Structure regulation of CoSe2 and sulfur-containing wastewater degradation and photocatalytic water splitting with simultaneous contaminant degradation
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摘要: 光催化技术绿色环保,近年来在氢能开发、污染净化、医疗保健等领域具有一定的应用前景,有望成为解决环境和能源问题的有效途径。通过控制煅烧条件成功转变相结构,制备了两种不同晶相结构的硒化钴(CoSe2),即正交相硒化钴(o-CoSe2)与立方相硒化钴(c-CoSe2)。选择半导体CdS进行复合,发现两种助催化剂均对光催化降解及制氢有良好的促进作用。通过莫特肖特基曲线(MS)、固体紫外吸收光谱(UV-vis DRS)、稳态荧光光谱(PL)和光电性能表征发现c-CoSe2比o-CoSe2具有更强的导电性及更高效的电荷传输能力,这理论上更利于光催化反应的进行。以乳酸为牺牲剂,o-CoSe2质量分数为10wt%的o-CoSe2/CdS和c-CoSe2质量分数为10wt%的c-CoSe2/CdS为最优负载量的制氢效率分别为9006.2 μmol·g−1·h−1和7151.2 μmol·g−1·h−1,较CdS单体而言分别提升了20倍和15倍,接近甚至超过了同条件下贵金属铂(Pt)负载的制氢活性。最优负载o-CoSe2质量分数为10wt%的o-CoSe2/CdS在含硫废水亚甲基蓝(MB)降解及协同产氢测试中兼顾了降解和产氢性能。结合光催化反应步骤及理论计算分析,发现o-CoSe2金属钴位点上有更合适的氢吸附自由能,是其具有最佳助催效果的关键原因。Abstract: Photocatalytic technology, due to its green and environmental friendliness, has a certain application prospect in the fields of hydrogen energy development, pollution purification and medical care in recent years. To explore the influence of the cocatalyst on the performance of hydrogen production, the crystal structure of the cocatalyst itself is studied. The phase structure was successfully transformed by controlling the calcination conditions, and two different crystal phase structures of cobalt selenide (CoSe2) were prepared, namely orthogonal cobalt selenide (o-CoSe2) and cubic cobalt selnide (c-CoSe2). The semiconductor CdS semiconductor was chosen for recombination, and found that the two promoters both have a good promoting effect on the photocatalytic hydrogen production. Through Motschottky curve (MS), UV-vis diffuse reflectance spectra (UV-vis DRS), fluorescence (PL) and photoelectric performance characterization, c-CoSe2 has stronger conductivity and more efficient charge transport ability than o-CoSe2, which is theoretically more conducive to the photocatalytic reaction. With lactic acid as the sacrificial agent, the optimal loading of 10wt%o-CoSe2/CdS and 10wt%c-CoSe2/CdS hydrogen production efficiencies are 9006.2 μmol·g−1·h−1 and 7151.2 μmol·g−1·h−1, respectively. In general, it has been increased by 20 times and 15 times respectively, which is close to or even surpassing the hydrogen production activity supported by the precious metal platinum (Pt) under the same conditions. The degradation and hydrogen production of 10wt%o-CoSe2/CdS are achieved in photocatalytic degradation simultaneous with hydrogen evolution. Combining the steps of the photocatalytic reaction and theoretical calculation and analysis, it is found that the more suitable free energy of hydrogen adsorption on the cobalt site of o-CoSe2 is the key reason for its use as a better hydrogen production co-catalyst.
