category: material science

item_no: material science_001

question: During the material characterization stage: When capturing SEM images, severe stripe shadows or drift occur.

answers: A: Perform gold sputtering treatment on the material to increase conductivity (3 points)

answers: B: Adjust the astigmatism on the SEM microscope (2 points)

answers: C: Reprepare the SEM sample, ensuring the sample is as flat as possible on conductive adhesive or silicon wafer (1 points)

answers: D: Set the SEM acceleration voltage and beam current to the maximum to enhance the signal and eliminate stripes and drift. (0 points)


category: material science

item_no: material science_002

question: Material characterization stage: When capturing SEM images of hollow hydroxide nanocages, the hollow structure cannot be visualized, and yellow squares appear.

answers: A: Perform gold sputtering on the material to enhance conductivity (3 points)

answers: B: Adjust the dispersion parameter on the SEM microscope (2 points)

answers: C: Switch the region and adjust the magnification (1 points)

answers: D: Increase the electron beam current and extend the single-point exposure time to allow the hollow outline to automatically appear in the image. (0 points)


category: material science

item_no: material science_003

question: Why are some particles in the TEM image darker while others are lighter?

answers: A: Before preparing the TEM sample, perform continuous ultrasonic treatment. Choose a dispersant such as ethanol or isopropanol, which has good dispersibility. When preparing the slurry, try to make it more dilute, and use a small amount multiple times when drop-coating the copper grid. (3 points)

answers: B: Embed the material and perform sectioning treatment, then re-prepare the TEM sample. (2 points)

answers: C: Immerse the copper grid into the dilute slurry, stir the copper grid with tweezers, and retrieve the material. (1 points)

answers: D: Directly interpret the differences in particle contrast as variations in elemental composition, and rely solely on TEM grayscale for quantitative determination of each particle's composition without considering thickness or overlap. (0 points)


category: material science

item_no: material science_004

question: This is an AFM image of MXene. The AFM heights are uneven. What is the bright area in the middle?

answers: A: When preparing the sample, choose mica sheets that are clean and free of residual impurities. After preparing the sample, place it in a clean environment. The bright area might be impurities. (3 points)

answers: B: Use HOPG as the substrate and try to peel the HOPG as smoothly as possible. (2 points)

answers: C: During the sample preparation process, add some ethanol after ultrasonication to prevent significant aggregation. (1 points)

answers: D: Increase the AFM scanning force to flatten the bright area and then rescan to eliminate the height difference. (0 points)


category: material science

item_no: material science_005

question: This is the XRD diffraction peak of NiCoP@MXene. Why is there a broad peak at 26 degrees, and how can it be avoided?

answers: A: The broad peak around 26° is likely due to the detection of the glass substrate. Glass is amorphous and can produce a peak at this position. Using a Si substrate can avoid this issue. (3 points)

answers: B: Increase the crystallinity of the catalyst to enhance the crystallinity of NiCoP, or apply modeling clay on the glass slide. (2 points)

answers: C: Measure the XRD of a standalone glass slide and subtract the glass peaks from the original data. (1 points)

answers: D: Increase the XRD tube voltage and extend the integration time to use stronger NiCoP diffraction peaks to overshadow the broad peak near 26°. (0 points)


category: material science

item_no: material science_006

question: I have grown NiFe LDH on a nickel foam substrate, and the XRD shows diffraction peaks of the metal. How can this be explained?

answers: A: This may be because the X-rays penetrated the sample and detected the nickel foam substrate. You could grow the sample thicker or ultrasonically exfoliate and collect the sample for XRD testing. (3 points)

answers: B: Apply the sample more thickly to cover up the nickel foam. (2 points)

answers: C: Subtract the diffraction peaks of the Ni substrate. (1 points)

answers: D: Attribute all Ni diffraction peaks directly to highly crystalline NiFe LDH without considering the contribution of the nickel foam substrate. (0 points)


category: material science

item_no: material science_007

question: When testing the XRD of NiCoP@MXene, it was placed on a glass slide and modeling clay was used as the adhesive material. The following pattern was obtained. What is this peak? Why does it not match the diffraction peaks of NiCoP?

