Advanced Nanostructured Electrodes for Solar Fuel Conversion

Photoelectrochemical (PEC) water splitting and electrochemical hydrogen evolution reaction (HER) appear to be key technological components of a hydrogen-based economy which may secure sustainable energy future. Nevertheless, several limitations of PEC cell and HER electrode materials is still present. Modification of semiconductor materials bearing narrow band gap for visible spectrum, high solar to hydrogen conversion efficiency and high stability for efficient PEC cell is required for futures commercially applicable energy conversion systems. Besides, development of cost effective non-noble metal electrocatalysts with remarkable electrocatalytic efficiency for HER to overcome the limitations of high cost noble platinum (Pt)-group materials, is necessary en route to profitable and efficient water splitting devices. Thereupon, firstly we employed plasmonic nanoparticles combined with semiconductor to confine light absorption locally in active layer of semiconductor. These nanophotonic structures can generate surface plasmon resonances (SPR) which will act light antennas and localize electromagnetic radiation energy near the active surface layer. Accordingly, core@shell and core@shell@shell nanoparticles were implemented to modify PEC performance of BiVO4 photoanode. In this regard, the heterostructure offered improved light absorption, higher catalytic efficiency and efficient separation and transport of photogenerated charge carriers leading to improved PEC cell efficiency. Furthermore, metal chalcogenide sensitized SnO2 nanowire based heteronanostructured systems tested as an active photoanode material for PEC cell. Highly conductive SnO2 nanowire arrays has been fabricated and different sensitization methods has been used on these photoelectrodes. The novel photoelectrode exhibits panchromatic light absorption capability, low thermalization loss, and improved photogenerated charge carrier transport behavior, providing improved photocurrent density PEC cell system. Lastly, Mo2C and Mo2C-GO electrocatalysts have been fabricated using in situ growth, microwave assisted, facile preparation method. Electrocatalytic activities were studied as a cathode for HER. Mo2C-GO nanocomposites provide enhanced electronic conductivity, reduced particle size, more electrocatalytic active sites, improved structural stability. Hence, molybdenum-based electrocatalysts are promising non-noble, cost-effective, conductive, catalytically active alternatives to noble Pt group electrocatalysts. Overall, this dissertation study provides a detailed study to shed light into the rational design of advanced nanostructured PEC photoanodes and HER catalysts, and systematic study of synthesis, characterization, photoelectrochemical and electrochemical activities of the resultant photoanodes and cathodes.