Low Hydrogen Research Articles

Subsidizing Grid-Based Electrolytic Hydrogen Will Increase Greenhouse Gas Emissions in Coal Dominated Power Systems.

Clean hydrogen has the potential to serve as an energy carrier and feedstock in decarbonizing energy systems, especially in "hard-to-abate" sectors. Although many countries have implemented policies to promote electrolytic hydrogen development, the impact of these measures on costs of production and greenhouse gas emissions remains unclear. Our study conducts an integrated analysis of provincial levelized costs and life cycle greenhouse gas emissions for all hydrogen production types in China. We find that subsidies are critical to accelerate low carbon electrolytic hydrogen development. Subsidies on renewable-based hydrogen provide cost-effective carbon dioxide equivalent (CO2e) emission reductions. However, subsidies on grid-based hydrogen increase CO2e emissions even compared with coal-based hydrogen because grid electricity in China still relies heavily on coal power and likely will beyond 2030. In fact, CO2e emissions from grid-based hydrogen may increase further if China continues to approve new coal power plants. The levelized costs of renewable energy-based electrolytic hydrogen vary among provinces. Transporting renewable-based hydrogen through pipelines from low- to high-cost production regions reduces the national average levelized cost of renewables-based hydrogen but may increase the risk of hydrogen leakage and the resulting indirect warming effects. Our findings emphasize that policy and economic support for nonfossil electrolytic hydrogen is critical to avoid an increase in CO2e emissions as hydrogen use rises during a clean energy transition.

Highly efficient and direct recovery of low-pressure hydrogen isotopes from tritium extraction gas by PdY alloy membrane permeator

Low-pressure hydrogen recovery is crucial for the fusion reactor deuterium-tritium fuel cycle, and the usual treatment is achieved through multiple steps of enrichment and separation, which has the drawbacks of complex processes and high energy consumption. In this work, a membrane permeator including 12 sets of Pd92Y8 at% alloy tubes has been investigated for the permeability and extraction of hydrogen in low-pressure mixtures. The hydrogen permeation through dense Pd-based membrane mechanism and corresponding Sieverts’ exponents have been verified. The concentration polarization effect is deducted from the results. Through pure hydrogen permeation test, the cold-rolling 80 μm thick Pd92Y8 at% membrane has hydrogen permeability at 400 °C of 3.43×10−8 mol∙m−1∙s−1∙Pa−0.5, which is higher than that of PdAg alloy membrane under the same conditions. Highly efficient recovery efficiency has been achieved for low hydrogen pressure mixtures, and the PdY alloy membrane permeator with 678 cm2 effective area could reach around 95% hydrogen extraction recovery for 0.1 mol% hydrogen-helium mixture and 97.74% recovery for 0.33 mol% at the rate of 21 standard liter per minute (SLM). It indicates that the PdY alloy membrane permeation can be an alternative solution for efficiently recovering low-pressure hydrogen isotopes in tritium extraction gas.

Effects of riboflavin application on rice growth under salinized soil conditions

Salt-sensitive crop varieties suffer from oxidative stress as a consequence of osmotic and ionic stresses in plants under salinity stress. This study is aimed at identifying the effects of riboflavin (RIB) application on uplifting rice growth under salinized soil condition. Two-week-old seedlings of IR29 (a salt-sensitive variety) were supplemented with 0.5 μM of RIB, and 50 mM of NaCl was supplied for 2 weeks, inducing salinized soil conditions. The results indicated that RIB pretreatment (RP) seedlings possessed higher plant biomass, and lower electrolyte leakage ration (ELR), hydrogen peroxide (H2O2) and malondialdehyde (MDA) concentrations, higher chlorophyll, magnesium (Mg), and iron (Fe) concentrations in the leaf blades, a higher proline concentration, and a lower Na+ concentration in the leaf blades. To further understand the mechanisms behind the difference in plant growth between the RP and non-RP seedlings, molecular analysis revealed that RP seedlings upregulated OsNHX1 and OsHKT1;5 expressions were observed in the roots of RP seedlings, regulating Na+ uptake through the transpiration stream and reducing Na+ concentration in the leaf blades. Collectively, these results suggest that RP is a potent method for improving plant growth under salinized soil conditions.

