In Situ Measurement of Local Hydrogen Production Rate by Bubble-Evolved Recording

Xiaowei Hu,Liejin Guo,Yechun Wang

doi:10.1155/2013/568206

Xiaowei Hu, Liejin Guo + Show 1 more

Open Access

https://doi.org/10.1155/2013/568206

Copy DOI

Abstract

Hydrogen visibly bubbles during photocatalytic water splitting under illumination with above-bandgap radiation, which provides a direct measurement of local gas-evolving reaction rate. In this paper, optical microscopy of superfield depth was used for recording the hydrogen bubble growth on Cd0.5Zn0.5S photocatalyst in reaction liquid and illuminated with purple light. By analyzing change of hydrogen bubble size as a function of time, we understood that hydrogen bubble growth experienced two periods, which were inertia effect dominated period and diffusion effect dominated period, respectively. The tendency of hydrogen bubble growth was similar to that of the gas bubble in boiling, while the difference in bubble diameter and growth time magnitude was great. Meanwhile, we obtained the local hydrogen production rate on photocatalyst active site by measuring hydrogen bubble growth variation characteristics. This method makes it possible to confirm local actual hydrogen evolution rate quantitatively during photocatalytic water splitting.

Highlights

Hydrogen production from solar energy by splitting water directly using semiconductor material is a promising source of carbon-free energy [1]
Driven by the hydrogen molecules transfer due to supersaturation degree, hydrogen bubble will grow to a maxim size and detach from the catalyst surface into the reaction liquid
Interface between catalyst and reaction liquid lowers the free energy for bubble nucleation, which is a typical heterogeneous bubble nucleation process

Summary

Introduction

Hydrogen production from solar energy by splitting water directly using semiconductor material is a promising source of carbon-free energy [1]. For the heterogeneous photocatalytic reaction system, many issues concerning the semiconductor-liquid interface remain unsolved, such as the nature of the active sites and confirmation for actual reaction rate and hydrogen evolution rate [8, 9]. Driven by the hydrogen molecules transfer due to supersaturation degree, hydrogen bubble will grow to a maxim size and detach from the catalyst surface into the reaction liquid. The investigations on hydrogen bubble evolution characteristics will help understanding the hydrogen transfer process and the effects of the solid-liquid interface and heterogeneous system, but the research on this field is almost blank. Of the local active sites or the structuring surface providing only the average reaction rate. The hydrogen production rate on local active sites will be obtained and analyzed

Experimental Section

Results and Discussion

Conclusions