Electrocatalytic generation and tuning of ultra-stable and ultra-dense nanometre bubbles: an in situ molecular dynamics study

Gas Evolution in Water Electrolysis

Gas bubbles generated by the hydrogen evolution reaction and oxygen evolution reaction during water electrolysis influence the energy conversion efficiency of hydrogen production. Here, we survey what is known about the interaction of gas bubbles and electrode surfaces and the influence of gas evolution on practicable devices used for water electrolysis. We outline the physical processes occurring during the life cycle of a bubble, summarize techniques used to characterize gas evolution phenomena in situ and in practical device environments, and discuss ways that electrodes can be tailored to facilitate gas removal at high current densities. Lastly, we review efforts to model the behavior of individual gas bubbles and multiphase flows produced at gas-evolving electrodes. We conclude our review with a short summary of outstanding questions that could be answered by future efforts to characterize gas evolution in electrochemical device environments or by improved simulations of multiphase flows.

Solar Energy Storage in an All-Vanadium Photoelectrochemical Cell: Structural Effect of Titania Nanocatalyst in Photoanode

Solar energy storage in the form of chemical energy is considered a promising alternative for solar energy utilization. High-performance solar energy conversion and storage significantly rely on the sufficient active surface area and the efficient transport of both reactants and charge carriers. Herein, the structure evolution of titania nanotube photocatalyst during the photoanode fabrication and its effect on photoelectrochemical activity in a microfluidic all-vanadium photoelectrochemical cell was investigated. Experimental results have shown that there exist opposite variation trends for the pore structure and crystallinity of the photocatalyst. With the increase in calcination temperature, the active surface area and pore volume were gradually declined while the crystallinity was significantly improved. The trade-off between the gradually deteriorated sintering and optimized crystallinity of the photocatalyst then determined the photoelectrochemical reaction efficiency. The optimal average photocurrent density and vanadium ions conversion rate emerged at an appropriate calcination temperature, where both the plentiful pores and large active surface area, as well as good crystallinity, could be ensured to promote the photoelectrochemical activity. This work reveals the structure evolution of the nanostructured photocatalyst in influencing the solar energy conversion and storage, which is useful for the structural design of the photoelectrodes in real applications.