Formula: see text]mA[Formula: see text]g[Formula: see text] with a fixed capacity of 500[Formula: see text]mAh[Formula: see text]g[Formula: see text]. The microtubule structure composed of nanosheets not only facilitates the diffusion of O2 and electrolyte, but also provides abundant catalytic sites for oxygen reduction reactions and oxygen evolution reactions (ORR/OER). In addition, the Ni doping into the structure of TiO2 can significantly enhance the catalytic activity of ORR/OER, resulting in a reduced discharge/charge overpotential and enhanced discharge-specific capacity.

Ni-doped TiO2 supported Pt single-atom catalyst for partial oxidation of ethylene glycol to high-value chemicals in alkaline media

Pt-based electrocatalysts are usually used in several catalytic reactions. However, its high cost, scarcity, and susceptibility towards poisonous intermediate species highly limit these catalysts' large-scale applications. Downsizing catalysts to single-atom scale (SAC) have fascinated extensive research interests due to their higher activity, selectivity, and stability. Herein, we prepared highly active, selective, and poisoning-tolerant PtSACs on Ni-doped TiO2 support (PtSAC-Ni0.1Ti0.9O2). Ni in the catalyst creates a suitable environment to adsorb more OH− and make Pt accessible and ready for further oxidations. Thus, it exhibits higher electrocatalytic performance towards EGO than PtSAC-TiO2 does. It is also by far better than PtNP– Ni0.1Ti0.9O2. The higher catalytic performance by PtSAC-Ni0.1Ti0.9O2 is due to the synergistic effects of Ni and Pt. The catalyst selectively produces glycolate, formate, and hydrogen. Glycolate and formate are high-value chemicals for domestic uses or as inputs for industries to produce other chemicals. The catalyst also shows excellent Faradaic efficiency (>98 %) and stability towards EGO in alkaline media. The strong metal-support interactions between the catalyst and the support retard the agglomeration of the single atoms, thereby increasing their stability.

Theoretical and experimental studies on electronic structure and optical properties of NixTi1-xO2

The effects of Ni-doping on the electronic structure and optical properties of TiO2 were studied. Ni-doping can promote the transformation of rutile to anatase. With the increase of Ni-doping, the band gap gradually decreases and the absorption band edge gradually shifts to the long-wave direction. The energy band structure, electronic density of states and optical properties of Ni-doped TiO2 were investigated using a first-principles plane-wave pseudopotential method based on the framework of density-functional theory (DFT). With the increase of Ni-doping, the band gap of TiO2 gradually decreases. The results of optical properties study is consistent with the experimental results.

Use of nickel-electroplating wastewater to synthesize Ni-doped TiO2 and NiTiO3 coatings by plasma electrolytic oxidation to treat hexavalent chromium in real electroplating wastewater

The use of residual water from nickel plating for the synthesis of Ni/TiO2 coatings using the PEO technique was carried out in this work. Evaluation by response surface methodology (RSM) for the studied coatings in the reduction of Cr(VI) present in chrome-plating wastewater is presented. Duty cycle variations between 2 % and 50 % on Ti substrates of 20 × 20 × 1 mm was employed to obtain the studied coatings. The coatings were characterized by XRD, AFM, SEM/EDS, XPS, and DRS, and computational analysis using DFT was performed. A strong dependence of the duty cycle on the anatase/rutile relation, surface roughness, and Ni incorporation in the coatings is showed. The sample obtained at 50 % of the duty cycle, in addition to the anatase and rutile phase, showed the formation of NiTiO3. Additionally, the incorporation of Ni in Ti sites in TiO2 as a consequence of the d orbitals of Ni, which generated a shift of the absorption band towards the visible and a decrease in the bandgap, is observed. The response surfaces obtained for the reduction of Cr(VI) in the samples of 2 % and 50 % of duty cycle, indicating that the voltage and the concentration of Cr(VI) are the variables with the greatest influence in the process, being the 2 % sample the one that presented the best performance in the photoelectrocatalysis process. In this sense, the optimal conditions for the 2 % sample were determined. Furthermore, the kinetic study to a pseudo-first order kinetic model was adjusted, and the efficiency of the material after 16 cycles of reuse is greater than ∼ 99.4 % in 10 min. Taking advantage of industrial wastewater as a resource using the PEO technique has potential applications in contributing to environmental sustainability.

Co- and Ni-Doped TiO2 Nanoparticles Supported on Zeolite Y with Photocatalytic Properties.

