Field Heterogeneities and Their Impact on Photocatalysis: Combining Optical and Kinetic Monte Carlo Simulations on the Nanoscale

Abstract

Gaining insights into the working principles of photocatalysts on an atomic scale is a challenging task. The obviously high complexity of the reaction mechanism involving photoexcited electrons and holes is one reason. Another complicating aspect is that the electromagnetic field, driving photocatalysis, is not homogeneous on a nanoscale level for particle-based catalysts as it is influenced by the particle's shape and size. We present a simple model, inspired by the CO 2 reduction on titania anatase, which addresses the impact of these heterogeneities on the photocatalytic kinetics by combining kinetic Monte Carlo with electromagnetic wave simulations. We find that average activity and especially efficiency might differ significantly between different particles. Moreover, we find sizable variation of the catalytic activity on a single facet of a nanocrystal. Besides this quantitative heterogeneity, the coverage situation in general changes laterally on this facet, and we observe a concomitant change of the ratedetermining steps. This heterogeneity on all levels of photocatalytic activity is masked in experimental studies, where only the spatially averaged activity can be addressed. Microkinetic models based on experimental findings might therefore not represent the true microscopic behavior, and mechanistic conclusion drawn from these needs to be handled with care.

Kinetic Monte Carlo simulations for heterogeneous catalysis: Fundamentals, current status, and challenges

“…This impetus is expected to spread to other branches of heterogeneous catalysis not covered in this article, like for instance electrocatalysis, [303][304][305][306][307][308] and photocatalysis. [309][310][311] The KMC approach will thus (continue to) drive exciting breakthroughs in the quest towards understanding and predicting catalytic materials for niche applications. 1 -w a y s k i p l i s t 2 -w a y s k i p l i s t…”

Establishing the Role of Operating Potential and Mass Transfer in Multicarbon Product Generation for Photoelectrochemical CO2 Reduction Cells Using a Cu Catalyst

“…Previous PEC CO 2 R modeling efforts have explored device architectures, , reaction mechanisms, − and multiscale modeling approaches. , In this report, we build upon the prior computational work by presenting a model for simulating the performance of PEC CO 2 R, which accounts for photoabsorber performance, catalyst kinetics, and mass transport through the boundary layer. This model is then used to define the operating conditions and design considerations required for optimal solar-to-C 2+ (STC 2+ ) rates as well as to reveal how the PEC device performs with a changing microenvironment (i.e., the electrolyte environment directly adjacent to the catalyst surface).…”

Emerging Strategies for CO2 Photoreduction to CH4: From Experimental to Data‐Driven Design

“…A kinetic model is still needed to understand the photocatalytic CO 2 RR process. Hammerschmidt et al [207] used kinetic Monte Carlo combined with electromagnetic wave simulations to address the effect of inhomogeneous light absorption on the photocatalytic activity of semiconductor particles, but the model lacks consideration of charge carrier transport and intermediate reaction products. DFT calculations can solve the above problems, but DFT calculation combined with the kinetic model to study the photocatalytic CO 2 RR process is hindered by computational cost.…”