Semiconducting Hetero-Nanostructures with Novel Configurations for Photoelectrochemical Water Splitting

Subramanyam, Palyam and Ch, Subrahmanyam (2020) Semiconducting Hetero-Nanostructures with Novel Configurations for Photoelectrochemical Water Splitting. PhD thesis, Indian Institute of Technology Hyderabad.

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Abstract

Energy production and environmental pollution are the two major problems the world is facing today. The depletion of fossil fuels and the emission of harmful gases into the atmosphere lead the research on clean and renewable energy sources. In this context, hydrogen is considered as an ideal fuel for meeting the global energy needs. However, at present hydrogen is produced from fossil fuels, whereas the most desirable way is to produce it from clean and renewable energy sources, like water. Similarly, sunlight is an abundant energy source for energy harvesting and utilization. Recent studies reveal that photoelectrochemical (PEC) water splitting has promise for solar to hydrogen (STH) conversion than the widely tested photocatalytic approach, as hydrogen and oxygen gases can be easily separated in PEC. Semiconductors are the primary choice of the light-absorbing materials, which undergo excitation upon solar light irradiation to produce excitons (electron-hole pairs) to drive the electrolysis. Visible light active semiconductors are attractive to achieve high solar to chemical fuel conversion. However, pure semiconductor materials are far for practical applications due to either charge carrier recombination, poor light-harvesting and/or electrodes degradation. To overcome these issues, various attempts have been made to develop unique hetero-nanostructures with the integration of metal plasmons and/or suitable semiconducting materials. • This work aims to develop semiconducting hetero-nanostructures with novel configurations for photoelectrochemical water splitting. Various anodic materials were successfully synthesized, systematically characterized and used for hydrogen evolution. The significant findings are summarized as follows: • In general, the heterojunction systems suppress the charge carrier recombination and enhance the charge carrier lifetime for PEC water-splitting. • Metal oxides (BiVO4) and metal sulfides (Bi2S3) based-hetero-nanostructures have shown promise for PEC water splitting. • Mo-dopant improves charge carrier density and transportation in BiVO4 and hence higher PEC performance than BiVO4. • Integrating rGO with BiVO4 improves PEC activity due to higher electrical conductivity and facile charge transportation to the counter electrode. • Decoration of plasmonic noble or non-noble metal nanoparticles on photoelectrodes enhances the light absorption property and also reduces the recombination of photogenerated charge carriers.

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