Waste-derived catalysts for tar cracking in hot syngas cleaning

Catalytic tar cracking is a promising technique for hot syngas cleaning unit in gasification plants because it can preserve tars chemical energy, so increasing the syngas heating value. The cost associated with catalyst preparation is a key issue, together with its deactivation induced by coke deposition. Iron is a cheap and frequently used catalyst, which can also be found in some industrial wastes. The study aims to assess the catalytic efficiency for tar cracking of two waste-derived materials (red mud and sewage sludge) having high content of iron. The catalysts were supported on spheres of γ-Al2O3, and their efficiency was compared to that of a pure iron catalyst. The role of support was investigated by testing pure red mud, with and without the support. A series of long-term tests using naphthalene as tar model compound were carried out under different values of process temperatures (750 °C-800 °C) and steam concentrations (0 %-7.5 %). The waste derived catalysts showed lower hydrogen yields compared to pure iron catalyst, due to their lower content of iron. On the other hand, the conversion efficiencies of all the tested catalysts resulted rather similar, since the Alkali and Alkaline-Earth Metallic species present on the surface of waste-derived catalyst help in preventing coke deposition. The iron oxidation state appears to play an important role, with reduced iron more active than its oxidised form in the tar cracking reactions. This indicates the importance of tuning steam concentration to keep constant the reduced state of iron while limiting coke deposition.

Hydrogen diffusion and hydrogen embrittlement of a 1500 MPa hot-stamped steel 22MnB5 in different austenitizing conditions

We investigated the influence of hydrogen on a 1500 MPa hot-stamped steel 22MnB5 with different prior austenite grain size (PAGS, ranging from 14.0 μm to 22.2 μm), which were produced by precise control of the austenitizing temperature and time. All steel specimen exhibited a significant reduction of ductility (e.g., by 70%) and a small decrease in ultimate tensile strength (≤15%), measured using the linearly increasing stress test. The effect of PAGS on hydrogen embrittlement of the hot-stamped steel was not significant for these test conditions. Martensite with smaller PAGS exhibited a slightly lower hydrogen diffusion coefficient. Fracture for all steel variants after yielding occurred for hydrogen contents greater than those that actually occur during service.

Policy Implementation Roadmap, Diverse Perspectives, Challenges, Solutions Towards Low-Carbon Hydrogen Economy

Hydrogen is a nearly emission-free energy carrier with many enticing qualities, including wide availability, environmental friendliness, and a high calorific value. There have constantly been a lot of challenges to establish an entire fledge low carbon hydrogen economy in the past century. This study aims to critically analyse the economic, environmental, technological, and policy implementation and division of low-carbon hydrogen to find novel solutions, bridging the gaps and giving a perspective approach to the study. Differentiation of various low carbon hydrogen (LCH) components, including green and blue hydrogen, was also proposed based on the life cycle assessment emissions (LCAE). Current policy perspectives and Promised Pledged Perspectives are considered to project hydrogen demand in 2030. A thorough economic analysis of low-carbon hydrogen system technologies is also conducted from both hydrogen production and storage perspectives by comparing various production and storage systems. Current Policies towards LCH were critically viewed from policymakers, consumers, and R & D perspectives, through which several challenges, gaps, and keynote necessities were also stated.

In-situ growth 2D Fe2P nanosheets on the surface of 1D Cd0.9Zn0.1S nanorods for remarkably improved photocatalytic H2 evolution

Loading cocatalysts can effectively reduce the hydrogen production overpotential and provide additional catalytic sites. Fe2P, with abundant active sites, low hydrogen evolution overpotential, is regarded as a promising cocatalyst to replace the noble metals. Fe2P nanosheets were grown in situ on the surface of Cd0.9Zn0.1S nanorods to form unique 2D/1D structure, which was designed to enlarge the interface contact between them. The maximum hydrogen evolution rate was as high as 38.48 mmol h−1 g−1, which was even higher than that of noble metal Pt modified Cd0.9Zn0.1S. The results of characterization and theoretical computation demonstrated that the electronic interaction existed between Fe2P and Cd0.9Zn0.1S, and Fe2P as cocatalyst collected electrons to facilitate the transfer and separation of electrons and holes. This work investigated the transfer process of photogenerated carriers and revealed the photocatalytic mechanism through a combination of theoretical calculation and experimental characterization.

