Cr 2O3 Research Articles

High-temperature oxidation behavior of GH4169 and Inconel617 nickel-based superalloys in SOFC environment

Field exposure for 5000h combined with weight gain measurement and morphology/composition analysis of oxide film were conducted to examine high temperature oxidation behavior of GH4169 and In617 nickel-based super alloys in SOFC system environment. The In617 alloy has been found to demonstrate excellent oxidation resistance in the SOFC environment because of its high Ni content. An integral and dense NiO oxide film can be developed in the outer layer with a continuous Cr2O3 oxide film formed in inner layer. It indicates that NiO played a crucial role in the formation of an integral and dense oxide film. In contrast, GH4169 alloy failed to develop a continuous and dense oxide film probably due to high Fe content, in which case Fe-dopped chromium oxide (Fe,Cr)2O3 was formed. As a result, the oxide film was loose and porous, leading to relatively poor oxidation resistance.

In-situ reaction-generation self-healing superior antioxidation layer induced by Al-Y sol-gel film on the AISI304 steel

In this study, an Al-Y sol-gel film is prepared on the AISI304 steel and its effect on the high temperature oxidation resistance is evaluated by the cycle oxidation at 900 ℃ in the air. The resulting intact oxide layer, composed of (Al, Cr)2O3 and MnCr2O4 phases, effectively slowing down the oxidation rates at 900 ℃. The general cracks in the sol-gel film during the oxidation process are found to be self-healed by a growing spinel MnCr2O4 phase from the substrate, attributed to its low Gibbs free energy and the sufficient Cr source from the adjacent substrate. Furthermore, the oxide layer originates from the interaction between sol-gel film and the substrate which enhances the binding between the oxide layer and the substrate. Thus, it could be confirmed that a self-healing superior antioxidation layer is generated on the surface of AISI304 steel through an in-situ reaction induced by the Al-Y sol-gel film during high-temperature oxidation procedure.

High Temperature Oxidation Behavior of ODS Ferritic Stainless Steel Fe-16Cr-4Al-1Ni-0.4Y<sub>2</sub>O<sub>3</sub>

This study investigates the isothermic oxidation behavior of the new ODS alloy Fe-16Cr-4Al-1Ni-0.4Y2O3 (% by weight) at 700, 800 and 900 °C, with exposure times of 5, 20, 50, and 100 h at each temperature. The purpose is to obtain new data on its high-temperature parabolic oxidation constant for assessing oxidation resistance. The methods used include isothermal oxidation testing, XRD, SEM-EDS characterization, and analysis of oxidation kinetics by monitoring changes in oxide thickness using microscopy and SEM-EDS. The oxide products formed on the sample surface are Fe2O3, Fe3O4, AlFe2O4, and (Fe,Cr)2O3. Al and Cr oxides are located under the dominant Fe oxide layer on the surface of the sample. The oxidation test results showed that the most protective sample was obtained at a temperature of 700 °C for 100 h with an oxide thickness of 263.99 μm. The kinetics analysis correlates strongly with the parabolic equation (R2 ≈ 1). The oxidation rate constants at temperatures of 700, 800, and 900 °C were 681.76, 2957.5, and 12300 μm2 h−1, respectively. The activation energy required by the oxidation reaction in this alloy is 136.5 kJ mol−1. This research enhances understanding and potential applications of the Fe-16Cr-4Al-1Ni-0.4Y2O3 alloy in high-temperature environments.

Preparation and properties of ZTA/alloyed high manganese steel composites

In the long-term use of high manganese steels, it is not desirable to achieve wear resistance by austenite deformation strengthening alone. The wear resistance of high manganese steel is much lower than that of ordinary wear-resistant steel under medium and low stress conditions. Improving the instability of wear resistance caused by defects in high manganese steels is an important problem to be solved in current industrial production. In this study, a new type of high manganese alloy with high hardness and high wear resistance was prepared by multi-alloying with Cr-W-Mo elements on the basis of 20Mn1.2C. ZTA ceramic particles reinforced high manganese steel composites were prepared by selecting high manganese steel materials with excellent mechanical properties as the metal matrix of ceramic reinforced metal matrix composites. The Cr-W-Mo multi-alloyed high manganese alloys are mainly composed of a mixed austenite and ferrite matrix, M3C-type cementite and M6C-type carbides. The Cr2W6Mo6 sample has the best overall mechanical properties. Its hardness reached 49.8 HRC, which is 1.20 times higher than that of the Cr2 sample. The mass loss was 0.2571 g, which is 79.92% of the Cr16 sample (0.3217 g). The ZTA ceramic particles were well composited with the alloyed high manganese steel matrix, and the thickness of the interfacial layer was 20-30 μm, with the formation of Mn2AlO4 and (Fe, Mn)2SiO4, and (Al, Cr)2O3 in the interfacial layer. The best abrasion resistance was obtained at a ZTA content of 40 vol.%. The mass loss was 0.1669 g, which is 51.88% of the Cr16 material (0.3217 g).