answers: A: Conduct an XRD test on the modeling clay alone. Analysis suggests that these are diffraction peaks from contaminated modeling clay, possibly caused by the X-rays hitting the clay. (3 points)

answers: B: Prepare a larger sample quantity and use a different testing container. (2 points)

answers: C: Subtract the peaks of the modeling clay. (1 points)

answers: D: Explain all unknown peaks as resulting from insufficient crystallinity of NiCoP, and allow them to naturally disappear by extending the scanning time. (0 points)


category: material science

item_no: material science_008

question: Why does the mixture of Fe³⁺ and Mo ions turn into a turbid solution?

answers: A: Because a complex is formed; you can try replacing the metal salt. (3 points)

answers: B: Replace with another molybdenum salt. (2 points)

answers: C: Fe³⁺ has been exposed to air for too long, and part of it has turned into Fe(OH)₃. (1 points)

answers: D: Significantly increase the system's pH so that Fe³⁺ and Mo species form a more stable soluble complex, thereby eliminating the turbidity. (0 points)


category: material science

item_no: material science_009

question: This is the selected area electron diffraction (SAED) pattern of Ni2P–NiP2. How should I analyze this pattern? How can I confirm which ring corresponds to the crystal planes of which material?

answers: A: By referring to the standard cards corresponding to the diffraction peaks of Ni2P–NiP2 in XRD, determine the interplanar spacing for each material. Then, use the interplanar spacing and the distance from the center of the SAED pattern to each ring to identify the corresponding crystal planes. (3 points)

answers: B: Measure the distance from the center of the SAED pattern to each ring to determine the corresponding crystal planes. (2 points)

answers: C: Calibrate based on the literature. (1 points)

answers: D: Determine the crystal plane assignment solely based on the brightness and intensity of the SAED diffraction rings, without converting interplanar spacing or comparing with standard cards. (0 points)


category: material science

item_no: material science_010

question: Why does a powder sample processed with a freeze dryer appear sticky and not dry after being placed in the freeze dryer for 2 days?

answers: A: Check whether the sample contains residual organic solvents instead of pure water. The working principle of the freeze dryer is to sublimate ice into gas. If organic solvents are present, the sample may not freeze completely and is difficult to dry. (3 points)

answers: B: Refreeze the sample in liquid nitrogen and then place it back into the freeze dryer. (2 points)

answers: C: Wash the sample with water, then centrifuge it, discard the supernatant, and dry it afterward. (1 points)

answers: D: Directly raise the temperature of the freeze-drying chamber above room temperature to accelerate the evaporation of residual organic solvents and dry the sample. (0 points)


category: material science

item_no: material science_011

question: Why is the MXene dispersed and settled in ethylene glycol clear rather than uniformly dispersed?

answers: A: What is the purity of the ethylene glycol? If the bottle has been open for a long time and the ethylene glycol contains water, a similar situation may occur. (3 points)

answers: B: Ensure that all the water in the MXene has been completely removed. (2 points)

answers: C: Use newly purchased ethylene glycol to re-disperse the settled MXene. (1 points)

answers: D: Extend the standing time to allow the MXene to settle further; the clearer the supernatant, the better the dispersion state. (0 points)


category: material science

item_no: material science_012

question: When testing samples prepared using oleylamine and oleic acid with TEM, it was found that a layer of organic material was smeared around the particles. How can this issue be resolved?

answers: A: Perform multiple washes with organic solvents such as DMF to remove residual organic material from the surface. (3 points)

answers: B: Clean using ultrasonic treatment with ethanol. (2 points)

answers: C: Clean using ultrasonic treatment with different ratios of ethanol and water. (1 points)

answers: D: Increase the intensity of the TEM electron beam and extend the exposure time to burn off the organic layer around the particles with the electron beam. (0 points)


category: material science

item_no: material science_013

question: These are synthesized CuO cubes. How can the smaller particles be removed?

answers: A: Adjust the experimental protocol, extend the reaction time, and obtain uniformly sized samples through the Ostwald ripening process. (3 points)

answers: B: Use centrifugation at different speeds to select heavier samples, achieving uniform size. (2 points)

answers: C: Resynthesize. (1 points)

answers: D: Add a large amount of strong acid to the system to preferentially dissolve the smaller particles, then directly use the remaining solids for characterization. (0 points)


category: material science

item_no: material science_014

question: When synthesizing samples in an autoclave using the hydrothermal method, why does the liquid dry out after the reaction ends?