Removal of molybdenum by TBP-TRPO extraction in sodium isopolytungstate solution

A new process was proposed for extracting molybdenum from tungsten solutions in acidic tungsten-molybdenum mixed solution. The extraction ratio of molybdenum reached 70 % and the tungsten-molybdenum separation factors reached 400 with the hydrogen peroxide dosage of nH2O2/n(Mo) = 2 (nH2O2/n(W + Mo) = 0.3) for the molybdenum-containing isopolytungstate sodium solution. The experimental conditions resulted in the yield of only 20 % of the traditional method (nH2O2/n(W + Mo) = 1.5–2). The organic phases consisted of 2 % TRPO and 60 % TBP. The saturated extraction capacity of molybdenum was found to be 10 g/L. The solution of 0.3 mol/L sodium bicarbonate was used as the stripping agent. With the temperature of 25 ℃, stripping time of 6 min, and the phase ratio of (O/A)2, the stripping ratio of molybdenum was 90 % and that of tungsten was 70 %. The extraction mechanism of TBP-TRPO and the hydrogen peroxide coordination were analyzed using Raman and infrared analyses. The process has a high industrial potential due to its low hydrogen peroxide dosage, high molybdenum extraction ratio, high separation factor, and low cost.

The effect of direct energy deposition arc mode on the porosity of AA5087 aluminum alloy

The paper evaluates the effect of the welding mode of the CMT-based direct energy deposition arc (DED-Arc) process on the porosity of AA5087 aluminum alloy walls. Three welding modes were used to produce the walls: cold metal transfer (CMT), CMT-Pulse (CMT-P), and CMT Cycle-Step (CMT-CS) with heat inputs of 128.5 J/mm, 150.4 J/mm, and 152 J/mm, respectively. Porosity was assessed with a light microscopy (LM) and computer tomography (CT). The wall produced with the lowest heat input had the lowest average porosity of 0.641 % compared to CMT-P (0.799 %) and CMT-CS (0.766 %). CT results followed the same trend with porosity of 0.21 %, 0.32 %, and 0.27 % for CMT, CMT-P, and CMT-CS, respectively. The porosity level strongly correlates with the hydrogen content. The lowest porosity (CMT) at the lowest hydrogen content (5.29 ppm) is associated with lower hydrogen solubility in a molten pool at lower heat inputs. Most of the detected pores in all modes ranged from 51 to 100 μm in size.

Synergistic development of nonvascular species microalgae for bio-hydrogen production featured with nano titanium dioxide additive

With technological growth, renewable biofuel energy sources, extracted from organic materials and microalgae feedstock's rich energy substance, have the potential for future energy applications. Moreover, syngas production is limited due to microalgae processing. The prime aim of this research is to enhance the bio-hydrogen extraction by the source of sewage sludge and harvesting of microalgae from non-vascular species (Bryothyta) water with the integration of 0.05, 0.1, 0.15, and 2vol% of titanium dioxide (TiO2) nano additive. Influences of TiO2 concentration on synergistic specific microalgae growth are monitored concerning day and observed that the higher content (2vol%) of TiO2 own 0.87 microns/day, which involves hydrothermal gasification process configured with potassium hydroxide catalyst operating with 400, 500, 600, and 700 ⁰C gasification temperature under 60min time gap. Gasification temperature influencing molar fraction, bio-methane & and hydrogen yield, low heating value, hydrogen selectivity, and gasification efficiency is experimentally studied. With the importance KOH adopted hydrothermal gasifier functioned with higher gasification temperature of 700⁰C operated by 60min offered higher molar fractions of 62% in hydrogen & 17% in bio-methane, superior bio-methane & hydrogen yield of 9.1& 23mol/kg, reduced low heating value of 9.3 MJ/Nm3, higher hydrogen selectivity of 18.5, and superior gasification efficiency of 66%.

Superior specific capacity and energy density simultaneously achieved by Sr/In co-deposition behavior of Mg-Sr-In ternary alloys as anodes for Mg-Air cells

In this work, the combined addition of strontium/indium (Sr/In) to the magnesium anode for Mg-Air Cells is investigated to improve discharge performance by modifying the anode/electrolyte interface. Indium exists as solid solution atoms in the α-Mg matrix without its second-phase generation, and at the same time facilitates grain refinement, dendritic segregation and Mg17Sr2-phases precipitation. During discharge operation, Sr modifies the film composition via its compounds and promoted the redeposition of In at the substrate/film interface; their co-deposition behavior on the anodic reaction surface enhances anode reaction kinetics, suppresses the negative difference effect (NDE) and mitigates the “chunk effect” (CE), which is contributed to uniform dissolution and low self-corrosion hydrogen evolution rate (HER). Therefore, Mg-Sr-xIn alloy anodes show excellent discharge performance, e.g., 0.5Sr-1.0In shows an average discharge voltage of 1.4234 V and a specific energy density of 1990.71 Wh kg−1 at 10 mA cm−2. Furthermore, the decisive factor (CE and self-discharge HE) for anodic efficiency are quantitively analyzed, the self-discharge is the main factor of cell efficiency loss. Surprisingly, all Mg-Sr-xIn anodes show anodic efficiency greater than 60% at high current density (≥10 mA cm−2), making them excellent candidate anodes for Mg-Air cells at high-power output.

