Cu and Pt loaded TiO₂ for H₂ production via photocatalytic ethanol reforming

Research for my chemical engineering master's degree investigating whether Cu/TiO₂ has the potential to be a low-cost alternative to Pt/TiO₂ for hydrogen production via photocatalytic ethanol reforming.

The copper-loaded and platinum-loaded TiO₂ photocatalysts were synthesised using the experimental methods developed by Zhang et al. (2017), Jiang et al. (2015), and Fontelles-Carceller et al. (2017).

The bare, copper-loaded, and platinum-loaded TiO₂ photocatalysts were characterised using the analytical equipment available at Stellenbosch University's Department of Chemistry and the Technical University of Munich's Department of Chemistry.

Finally, the experimental hydrogen yields and selectivities of the bare, copper-loaded, and platinum-loaded TiO₂ photocatalysts were measured at the Technical University of Munich's Chair for Physical Chemistry using the ambient-pressure liquid-phase photoreactor developed by Aletsee et al. (2023).

Resources

• The synthesis folder contains the MATLAB live script used for calculating the required chemical masses to use during the synthesis procedure, the drs folder contains the MATLAB live script used for processing the diffuse reflectance spectroscopy (DRS) data in order to calculate the Kubelka-Munk functions of the samples, and the anova folder contains the MATLAB Live Script used for performing a one-way analysis of variance (ANOVA) to determine whether the differences in the measured photocatalytic yields are statistically significant.

• Intructions.md contains instructions for running the synthesis Live Script; information regarding the nomenclature of the bare, copper-loaded, and platinum-loaded TiO₂ photocatalyst samples; information regarding the colour scheme used to represent the different TiO₂ photocatalysts; and instructions for running the DRS and ANOVA Live Scripts.

• The photocatalysis folder contains the Excel workbook used for calculating the hydrogen yields and selectivities of the bare, copper-loaded, and platinum-loaded TiO₂ photocatalysts, while the calibration folder contains the Excel workbook used for calibrating the photocatalytic hydrogen yields.

• The results folder contains all of the experimental results for the synthesis of the copper-loaded and platinum-loaded TiO₂ photocatalysts; the characterisation of the bare, copper-loaded, and platinum-loaded TiO₂ photocatalysts' physical, compositional, morphological, crystallographic, and optical properties; and the measurement of their photocatalytic hydrogen yields and selectivities.

Results

The photocatalytic hydrogen yields of the bare, copper-loaded, and platinum-loaded TiO₂ photocatalysts are plotted in Figure 1a, while the specific photocatalytic hydrogen production rates are plotted in Figure 1b. The photocatalytic yields of each TiO₂ photocatalyst were measured in triplicate, and the average values were plotted, while the error bars represent the standard deviations.

Figure 1: The (a) photocatalytic hydrogen yields and (b) photocatalytic hydrogen production rates of the bare, copper-loaded, and platinum-loaded TiO₂ photocatalysts.

Figure 1 reveals that all three copper-loaded TiO₂ photocatalysts produced about the same amount of hydrogen and that both platinum-loaded TiO₂ photocatalysts produced about the same amount of hydrogen, with the platinum-loaded TiO₂ photocatalysts producing about 3 times more hydrogen than the copper-loaded TiO₂ photocatalysts did.

Figure 1 also reveals that the bare TiO₂ photocatalyst was unable to produce any hydrogen, confirming that the hole-mediated disproportionation mechanism proposed by Eder et al. (2023) and Walenta et al. (2019a) based on their ultra-high vacuum (UHV) studies is also valid for ambient-pressure liquid-phase heterogeneous photocatalytic systems.

At the time of purchase, the copper atoms sourced from CuCl₂ had a price of R64.02 per gram copper while the platinum atoms sourced from H₂PtCl₆ • 𝑥H₂O had a price of R6 640.16 per gram platinum. Therefore, even though the platinum-loaded TiO₂ photocatalysts were able to produce about 3 times more hydrogen than the copper-loaded TiO₂ photocatalyst could, the platinum atoms cost about 100 times more than the copper atoms did.

Similarly, at the time of writing, copper traded for $4.07 per pound, while platinum traded for $942.00 per troy ounce, corresponding to $13 737.51 per pound. At the industrial scale, the platinum-loaded TiO₂ photocatalysts would therefore cost about 3 400 times more than the copper-loaded TiO₂ photocatalysts would. Combined, these results suggest that copper loading has the potential to be a low-cost alternative to platinum loading for the production of green hydrogen via photocatalytic ethanol reforming.

References

Aletsee, C., Tschurl, M., Heiz, U., 2023. Liquid phase setup design. Technical University of Munich, Garching bei München.

Eder, M., Tschurl, M., Heiz, U., 2023. Toward a Comprehensive Understanding of Photocatalysis: What Systematic Studies and Alcohol Surface Chemistry on TiO2(110) Have to Offer for Future Developments. Journal of Physical Chemistry Letters 14, 6193–6201. https://doi.org/10.1021/ACS.JPCLETT.3C00504

Fontelles-Carceller, O., Muñoz-Batista, M.J., Rodríguez-Castellón, E., Conesa, J.C., Fernández-García, M., Kubacka, A., 2017. Measuring and interpreting quantum efficiency for hydrogen photo-production using Pt-titania catalysts. J Catal 347, 157–169. https://doi.org/10.1016/J.JCAT.2017.01.012

Jiang, Z., Zhang, Z.Y., Shangguan, W., Isaacs, M.A., Durndell, L.J., Parlett, C.M.A., Lee, A.F., 2015. Photodeposition as a facile route to tunable Pt photocatalysts for hydrogen production: on the role of methanol. Catal Sci Technol 6, 81–88. https://doi.org/10.1039/C5CY01364J

Walenta, C.A., Kollmannsberger, S.L., Courtois, C., Pereira, R.N., Stutzmann, M., Tschurl, M., Heiz, U., 2019. Why co-catalyst-loaded rutile facilitates photocatalytic hydrogen evolution. Physical Chemistry Chemical Physics 21, 1491–1496. https://doi.org/10.1039/C8CP05513K

Zhang, M., Pei, Q., Chen, W., Liu, L., He, T., Chen, P., 2017. Room temperature synthesis of reduced TiO2 and its application as a support for catalytic hydrogenation. RSC Adv 7, 4306–4311. https://doi.org/10.1039/C6RA26667C