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Key words:
- CoSe2 /
- crystal phase engineering /
- photocatalysis /
- hydrogen production /
- degradation /
- methylene blue (MB)
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图 1 o-CoSe2和c-CoSe2的XRD图谱 (a) 和拉曼光谱 (b);CdS、10wt%o-CoSe2/CdS和10wt%c-CoSe2/CdS的XRD图谱 (c) 和氮气吸附-脱附曲线 (d)
Figure 1. XRD patterns (a) and Raman spectra (b) of o-CoSe2 and c-CoSe2; XRD patterns (c) and N2 adsorption-desorption curves (d) of CdS, 10wt%o-CoSe2/CdS and 10wt%c-CoSe2/CdS
STP—Standard temperature and pressure
图 3 o-CoSe2的SEM图像 (a)、TEM图像 (b)、HRTTEM图像(插图为电子衍射图) (c);c-CoSe2的SEM图像 (d)、TEM图像 (e)、HRTTEM图像(插图为电子衍射图) (f);CdS、10wt%o-CoSe2/CdS、10wt%c-CoSe2/CdS的SEM图像 ((g)~(i))
Figure 3. SEM image (a), TEM image (b), HRTEM image (Inset is electron diffraction pattern) (c) of o-CoSe2; SEM image (d), TEM image (e), HRTEM image (Inset is electron diffraction pattern) (f) of c-CoSe2; SEM images of CdS, 10wt%o-CoSe2/CdS and 10wt%c-CoSe2/CdS ((g)-(i))
d—Spacing
图 5 (a) CdS、10wt%o-CoSe2/CdS和10wt%c-CoSe2/CdS样品的瞬时光电流图谱;(b) 10wt%o-CoSe2/CdS和10wt%c-CoSe2/CdS样品的电化学阻抗谱;(c) 不同样品的莫特肖特基曲线
Figure 5. (a) Transient photocurrent curves of CdS, 10wt%o-CoSe2/CdS and 10wt%c-CoSe2/CdS; (b) Electrochemical impedance spectroscopy of 10wt%o-CoSe2/CdS and 10wt%c-CoSe2/CdS; (c) Motshottky curves of different samples
Z'—Real impedance; Z''—Imaginary impedance; 1/C2—Reciprocal of the capacitance squared
图 4 CdS、o-CoSe2/CdS、c-CoSe2/CdS (a) 和o-CoSe2、c-CoSe2 (b) 的UV-vis DRS光谱;(c) CdS的带隙评估图;(d) o-CoSe2/CdS和c-CoSe2/CdS在370 nm处的PL光谱
Figure 4. UV-vis DRS of CdS, o-CoSe2/CdS, c-CoSe2/CdS (a) and o-CoSe2, c-CoSe2 (b); (c) Estimated bandgap of CdS; (d) PL spectra excited at 370 nm of o-CoSe2/CdS and c-CoSe2/CdS
图 6 (a) CdS、5wt%、10wt%和15wt%o-CoSe2/CdS样品的光催化制氢性能比较;(b) 10%o-CoSe2/CdS样品的制氢稳定性试验;(c) CdS、5wt%、10wt%和15wt%c-CoSe2/CdS样品的光催化制氢性能比较;(d) 10wt%c-CoSe2/CdS样品的制氢稳定性试验;(e) 在不同波长下10wt%c-CoSe2/CdS和10%o-CoSe2/CdS样品的量子效率图(AQY)(10wt%乳酸作为牺牲剂,50 mg催化剂,带UV滤光片氙灯作为光源,420~850 nm)
Figure 6. (a) Photocatalytic hydrogen evolution reaction performance of CdS, 5wt%, 10wt% and 15wt%o-CoSe2/CdS; (b) Stability test of 10wt%o-CoSe2/CdS; (c) Photocatalytic hydrogen evolution reaction performance of CdS, 5wt%, 10wt% and 15wt%c-CoSe2/ CdS; (d) Stability test of 10wt%c-CoSe2/CdS; (e) Apparent quantum yield (AQY) of 10wt%c-CoSe2/CdS and 10wt%o-CoSe2/CdS under different wavelength (10wt% C3H6O3 as sacrificial agent, 50 mg catalyst usage, a xenon lamp as a light source, 420-850 nm)
图 7 (a) CdS、10wt%o-CoSe2/CdS、10wt%c-CoSe2/CdS和1wt%Pt/CdS样品的光催化制氢性能比较;(b) 10wt%o-CoSe2/CdS降解MB协同产氢量图; (c) CdS、10wt%o-CoSe2/CdS和10wt%c-CoSe2/CdS降解MB性能图;(d) 10wt%o-CoSe2/CdS降解不同浓度的MB 4 h协同产氢量图;10wt%c-CoSe2/CdS (e) 和10wt%o-CoSe2/CdS (f) 循环后的XRD图谱
Figure 7. (a) Photocatalytic hydrogen evolution reaction performance of CdS, 10wt%o-CoSe2/ CdS, 10wt%c-CoSe2/CdS and 1wt%Pt/CdS; (b) Photocatalytic degradation simultaneous with hydrogen evolution reaction of 10wt%o-CoSe2/CdS; (c) Photodegradation of MB of CdS, 10wt%o-CoSe2/ CdS, 10wt%c-CoSe2/CdS; (d) Effect of concentration of the photocatalytic degradation simultaneous with HER system of 10wt%o-CoSe2/CdS after 4 h; XRD patterns of 10wt%c-CoSe2/CdS (e) and 10wt%o-CoSe2/CdS (f) before and after the cycle
C—Concentration; C0—Initial concentration
表 1 o-CoSe2/CdS和c-CoSe2/CdS的命名
Table 1. Naming of o-CoSe2/CdS and c-CoSe2/CdS
Sample o-CoSe2/wt% c-CoSe2/wt% CdS/wt% 5wt%o-CoSe2/CdS 5 - 95 10wt%o-CoSe2/CdS 10 - 90 15wt%o-CoSe2/CdS 15 - 85 5wt%c-CoSe2/CdS - 5 95 10wt%c-CoSe2/CdS - 10 90 15wt%c-CoSe2/CdS - 15 85 -
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