Abstract
A controllable generation of oxygen gas during the decomposition of hydrogen peroxide by the microreactors made of tubular catalytic nanomembranes has recently attracted considerable attention. Catalytic microtubes play simultaneous roles of the oxygen bubble producing microreactors and oxygen bubble-driven micropumps. An autonomous pumping of peroxide fuel takes place through the microtubes by the recoiling microbubbles. Due to optimal reaction–diffusion processes, gas supersaturation, leading to favorable bubble nucleation conditions, strain-engineered catalytic microtubes with longer length produce oxygen microbubbles at concentrations of hydrogen peroxide in approximately ×1000 lower in comparison to shorter tubes. Dynamic regimes of tubular nanomembrane-based oxygen microbubble generators reveal that this depends on microtubes’ aspect ratio, hydrogen peroxide fuel concentration and fuel compositions. Different dynamic regimes exist, which produce specific bubble frequencies, bubble size and various amounts of oxygen. In this study, the rolled-up Ti/Cr/Pd microtubes integrated on silicon substrate are used to study oxygen evolution in different concentrations of hydrogen peroxide and surfactants. Addition of Sodium dodecyl sulfate (SDS) surfactants leads to a decrease of bubble diameter and an increase of frequencies of bubble recoil. Moreover, an increase of temperature (from 10 to 35 °C) leads to higher frequencies of oxygen bubbles and larger total volumes of produced oxygen.
Highlights
Oxygen gas has broad applications in clean energy, medicine, chemistry, biology
This study offers a better understanding of how different parameters of catalytic tubular microreactors and composition of hydrogen peroxide chemical fuel influence oxygen bubbles frequencies, radius and total volume, which pave the way towards a practical portable oxygen generator
Our definition of the nanomembrane does not exclude the existence of nanopores, due to multiple rotations of rolled-up layers, we assume that fabricated microtubes do not contain nanopores
Summary
Oxygen gas has broad applications in clean energy, medicine, chemistry, biology Conventional methods such as pressurized oxygen tanks, oxygen concentrators (i.e., separation from the air) and obtaining gas during water splitting suffer from high complexity and costs [1]. It was reported that higher concentrations of hydrogen peroxide and longer tubular lengths lead to higher frequencies of oxygen bubble recoil, a smaller total amount of oxygen is produced [29]. Oxygen evolution is studied using Ti/Cr/Pd catalytic microtubes by varying microtube length, SDS surfactant, solution surface tension, and concentration of H2O2 as parameters influencing frequencies of oxygen bubbles and total amounts of produced gas. This study offers a better understanding of how different parameters of catalytic tubular microreactors and composition of hydrogen peroxide chemical fuel influence oxygen bubbles frequencies, radius and total volume, which pave the way towards a practical portable oxygen generator
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