Hydrogen enhanced localised plasticity of single grain α titanium verified by in-situ hydrogen microcantilever bending

The effect of hydrogen on the micromechanical characteristics of pure grade 2 titanium was investigated by comparing prenotched microcantilever bending in air versus in-situ electrochemical hydrogen charging. The nanoscale interaction between hydrogen and the metal's defects was analysed in three different grain orientations, i.e. the top surface parallel to {101‾2}, {0001}, and {202‾1}. The subsequent high resolution post-mortem characterisation enabled to characterise the interplay between hydrogen in solid solution and the dislocations in the local deformation process. The results showed that hydrogen facilitated a localised plasticity mechanism, causing hydrogen assisted degradation at the applied low hydrogen concentration below the hydride formation threshold. Meanwhile, hydrogen provoked a reduction in defect formation energy, following the defactant concept, which was responsible for a softening effect on the yield stress and flow stress. Furthermore, due to the anisotropic characteristics of the α titanium hexagonal close packed crystal lattice, the susceptibility to hydrogen effects also depended on the grain orientation. This single grain in-situ micromechanical testing is complementing the existing macroscaled identification of hydrogen effects in α titanium.

A novel solution to improve static and dynamic retention characteristics by enhancing hydrogen passivation with in situ LD-TEOS/TEOS dual layer

We proposed a novel solution to improve both static and dynamic retention characteristics by additional etching of the thickness of Silicon Boron Nitride (SIBN), stopper when oxide etch, with in situ dual low deposition-tetraethyl orthosilicate (LD-TEOS)/TEOS Dual layer. As Dynamic Random Access Memory Cells shrink, it is difficult to obtain reliable retention properties, so it becomes more significant to reduce the number of interface trap (Nit) by hydrogen passivation. In this work, Nit decreased by reducing the thickness of SIBN, which has low hydrogen diffusion coefficients, improve the static and dynamic retention characteristics simultaneously through enhancing hydrogen passivation with in situ LD-TEOS Dual layer compensating for Metal contact to Other Bit line pad distance margin risk.

Boosting visible-light-driven hydrogen evolution through Pt site anchored 2D/2D heterostructure catalyst: Cd-TCPP(Pt)@CdS

Solar-powered water splitting is an up-and-coming method for hydrogen production. Still, it faces several challenges, including improving light responsiveness, maximizing utilization of photocatalyst active sites, and effectively utilizing photo-induced carriers to prevent low hydrogen production. In this research, we propose an approach for designing a 2D/2D heterostructure catalyst, the Cd-TCPP(Pt)@CdS, which consists of 2D CdS nanosheets (NSs) and a 2D metal-organic framework (MOF) with Pt active sites (Cd-TCPP(Pt)), aiming to achieve highly efficient visible-light-driven hydrogen evolution. Firstly, CdS NSs exhibit excellent responsiveness to visible light, ensuring robust generation of photo-induced carriers. Secondly, the 2D MOF provides abundant Pt active sites, enhancing electron utilization and reducing the energy barrier for proton reduction. Compared to pure CdS NSs (which demonstrate a hydrogen production activity of 1220 μmol/g/h), the newly designed 2D/2D composite catalyst Cd-TCPP(Pt)@CdS exhibits an activity of 13,434 μmol/g/h, representing an 11-fold increase. Impressively, Cd-TCPP(Pt)@CdS maintains a high activity of 3062 μmol/g/h even under sunlight. density functional theory (DFT) calculations were employed to investigate the principle of proton reduction. The suitable bandgap of CdS and energy gap of 2D Cd-TCPP(Pt) contribute to their strong interaction and consequently higher efficiency in hydrogen evolution. The Pt-single atom (Pt-SA) also provides sites with low free energy for proton reduction, contributing to improved activity. The photocatalytic performance of Cd-TCPP(Pt)@CdS NSs composites demonstrates a synergistic effect between the 2D inorganic semiconductor and the 2D MOF containing the Pt-site, resulting in enhanced utilization of photo-induced carriers and atoms.