Effect of surface orientation on the corrosion behavior of Ni-based single-crystal alloy in a simulated marine atmosphere at 750 °C

DD5 single-crystal alloy samples with different surface orientations were obtained by machining the alloy ingot perpendicular (PP) and parallel (P), respectively, to its solidification direction (SD). The corrosion behaviors of the PPSD and PSD alloy samples were investigated in the atmosphere of moist air + NaCl aerosol at 750 °C. Results showed that during initial corrosion, γ′ phase developed a thin NiO layer with Al internal corrosion product. However, a NiO nodule with an internal Cr2O3 layer was formed on γ phase. As corrosion progressed, the corrosion product gradually grew to a NiO/(Al, Cr)2O3 bilayer, accompanied by internal corrosion consisting of Al2O3. It was also found that the PSD sample with a lower fraction and smaller size of γ’ phases exhibited better corrosion resistance than the PPSD sample. The effect of alloy surface orientation on the corrosion mechanism was discussed.

Comparison of diffusion coatings resistance on ferritic and austenitic-stainless steels at 650 °C in steam oxidation

Iron-aluminide coatings were deposited on T24, P92 and Incoloy 800HT (IN-800HT) by pack-cementation and by a water-based slurry. According to the differences in heat treatments between the two processes, Al-rich phases, i.e. Fe4Al13 and Fe2Al5 were obtained by pack cementation and only B2-(Fe, Ni)Al by slurry. Vertical or horizontal cracks were present on certain coatings, the former being due to the coefficient of thermal expansion (CTE) mismatch with the substrate while the latter were related to the brittleness of the Al-rich phases. The oxidation behaviour of uncoated and coated substrates was studied at 650 °C up to 1000 h under a low steam flow rate (1.07 × 10−5 m/s). The aluminide coatings were very protective on the low Cr substrates (i.e. T24 and P92) because of the formation of a very thin oxide scale compared to the non-protective thick layers of Fe3O4 and Fe2O3 that grew on both uncoated substrates. In contrast, none of the coatings significantly improved the oxidation resistance of the IN-800HT steel despite the growth of a thin oxide layer made of (Fe, Cr)2O3 and (Fe, Cr)3O4 at 650 °C.

Oxygen concentration – A governing parameter for microstructural tailoring of duplex AlCrSiON coatings for superior mechanical, tribological, and anti-corrosion performance

This study investigates the impact of increasing oxygen levels on structure, and mechanical properties and tribological performance of duplex AlCrSiON coatings. AISI H13 steel and tungsten carbide substrates are coated using arc ion plating with increasing oxygen flow rate up to 200 sccm with varying oxygen concentration. High-resolution transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and three-dimensional profilometer are used to study morphological and structural evolution. Correspondingly, the coatings are assessed for hardness, adhesion strength, friction coefficient, and resistance against corrosion and wear. A 50–100 sccm oxygen flow rate is considered as an optimal range to receive lower surface roughness. Generally, the addition of oxygen has compromised hardness and friction coefficient but improve adhesion strength, wear and corrosion resistance with increasing oxygen concentration. The immersion tests have identified pitting corrosion as a dominating failure mechanism for AlCrSiON coatings when exposed to molten A380 aluminium alloy. This corrosion resistance stems from their dense microstructure, excellent thermal stability, and the presence of fcc-(Al, Cr)2O3 phase structure. This study demonstrates that controlled oxygen concentration is a crucial parameter for tuning the microstructure of AlCrSiON coatings to achieve superior mechanical, tribological, and anti-corrosion performance, particularly for high-pressure die-casting applications.

