# Decoupling Adsorption and Photocatalysis: Addressing the Dark Adsorption Pitfall in Catalyst Ranking

## TL;DR

This paper addresses how adsorption effects can mislead rankings of photocatalysts and proposes a method to minimize these effects.

## Contribution

A new low-concentration method is introduced to decouple adsorption and photocatalysis effects in catalyst evaluation.

## Key findings

- Adsorption rates and capacities vary significantly among similar photocatalysts like ZnO-based materials.
- Using a low-concentration approach changes catalyst rankings by minimizing dark adsorption effects.
- Standard evaluation methods often fail to account for adsorption differences, leading to misleading results.

## Abstract

Heterogeneous photocatalysis relies on the adsorption
of the target
molecule to the surface of the catalyst and the photocatalytic action
of the material to degrade target molecules. In many reports, a 30
min dark adsorption time is used prior to exposure of the system to
light and initiation of photocatalysis with no discussion of differences
in adsorption rate or capacity when comparing catalystswhen
adsorption rates or capacities are very different, misleading catalyst
rankings may result. Even closely related materials, such as the ZnO-based
photocatalysts discussed here, adsorb target molecules at different
rates, have different adsorption capacities, and have apparently different
photocatalytic rates. When typical methods for evaluating photocatalysts
are used, the adsorption effects are not accounted for. Here, we illustrate
potential concerns while evaluating photocatalysts and present a simple,
low-concentration method to possibly addressand avoidadsorption
effects. Interestingly, catalyst rankings change when adsorption effects
are minimized by circumventing dark adsorption using the low concentration
approach presented.