Light curve and spectral modelling of the type IIb SN 2020acat

We use the light-curve and spectral synthesis code JEKYLL to calculate a set of macroscopically mixed type IIb supernova (SN) models, which are compared to both previously published and new late-phase observations of SN 2020acat. The models differ in the initial mass, in the radial mixing and expansion of the radioactive material, and in the properties of the hydrogen envelope. The best match to the photospheric and nebular spectra and light curves of SN 2020acat is found for a model with an initial mass of 17 M⊙, strong radial mixing and expansion of the radioactive material, and a 0.1 M⊙ hydrogen envelope with a low hydrogen mass fraction of 0.27. The most interesting result is that strong expansion of the clumps containing radioactive material seems to be required to fit the observations of SN 2020acat both in the diffusion phase and in the nebular phase. These Ni bubbles are expected to expand due to heating from radioactive decays, but the degree of expansion is poorly constrained. Without strong expansion, there is a tension between the diffusion phase and the subsequent evolution, and models that fit the nebular phase produce a diffusion peak that is too broad. The diffusion-phase light curve is sensitive to the expansion of the Ni bubbles because the resulting Swiss-cheese-like geometry decreases the effective opacity and therefore the diffusion time. This effect has not been taken into account in previous light-curve modelling of stripped-envelope SNe, which may lead to a systematic underestimate of their ejecta masses. In addition to strong expansion, strong mixing of the radioactive material also seems to be required to fit the diffusion peak. It should be emphasized, however, that JEKYLL is limited to a geometry that is spherically symmetric on average, and large-scale asymmetries may also play a role. The relatively high initial mass found for the progenitor of SN 2020acat places it at the upper end of the mass distribution of type IIb SN progenitors, and a single-star origin cannot be excluded.

Functionalized Linear Conjugated Polymer/TiO2 Heterojunctions for Significantly Enhancing Photocatalytic H2 Evolution.

Conjugated polymers (CPs) have attracted much attention in recent years due to their structural abundance and tunable energy bands. Compared with CP-based materials, the inorganic semiconductor TiO2 has the advantages of low cost, non-toxicity and high photocatalytic hydrogen production (PHP) performance. However, studies on polymeric-inorganic heterojunctions, composed of D-A type CPs and TiO2, for boosting the PHP efficiency are still rare. Herein, an elucidation that the photocatalytic hydrogen evolution activity can actually be improved by forming polymeric-inorganic heterojunctions TFl@TiO2, TS@TiO2 and TSO2@TiO2, facilely synthesized through efficient in situ direct C-H arylation polymerization, is given. The compatible energy levels between virgin TiO2 and polymeric semiconductors enable the resulting functionalized CP@TiO2 heterojunctions to exhibit a considerable photocatalytic hydrogen evolution rate (HER). Especially, the HER of TSO2@TiO2 heterojunction reaches up to 11,220 μmol g-1 h-1, approximately 5.47 and 1260 times higher than that of pristine TSO2 and TiO2 photocatalysts. The intrinsic merits of a donor-acceptor conjugated polymer and the interfacial interaction between CP and TiO2 account for the excellent PHP activity, facilitating the separation of photo-generated excitons. Considering the outstanding PHP behavior, our work discloses that the coupling of inorganic semiconductors and suitable D-A conjugated CPs would play significant roles in the photocatalysis community.

MgH2@Mg(BH4)2 Core-Shell-like Nanostructures: Synthesis, Hydrolysis Performance, and Promotion Mechanism.

The hydrolysis of hydrides, represented by MgH2, delivers substantial capacity and presents an appealing prospect for an on-site hydrogen supply. However, the sluggish hydrolysis kinetics and low hydrogen yield of MgH2 caused by the formation of a passivation Mg(OH)2 layer hinder its practical application. Herein, we present a dual strategy encompassing microstructural design and compounding, leading to the successful synthesis of a core-shell-like nanostructured MgH2@Mg(BH4)2 composite, which demonstrates excellent hydrolysis performance. Specifically, the optimal composite with a low Ea of 9.05 kJ mol-1 releases 2027.7 mL g-1 H2 in 60 min, and its hydrolysis rate escalates to 1356.7 mL g-1 min-1 H2 during the first minute at room temperature. The nanocoating Mg(BH4)2 plays a key role in enhancing the hydrolysis kinetics through the release of heat and the formation of local concentration of Mg2+ field after its hydrolysis. This work offers an innovative concept for the design of hydrolysis materials.

