Nanodiamond Spin Probes for Sensing Reactive Intermediates in Heterogeneous Photocatalysis

Heterogeneous photocatalysts are promising materials for turning solar energy into chemical fuels, but their widespread application is hampered by low efficiency and selectivity. To facilitate future catalyst design, the evaluation of reactive intermediates, such as reactive oxygen species (ROS), formed during photocatalysis is vital. Challenges arise in ROS detection due to their high reactivity and interactions with the catalyst surface. Techniques such as electron paramagnetic resonance (EPR) often rely on bulk‐sensing apparatus that are highly sensitive but have poor spatial resolution. Here, a fast in situ method for evaluating the performance of photocatalysts in ROS formation is developed, utilizing nitrogen‐vacancy (NV) centers in fluorescent nanodiamond (FND) particles as sensors. This work demonstrates the ability to detect ROS (e.g., • OH, O 2 •– ) in both the absence and presence of spin‐trap adducts (e.g., 5,5‐Dimethyl‐1‐pyrroline N‐oxide, DMPO), the latter allowing for further ROS identification by EPR. An exploration of various photocatalysts demonstrates the technique's ability to probe ROS generation during photocatalysis. Correlation with bulk photocatalytic activity highlights the method's suitability for rapidly evaluating photocatalyst efficiency. This methodology shows promise for sensing local, nanoscale photocatalytic activity on catalyst surfaces and can act to expedite the discovery of next‐generation catalysts.