Superior anti-oxidation layer induced by PVA-boehmite sol-gel film on AISI304 steel

The superior anti-oxidation layer induced by the PVA-boehmite sol-gel film on the AISI304 steel during the cyclic oxidation is investigated in this work. The moderate PVA addition in the boehmite sol conduces to increase the film thickness and is beneficial to the adhesion between the film and the substrate. The presence of the PVA-boehmite film leads to a significant reduction in mass gain during the high-temperature cyclic oxidation at 800 °C, demonstrating the enhanced oxidation resistance. The generated oxide layer induced by the PVA-boehmite film presents as a thin, compact, and continuous layer without spalling, offering sustainable protection against oxidation etching. The PVA-boehmite film promotes the preferential formation of the corundum (Al, Cr)2O3 phase rather than the detrimental hematite Fe2O3 phase during the oxidation procedure, which facilitates the development of the above compact oxide layer. Finally, the superior anti-oxidation oxide layer is characterized as a novel dual-layer structure: the outer spinel MnCr2O4 layer and the inner corundum (Al, Cr)2O3 layer, effectively delaying the oxidation process.

Microstructure evolution, mechanical characteristics and erosion behavior of Cr2O3–Al2O3–MgO–ZrO2 refractories in molten reduction slag

In order to overcome the serious corrosion problem of furnace hearth refractory materials for smelting reduction ironmaking, the Cr2O3–Al2O3–MgO–ZrO2 refractories were synthesized, and the phase component, microstructure, mechanical characteristics, and slag erosion behavior of composite refractories were investigated and evaluated. The results indicate that the composite refractories mainly consist of Mg(Al, Cr)2O4 spinel phase, (Al, Cr)2O3 solid solution and ZrO2. The content of Mg (Al, Cr)2O4 spinel significantly increases with the increasing MgO content, while the content of (Al, Cr)2O3 obviously decreases. Furthermore, the comprehensive mechanical properties of the MgO modified composite refractories can be obviously enhanced by increasing the MgO content, and sample S4 presents the best mechanical characteristics when the MgO addition is 10 wt%. The corresponding hardness, compressive strength and bending strength are 14.22 GPa, 267.14 MPa and 80.0 MPa, respectively. This is mainly because the formation of Mg(Al, Cr)2O4 significantly improves the densification of composite refractories, and a large number of high-strength Mg (Al, Cr)2O4 spinel “bridge” formed between the large-sized (Al, Cr)2O3 grains. The erosion test results indicate that increasing the MgO content can significantly improve the slag infiltration resistance of composite refractories, because the formation of Mg (Al, Cr)2O4 spinel layer significantly improves the densification of MgO reinforced composite refractories. Although the slag corrosion resistance of Mg(Al, Cr)2O4 is lower than that of (Al, Cr)2O3, the Cr2O3–Al2O3–MgO–ZrO2 refractories still presents good erosion resistance, permeability resistance, and excellent mechanical characteristics.

Physiological and Morphological Response of Heavy Metal Stress in Vigna mungo (L.) Hepper

Introduction: Heavy metals such as manganese (Mn), magnesium (Mg), chromium (Cr), and nickel (Ni) negatively impact plant growth and productivity. Understanding plant responses to heavy metal stress is crucial for developing strategies to mitigate these effects in agriculture. Aim/Objectives: This study aims to investigate the impact of various heavy metals (Mn, Mg, Cr, and Ni) on the physiological and morphological responses of Vigna Mungo (L.) Hepper. Key objectives include evaluating the effects of different concentrations of these heavy metals on plant growth, productivity and photosynthetic efficiency. Method/Materials: A field experiment was conducted using a series of pots filled with soil, treated with different concentrations of MnCl2 , MgSO4 , Cr2 O3 , and Ni. Control samples without heavy metals were also maintained. Key parameters, including plant height, number of branches, number of pods, pod length, fresh and dry weight of pods, number of seeds per pod, weight of 100 seeds, root nodules, and chlorophyll content, were recorded and statistically analysed. Results: Heavy metal stress significantly inhibited plant growth and productivity, with decrease in plant height, number of branches, pods per plant, pod length, fresh and dry pod weight, and seeds per pod. High chromium concentrations prevented pod formation. Root nodules decreased, affecting nitrogen fixation. Chlorophyll content decreased in Mn, Ni, and Mg-treated plants but unexpectedly increased at higher Cr concentrations, indicating complex interactions with chlorophyll synthesis. Discussion: The findings show that heavy metal stress significantly inhibits plant growth and productivity, consistent with previous studies. Symptoms such as stunting, and chlorosis indicate disruptions in metabolic processes. This study underscores the need to monitor and manage heavy metal levels in agricultural soils to protect crop health and productivity. Developing soil remediation strategies and heavy metal-tolerant plant varieties is crucial for sustainable agriculture. Further research is needed to understand plant responses to heavy metal stress and enhance plant tolerance.