Research Progress of Hydrogen Storage Materials

Hydrogen energy has become increasingly popular as a clean and renewable source of energy in recent years due to the high levels of carbon pollution worldwide. This essay examines the current research status on various hydrogen storage techniques and materials for hydrogen energy. There are currently three primary hydrogen storage methods: high-pressure gaseous hydrogen storage, low-temperature liquid hydrogen storage, and solid-state hydrogen storage. The most widely employed method in China is high-pressure gaseous hydrogen storage. It entails compressing hydrogen fuel into a container under high pressure. As a result, high-pressure gaseous hydrogen storage is commonly used for stationary hydrogen storage. Low temperature liquid hydrogen storage involves compressing the hydrogen at first and then cooling it down with liquefaction technology. However, due to the strict requirements for compression and container insulation, its actual performance is often limited. This paper focuses on the study of solid hydrogen storage materials. The physical adsorption materials that are successively introduced include carbon-based hydrogen storage materials, metal-organic frameworks (MOFs), and Covalent organic frameworks (COFs). In the current study, carbon-based hydrogen storage materials show better performance only in low-temperature and high-pressure environments, but MOFs and COFs have great prospects in hydrogen storage. The chemical absorption hydrogen storage materials introduced in this paper are metal alloy hydrogen storage and hydrogenation complexes hydrogen storage, mainly rare earth-based hydrogen storage materials and magnesium-based hydrogen storage materials. Among them, magnesium-based hydrogen storage materials have become one of the most promising hydrogen storage materials due to their low cost and good hydrogen storage performance.

Toward High-Energy-Density Fuels for Direct Liquid Organic Hydrogen Carrier Fuel Cells: Electrooxidation of 1-Cyclohexylethanol.

Electrochemically active liquid organic hydrogen carriers (EC-LOHCs) can be used directly in fuel cells; so far, however, they have rather low hydrogen storage capacities. In this work, we study the electrooxidation of a potential EC-LOHC with increased energy density, 1-cyclohexylethanol, which consists of two storage functionalities (a secondary alcohol and a cyclohexyl group). We investigated the product spectrum on low-index Pt single-crystal surfaces in an acidic environment by combining cyclic voltammetry, chronoamperometry, and in situ infrared spectroscopy, supported by density functional theory. We show that the electrooxidation of 1-cyclohexylethanol is a highly structure-sensitive reaction with activities Pt(111) ≫ Pt(100) > Pt(110). Most importantly, we demonstrate that 1-cyclohexylethanol can be directly converted to acetophenone, which desorbs from the electrode surface. However, decomposition products are formed, which lead to poisoning. If the latter side reactions could be suppressed, the electrooxidation of 1-cyclohexylethanol would enable the development of EC-LOHCs with greatly increased hydrogen storage capacities.

Low and high hydrogen peroxide concentrations of in-office dental bleaching associated with violet light: an in vitro study.

This study aims to assess hydrogen peroxide (HP) penetration within the pulp chamber, color change (CC), physical-chemical properties, and temperature using in-office different concentration bleaching gels with or without violet light. Fifty teeth were divided into five groups (n = 10) based on the HP concentration bleaching gels used (6% and 35%) and the used violet light (with or without). HP penetration within the pulp chamber was measured using UV-Vis. The CC was evaluated with a digital spectrophotometer. Initial and final concentration, and pH were measured through titration, and a Digital pHmeter, respectively. Temperature analyses were measured through a thermocouple. Statistical analysis included two-way ANOVA, Tukey's, and Dunnett's test(α = 0.05). The presence of violet light did not affect the amount of HP within the pulp chamber, or the CC (p > 0.05). Greater penetration of HP was observed within the pulp chamber, as well as CC when using 35% HP (p < 0.05). The final concentration of both gels was lower than the initial concentration, regardless of the use of violet light (p < 0.05). The initial and final pH levels remained neutral and stable (p > 0.05). The pulp temperature increased when the gels were used in conjunction with violet light (p < 0.05). Using violet light in conjunction with 6% or 35% HP does not alter the physical properties of the bleaching agents, the penetration of HP or enhance color change. However, an increase in temperature was observed when violet light was applied associated with bleaching gels. While the simultaneous use of violet light with hydrogen peroxide 6% or 35% does not alter the material's properties, it also does not bring benefits in reducing hydrogen peroxide penetration and improving color change. Furthermore, the use of violet light increases pulp temperature.