Reducing instability in dispersed powder photocatalysis derived from variable dispersion, metallic co-catalyst morphology, and light fluctuations

Abstract

The need for sustainable chemicals has increased the numbers of published studies about photocatalytic hydrogen production via photoreforming and water-splitting. However, comparison of results, already complicated by non-standardized reaction setups and instrumentation, can be further hampered by variation in degree of powdered catalyst dispersion and temporal instability related to co-catalyst morphology and the reaction setup. Building on guidelines already in the literature, we demonstrate the degree to which these sources of variation can impact apparent photocatalytic rates: in the worst cases, variable dispersion caused up to ~400% variation in activity for the same powdered photocatalyst, photodeposition of a Pt co-catalyst contributed to a lengthy activation period lasting up to two hours, and lamp instability increased quantum yield measurement error by a factor of four. To reduce impacts from these instabilities, we recommend mechanically and chemically tuning the particle sizes in dispersion to increase dispersion stability, avoiding comparisons across samples during the initial activation period, and ensuring lamp output stability on the timescale of the reaction. It is also informative to report particle size distributions, zeta potentials, and time-resolved catalytic activity.

Keywords

• Deactivation
• Dispersion
• Deposition
• Sonication
• Light intensity profile