Enhancing oxidation resistance of ferritic heat-resistant stainless steel in air atmosphere at 1100 °C by self-repairing oxide layer

The oxidation behaviors of Al-free and 1Al ferritic heat-resistant stainless steels (FHSSs) at 1100 °C were investigated. After oxidation for 100 h, the Al-free FHSS had triple oxide layers of a first layer Fe2O3 + MnCr2O4, a second layer MnCr2O4 + Cr2O3 + MnO, a third layer SiO2 and oxides of Nb and Ti. The 1Al FHSS had double oxide layers of a first layer Ti-bearing (Al, Cr)2O3 particles, a second layer dense (Al, Cr)2O3. The (Al, Cr)2O3 layer with self-repairing feature can reduce the thickness of oxide layer by 515 times, and reduce the oxidation weight gain rate of the FHSS by 5 orders of magnitude.

ZTA/high Ni–Cr alloy steel composites prepared by liquid phase sintering

The interfacial bonding, wear resistance, corrosion resistance and high temperature oxidation resistance of ZTA/high Ni–Cr alloy steel composites prepared by liquid phase sintering were investigated. The results showed that the ZTA particles bonded well with high Ni–Cr alloy steel matrix and produced transition new phases, including (Al, Cr)2O3, Al60Mn11Ni4, Mn2SiO4, MnCr2O4, (Mn, Fe)2SiO4 and MnSiO3. With the addition of ZTA particles, the wear resistance of the composites was reduced substantially. When the ZTA content is 40 vol%, the wear resistance is two times of the matrix, which is better than that of the Cr16 material. The small content of ZTA particles added can enhance the corrosion resistance of the composites. When ZTA was in small amounts, there was passivation of the samples and the corrosion resistance increased. When the content of ZTA reaches 30 vol%, the passivation phenomenon disappears. The corrosion resistance of the composites is much higher than that of the Cr16 material. The composites have good resistance to high temperature oxidation at temperatures below 700 °C. Industrial testing of plate hammers was carried out on a corrosive slag machine at a high temperature of 700 °C. The results show that the ZTA/high Ni–Cr alloy steel composite has twice the service life of the Cr26 material.

Growth of 2D Cr2 O3 -CrN Mosaic Heterostructures with Tunable Room-Temperature Ferromagnetism.

2D magnets have generated much attention due to their potential for spintronic devices. Heterostructures of 2D magnets are interesting platforms for exploring physical phenomena and applications. However, the controlled growth of 2D room-temperature ferromagnetic heterostructures is challenging. Here, one-pot chemical vapor deposition growth of stable 2D Cr2 O3 -CrN mosaic heterostructures (MHs) is reported with a controlled ratio of components that possess robust room-temperature ferromagnetism. The 2D MHs consist of Cr2 O3 flakes with embedded CrN subdomains and the CrN:Cr2 O3 ratio can be tuned from 0% to 100% during growth. By changing the CrN:Cr2 O3 ratio, the ferromagnetism of the MHs (e.g., saturation magnetization, coercive field), which originates from the interfacial coupling between Cr2 O3 and CrN, can be controlled. Importantly, the obtained Cr2 O3 -CrN MHs are stable in air at elevated temperatures and have robust ferromagnetism with Curie temperature >400K. This work presents a facile method for fabricating 2D MHs with tunable magnetism which will benefit high-temperature spintronics.

