The increased environmental pollution caused by gargantuan fossil-fuel consumption has necessitated approaches targeting efficient use of energy while also exploring the use of clean and non-carbonaceous fuel to address the incessant global energy demand. ¹  Hydrogen, being the most lightweight fuel has the ability to provide clean, reliable and affordable energy supply without any greenhouse gas emission while also having the potential to meet the global energy demand. However, efficient and economic production of hydrogen, along with cost effective storage and distribution are the major bottlenecks impeding the commercial development of hydrogen as a fuel requiring to be addressed.^2-4 Among all promising renewable energy sources, solar energy remains a highly attractive resource since it represents essentially a de-concentrated and an inexhaustible energy source. Hence, solar energy driven water splitting, also known as photo-electrochemical (PEC) water splitting is an attractive and constitutes a highly promising approach for economic and efficient hydrogen production, since water splitting does not involve any greenhouse gas emission or any toxic byproducts.⁵

The development of semiconductor materials for use as photoanodes with superior optoelectronic properties along with excellent photoelectrochemical activity and stability is extremely important for the commercial development of PEC water splitting. Thus far, semiconductor materials such as TiO₂, ZnO have been identified but suffer from issues of wide band gap and poor stability for long term PEC water splitting operation. In this study, bilayer nanotubes (NTs) of transition metal oxide carefully selected and appropriately co-doped with conducting metal oxides, are engineered to be explored as potential semiconductor materials for use as photoanodes in PEC water splitting. The cross-sectional SEM image of the engineered bilayer system is shown in Fig. 1.

The photoelectrochemical characterization has been carried out in 0.5 M H₂SO₄ as an electrolyte, Hg/Hg₂SO₄ as the reference electrode (+0.65 V vs. NHE), using a scan rate of 10 mV/sec and temperature of 26^oC in an H-type cell, where the engineered novel photoanode and cathode (Pt/C) are separated by Nafion membrane. The results of the synthesis, microstructural and robust long-term photoelectrochemical activity of these novel engineered semiconductor materials will be presented and discussed.

References:

1. P. P. Patel, P. H. Jampani, M. K. Datta, O. I. Velikokhatnyi, D. Hong, J. A. Poston, A. Manivannan and P. N. Kumta, Journal of Materials Chemistry A, 2015, 3, 18296-18309.

2. P. P. Patel, P. J. Hanumantha, O. I. Velikokhatnyi, M. K. Datta, D. Hong, B. Gattu, J. A. Poston, A. Manivannan and P. N. Kumta, Journal of Power Sources, 2015, 299, 11-24.

3. P. P. Patel, M. K. Datta, O. I. Velikokhatnyi, P. Jampani, D. Hong, J. A. Poston, A. Manivannan and P. N. Kumta, Journal of Materials Chemistry A, 2015, 3, 14015-14032.

4. P. P. Patel, M. K. Datta, P. H. Jampani, D. Hong, J. A. Poston, A. Manivannan and P. N. Kumta, Journal of Power Sources, 2015, 293, 437-446.

5. S. Grigoriev, V. Porembsky and V. Fateev, International Journal of Hydrogen Energy, 2006, 31, 171-175.