Zeolite Y samples with microporous and hierarchical structures containing Ti-Ni and Ti-Co oxides were obtained as active photocatalysts. Different Ti amounts (5, 10% TiO2) were supported, followed by the loading of Ni or Co oxides (5%). X-ray diffraction evidenced the presence of TiO2 as an anatase. N2 adsorption-desorption results showed type IV isotherms for hierarchical zeolite Y samples, and a combination of type IV and I isotherms for zeolite Y samples. UV-Vis diffuse reflectance spectra showed a shift in the absorption band to visible with increasing Ti loading and especially after Co and Ni addition. A significant effect of the support was evidenced for Ti and its interaction with Co/Ni species. The zeolite Y support stabilized Ti in the 4+ oxidation state while hierarchical zeolite Y support favored the formation of Ti3+ species, Ni0 and Ni2+ and the oxidation of Co to 3+ oxidation state. Photocatalytic activity, under UV and visible light irradiation, was evaluated by the degradation of amoxicillin, used as a model test. The photocatalytic mechanism was investigated using ethanol, p-benzoquinone and KI as ·OH and ·O2- radicals and hole (h+) scavengers. The best results were obtained for the immobilized Ni-Ti species on the hierarchical zeolite Y support.

The Superiority of TiO2 Supported on Nickel Foam over Ni-Doped TiO2 in the Photothermal Decomposition of Acetaldehyde.

Acetaldehyde decomposition was performed under heating at a temperature range of 25-125 °C and UV irradiation on TiO2 doped by metallic Ni powder and TiO2 supported on nickel foam. The process was carried out in a high-temperature reaction chamber, "The Praying MantisTM", with simultaneous in situ FTIR measurements and UV irradiation. Ni powder was added to TiO2 in the quantity of 0.5 to 5.0 wt%. The photothermal measurements of acetaldehyde decomposition indicated that the highest yield of acetaldehyde conversion on TiO2 and UV irradiation was obtained at 75 °C. The doping of nickel to TiO2 did not increase its photocatalytic activity. Contrary to that, the application of nickel foam as a support for TiO2 appeared to be highly advantageous because it increased the decomposition of acetaldehyde from 31 to 52% at 25 °C, and then to 85% at 100 °C in comparison with TiO2 itself. At the same time, the mineralization of acetaldehyde to CO2 doubled in the presence of nickel foam. However, oxidized nickel foam used as support for TiO2 was detrimental. Most likely, different mechanisms of electron transfer between Ni-TiO2 and NiO-TiO2 occurred. The application of nickel foam greatly enhanced the separation of free carriers in TiO2. As a consequence, high yields from the photocatalytic reactions were obtained.

A facile impregnation synthesis of Ni-doped TiO2 nanomaterials for dye-sensitized solar cells

This study reports a facile impregnation method for synthesizing Ni-doped TiO2 nanomaterials using P25-TiO2 as a starting material. The as prepared nanomaterials were subjected to structural and optical characterizations and subsequently employed in photovoltaic studies. X-ray diffraction (XRD) and Raman studies confirmed that Ni doping did not alter the anatase and rutile contents of P25-TiO2. Also, the presence of the constituent dopants and their ionic states were confirmed by Energy-Dispersive X-ray (EDX) and X-ray photoelectron (XPS) spectroscopies. Topographic Atomic Force Microscopic (AFM) images illustrated that Ni doping had increased the surface roughness of the TiO2. Optical characterization by UV-Visible spectroscopy revealed that the Ni doping had caused red shift in light absorption due to reduced TiO2 bandgap and improved the dye adsorption on TiO2 films. Then, the photocurrent–photovoltage property of the fabricated devices was investigated and the optimized 0.10 wt% Ni-doped TiO2 photoanode based device exhibited pronounced power conversion efficiency (PCE) of 6.29% under air mass (AM) 1.5 conditions (100 mWcm−2, 1 sun). Improved charge transport properties were also observed by the electrochemical impedance spectroscopic (EIS) study for the device with optimized Ni-doped TiO2 compared to the control device.

Synthesis of Ni doped-TiO2 Thin Film Photocatalysts on Glass Surfaces

Thin film of TiO2 modified Ni2+ cationic (Ni doped-TiO2) thin films were synthesized from titanium tetraisopropoxide (TTIP) and Ni(NO3)2.6H2O using the combined sol-gel and dip coating method followed by calcination at 500oC for an hour. This study aims to determine the concentration of Ni2+ and the optimum number of layers for application as self-cleaning. Frontier transform infrared (FTIR) spectrophotometric analysis observed a shift in the vibration absorption peak of Ti-O towards a smaller wave number as an indication that the Ni2+ cationic have incorporated in the TiO2matrix in forming Ni-TiO2. Based on the of x-ray diffraction (XRD) it is known that Ni-TiO2 has anatase crystalline phase with a crystallite size of 149.20 nm. Diffuse reflectance ultraviolet-visible (DRSUV-Vis) spectrophotometry showed a decrease in the bandgap energy (3.2 eV to 2.22 eV). Surface morphological by scanning electron microscopy (SEM) method showed that the addition of polyethylene glycol (PEG) resulted in a more homogeneous distribution of particles than thin films without PEG. The self-cleaning activity of Ni-TiO2 was tested for surface hydrophilic properties by measuring the contact angle of water and oil droplets under visible light illumination.