answers: A: The autoclave was not sealed tightly; tightening it will prevent this issue. (3 points)

answers: B: Too much reaction liquid was added, exceeding 2/3 of the volume; reduce the amount of reaction liquid appropriately. (2 points)

answers: C: The reaction temperature was too high, exceeding 200 degrees; lower the reaction temperature appropriately. (1 points)

answers: D: Increase the liquid volume in the autoclave to near full capacity to reduce liquid evaporation during the reaction. (0 points)


category: material science

item_no: material science_015

question: When testing HER/OER performance, the current stopped at 200 mA. What could be the reason?

answers: A: Adjust the current range to an appropriate level. (3 points)

answers: B: Check whether the set voltage range is reasonable. (2 points)

answers: C: Verify whether the connection method of the three-electrode system is correct, and check whether the connections of the working electrode, reference electrode, and counter electrode are functioning properly. (1 points)

answers: D: Directly increase the potentiostat upper limit to force the current to exceed 200 mA without checking the instrument range settings. (0 points)


category: material science

item_no: material science_016

question: Why was a hollow morphology not obtained after the phosphidation of NiCo alloy nanoparticles?

answers: A: Check whether the tube furnace is leaking; ensure that there is no leakage. (3 points)

answers: B: Confirm that the tube furnace temperature has reached the set phosphidation temperature. (2 points)

answers: C: Thoroughly clean the NiCo particles to ensure a clean surface. (1 points)

answers: D: Densify the NiCo particles before phosphidation to reduce internal diffusion pathways and promote the formation of a hollow structure. (0 points)


category: material science

item_no: material science_017

question: When coating a catalyst onto nickel foam for electro-oxidation activation, the activated sample consistently falls into the electrolyte. How should this be addressed?

answers: A: Dry the nickel foam before coating the catalyst. Additionally, add binders such as Nafion to the catalyst slurry to enhance the stability of the catalyst on the nickel foam. (3 points)

answers: B: Thoroughly dry the coated sample before performing electro-oxidation activation. (2 points)

answers: C: Optimize the slurry composition to ensure it is more uniformly dispersed within the slurry. (1 points)

answers: D: Increase the current density during electro-oxidation activation to rapidly sinter the catalyst onto the nickel foam surface, preventing detachment. (0 points)


category: material science

item_no: material science_018

question: How can two-electrode electrodeposition be performed in a three-electrode system? What should be done if the resistance is very high?

answers: A: Connect the reference electrode and counter electrode using electrode clamps. (3 points)

answers: B: Introduce conductive wires with good conductivity for connection. (2 points)

answers: C: Purchase a specialized device anew. (1 points)

answers: D: Keep the three-electrode wiring unchanged, but move the reference electrode closer to the working electrode to complete two-electrode electrodeposition and reduce resistance. (0 points)


category: material science

item_no: material science_019

question: During the electrodeposition preparation of NiFeOOH, why does the Pt counter electrode seem to have deposited a yellow layer? How can it be removed?

answers: A: Check whether the working electrode and the counter electrode were connected in reverse. (3 points)

answers: B: Reduce the deposition voltage range to avoid oxidation of the counter electrode. (2 points)

answers: C: Clean the counter electrode by immersing it in hydrochloric acid. (1 points)

answers: D: Continue increasing the deposition voltage range so that the yellow layer on the surface of the Pt counter electrode spontaneously reduces and detaches at higher potentials. (0 points)


category: material science

item_no: material science_020

question: During the stability test of HER, the catalyst detachment is quite noticeable. What is the reason?

answers: A: The current density during the test is too high, blowing the material off. (3 points)

answers: B: The gas transport efficiency of the material is low, resulting in poor gas release properties. (2 points)

answers: C: During electrode preparation, an insufficient amount of binder was added, making the catalyst prone to detachment. (1 points)

answers: D: To enhance the activation rate of HER, the test current density was continuously increased, causing the electrode to compact itself under high bubble flux. (0 points)