Stabilizing Cr3+ in a mixture of solid solution phases for high-temperature applications

The major drawback of Cr-containing materials is the generation of toxic Cr6+ compounds, especially at high temperatures in contact with oxygen, alkali or alkaline earth elements/oxides/salts. In this work, we compared the oxidation of two different Cr3+ species, (a) Cr2O3 and (b) a solid-solution mixture of Ca(Al,Cr)12O19 and (Al,Cr)2O3, upon reheating (500–1500 °C) in the presence of CaO, Al2O3, and SiO2 under air atmosphere. The mixture of Ca(Al,Cr)12O19 and (Al,Cr)2O3 was found to be more stable (7.5 mg/kg Cr6+) than Cr2O3 (5646 mg/kg Cr6+). Prolonged reheating (up to 24 h) of Cr3+ solid-solution phases at 900 °C reveals a slight increase in Cr6+ (3.0 to 4.8 mg/kg and 7.5 to 9.1 mg/kg for sample M2 and M2-S (with SiO2), respectively). However, the Cr3+ solid-solution phases in the presence of SiO2 reveal higher Cr-evaporation than undoped counterparts. Nonetheless, the mixture of (Al,Cr)2O3 and Ca(Al,Cr)12O19 hardly showed reoxidation and was more inert.

Effect of Cr2O3 Addition on Sintering Behavior of Novel Chromite‐Based Ladle Filler Sand

Developing novel filler sands has garnered significant interest in improving the ladle's free‐opening rate and enhancing the cleanliness of high‐Mn and high‐Al steel. Laboratory studies explore the effect of adding Cr2O3 powder on the sintering behavior of chromite‐based filler sands. Furthermore, interfacial phenomena are examined between the sands and the steel grades, varying in Mn contents. The results demonstrate that adding Cr2O3 power plays a role in inhibiting the liquid phase formation in the sand. With a 16% addition, the steel (Mn mass% = 30) reacts with the sand, leading to the shape of a spinel phase, specifically (Mn, Fe, Mg)O·(Al, Cr)2O3, which facilitates the separation of the liquid phase. The reduction of FeO to Fe by Mn, Al, and C in steel, especially Al, is hindered by adding Cr2O3, resulting in a suitable sintering degree that ultimately benefits ladle free‐opening. SiO2 is crucial for forming the liquid phase during the sintering process. The SiO2 content of the sand should be about 20% to achieve optimal sintering effects. Chromite sand for casting is not suitable for the steels. The mixed sand presented in the current study demonstrates potential as a suitable filler sand for the steel (20 ≤ Mn mass% ≤ 30).

Towards Industry 4.0 and Sustainable Manufacturing Applying Environmentally Friendly Machining of a Precipitation Hardened Stainless Steel Using Hot Turning Process

This study aims to address the aforementioned challenges, solutions and implementation perspectives with regard to sustainable manufacturing. In this research, the conventional and hot turning of AISI630 hardened stainless steel have been investigated using PVD-(Ti,Al)N/(Al,Cr)2O3 coated carbide cutting tools at various feed rates and cutting speeds. The high hardness of AISI630, along with the low thermal conductivity, has made it one of the most difficult-to-cut materials, and consequently, its machining is associated with high tool wear and poor workpiece surface quality. AISI630 stainless steel is used in the manufacture of pressure vessels and components exposed to high-stress and corrosive environments in the oil and gas industries. In the present research work, tool flank wear and crater wear mechanisms have been studied in different cutting conditions as well as different preheating temperatures using SEM microscopy. Experimental results showed that hot turning operation at temperatures up to 300 °C reduces flank wear by 33% and improves machined surface roughness by 23%. In addition, FEM simulation has been developed to predict tool tip temperature and cutting forces during turning processes. Experimental and FEM analysis shows that cutting force reduction at a preheating temperature of 300 °C is one of the reasons that reduces tool wear compared to conventional turning. Moreover, it has been shown that by increasing preheating temperature in hot turning, the hardness of the carbides in the workpiece decreases more than the hardness of the tool substrate and reduces coating materials, consequently reducing cutting tool abrasion wear phenomenon.

Cr2 O3 Promoted In2 O3 Catalysts for CO2 Hydrogenation to Methanol.

Cr2 O3 was applied to study the modification of In2 O3 based catalysts for CO2 hydrogenation to methanol reaction. Combined with X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS), etc., the structure of the catalysts was characterized. The reaction performances for CO2 hydrogenation to methanol were evaluated on a stainless-steel fix-bed reactor. The results showed that solid solutions were formed for the Cr2 O3 promoted In2 O3 catalysts. The important role of electronic interaction between Cr2 O3 and In2 O3 was revealed in the hydrogenation reaction. In1.25 Cr0.75 O3 sample exhibited the highest methanol yield, which was 2.8 times higher than that of pure In2 O3 . No deactivation was observed for In1.25 Cr0.75 O3 sample during the 50 hours of reaction. The improved catalytic performance may be due to the formation of the solid solutions and the highest amount of oxygen vacancies.