First principles study of optical properties of Ni- and Pd-doped TiO2 as visible light catalyst

Doping TiO2 with noble metals, transition metals, cations, anions have yielded very promising results in enhancing photocatalytic activity of TiO2 in the visible region and its role in generating alternate forms of energy. Noble metals in general can effectively slow down carrier recombination. However, the study of Pd and Ni as dopant can lead to a reliable and versatile TiO2-modified photocatalyst. In this paper, we explore the optical properties of Pd- and Ni-doped TiO2 by doping with 4.17% Ni and Pd dopant concentrations. The optical properties prove that Ni-doped TiO2 can absorb well in the visible region with an absorption coefficient of 1 × 105 cm−1. Hence, Ni-doped TiO2 can successfully alter the electronic and optical properties of TiO2 for favorable future applications. In the visible region, absorption coefficient of Pd-doped TiO2 supercell is around 1.2 × 105 cm−1 which is comparatively greater than that of pure TiO2 confirming its utility as a versatile and viable visible light photocatalyst. The other optical properties like reflectivity, refractivity, extinction coefficient and electron energy loss spectrum have also been studied.

Study of the Photocatalytic Properties of Ni-Doped Nanotubular Titanium Oxide

Nanotubular titanium oxide is widely known as a prospective semiconductor photocatalyst for the process of water splitting. Its photoelectrochemical (PEC) efficiency can be improved by doping with 3d metal. In this work, the synthesis of nanotubular titanium oxide (NTO) was carried out by anodizing titanium substrates using two doping techniques. First, Ni-doped TiO2 was obtained by immersion in Ni salt solution; second, an ethylene glycol-based fluoride electrolyte containing Ni2+ ions solution was used. The obtained samples were analyzed using SEM, XRD, and photoelectrochemical methods. The produced Ni-doped NTO exhibited photocatalytic activity twice as high as that of nondoped NTO. Additionally, it was found that the immersion technique initiated a shift of the incident photon to converted electron (IPCE) spectra to the visible part of the spectrum.

Ni-doped hybrids of TiO2 and two-dimensional Ti3C2 MXene for enhanced photocatalytic performance

Transition metal ion doping is an effective strategy by which to enhance the photocatalytic activity of semiconductor materials. Herein, Ni-doped TiO 2 /Ti 3 C 2 photocatalysts were designed and fabricated using a simple dipping method and their catalytic performance was verified via the degradation of rhodamine B (RhB). Ni doping induces the formation of a defect energy level in TiO 2 , which shortens the transition distance of photogenerated electrons. Ti 3 C 2 acts as a hole acceptor, which is conducive to the transfer of photogenerated charge. The results show that the Ni-doped TiO 2 /Ti 3 C 2 heterojunction structure exhibits the lowest photoluminescence peak intensity, the highest instantaneous current, and excellent photocatalytic performance compared to TiO 2 /Ti 3 C 2 and TiO 2 . At optimal Ni content, the removal efficiency of RhB is 90%, around 3.7 times higher than that of pure TiO 2 . This work details the preparation of an excellent Ni-doped heterojunction structure for enhanced photocatalytic performance, demonstrating an effective strategy by which to improve the charge separation ability. • Ni-doped hybrids of TiO 2 and Ti 3 C 2 MXene structure was prepared for enhanced photocatalytic performance. • The charge separation ability of TiO 2 was enhanced due to the doping of Ni and the coupling of co-catalyst Ti 3 C 2 . • The removal efficiency of RhB by Ni–TiO 2 /Ti 3 C 2 was 3.7 times higher than that of pure TiO 2 .

Synergistic material modification-induced optimization of interfacial charge transfer and surface hydrogen adsorption.

Being chemically stable, low cost and made from abundant resources, titanium dioxide (TiO2) possesses the most desired advantages for photocatalytic applications. However, the intrinsic limits of high surface hydrogen adsorption energy, wide band gap, low separation rate and rapid recombination of the photogenerated charge carriers greatly hamper its utilization. To address these issues, the present work combines density functional theory (DFT) calculations with rational modifications of TiO2 with nickel doping and an ultra-thin shield of fluorinated carbon (FNT) for application in the photocatalytic hydrogen evolution reaction (HER). Comprehensive studies imply that the synergistic modifications not only optimize the surface H adsorption, but also facilitate the interfacial charge transfer and simultaneously prevent the photochemical and chemical corrosion of the catalysts. In good agreement with the theoretical predictions, the resulting FNT photocatalysts demonstrate an optimal HER efficiency of 13.0 mmol g-1 h-1, nearly 33-times and over three-times beyond that of the pristine TiO2 (0.4 mmol g-1 h-1) and the Ni-doped TiO2 (4.2 mmol g-1 h-1), respectively. Moreover, the composite also exhibits excellent stability with a well-reproducible HER performance over a 66-hour cyclic HER test of 15 cycles.