Enhanced adhesion and thermal stability of thick (Al,Cr)2O3 coatings on hot work steel

Al2O3 coatings deposited by chemical vapor deposition (CVD) at temperatures T ˃ 1000 °C are commonly used for wear and oxidation protection in manufacturing processes. Physical vapor deposition (PVD) gained also great interest to synthesize crystalline Al2O3 at lower temperatures by modification using Cr. High Speed PVD has the potential to synthesize thick crystalline (Al,Cr)2O3 coatings. However, previous studies showed that increasing adhesion strength is necessary for corresponding applications. This study evaluated various interlayer systems to enhance the adhesion strength between (Al,Cr)2O3 functional layer and steel X40CrMoV5-1. AlCrN interlayers of varying thicknesses were deposited, as well as two graded AlCrNg interlayers at different bias voltages. Afterwards, AlCrN/(Al,Cr)2O3 coatings were produced. Hereby, the functional layer thickness is varied. The AlCrNg/(Al,Cr)2O3 compounds show no spallation at the edge of Rockwell imprints and scratches at higher normal forces. The thermal stability of the coatings was investigated by annealing in vacuum at T = 1000 °C and T = 1200 °C. Moreover, no diffusion processes leading to chemical and structural changes was obtained after annealing. Therefore, thick (Al,Cr)2O3 coatings, s ≈ 30 μm, with a graded AlCrNg interlayer provide high potential for protecting hot-work steel against thermal loads up to T = 1200 °C.

Design and Construction of Carbon-Coated Fe3 O4 /Cr2 O3 Heterostructures Nanoparticles as High-Performance Anodes for Lithium Storage.

Transition metal oxides, highly motivated anodes for lithium-ion batteries due to high theoretical capacity, typically afflict by inferior conductivity and significant volume variation. Architecting heterogeneous structures with distinctive interfacial features can effectively regulate the electronic structure to favor electrochemical properties. Herein, an engineered carbon-coated nanosized Fe3 O4 /Cr2 O3 heterostructure with multiple interfaces is synthesized by a facile sol-gel method and subsequent heat treatment. Such ingenious components and structural design deliver rapid Li+ migration and facilitate charge transfer at the heterogeneous interface. Simultaneously, the strong coupling synergistic interactions between Fe3 O4 , Cr2 O3 , and carbon layers establish multiple interface structures and built-in electric fields, which accelerate ion/electron transport and effectively eliminate volume expansion. As a result, the multi-interface heterostructure, as a lithium-ion battery anode, exhibits superior cycling stability maintaining a reversible capacity of 651.2 mAh g-1 for 600 cycles at 2 C. The density functionaltheorycalculations not only unravel the electronic structure of the modulation but also illustrate favorable lithium-ion adsorption kinetics. This multi-interface heterostructure strategy offers a pathway for the development of advanced alkali metal-ion batteries.

Highly Active NiO-Ni(OH)2 -Cr2 O3 /Ni Hydrogen Evolution Electrocatalyst through Synergistic Reaction Kinetics.

High activity catalysts for hydrogen evolution reaction (HER) play a key role in converting renewable electricity to storable hydrogen fuel. Great effort has been devoted to the search for noble metal free catalysts to make electrolysis viable for practical applications. Here, a non-precious metal oxide/metal catalyst with high intrinsic activity comparable to Pt/C was reported. The electrocatalyst consisting of NiO, Ni(OH)2 , Cr2 O3 , and Ni metal exhibits a low overpotential of 27, 103, and 153 mV at current densities of 10, 100, and 200 mA cm-2 , respectively, in a 1.0 m NaOH electrolyte. The activity is much higher than that of NiOx /Ni or Cr2 O3 alone, showing the synergistic effect of NiOx /Ni and Cr2 O3 on catalyzing HER. Density functional theory calculations shows that NiO and Cr2 O3 on Ni surface lower the disassociation energy barrier for breaking H-OH bond, while Ni(OH)2 and Cr2 O3 create preferred sites on Ni surface with near-zero H* adsorption free energy to promote H* to gaseous H2 evolution. These synergistic effects of multiple-oxides/metal composition enhance the disassociation of H-OH and the evolution of H* to gaseous H2 , thus achieving high activity and demonstrating a promising composition design for noble metal free catalyst.