Photochemical processes are fundamental to the function of advanced devices and materials such as solar cells and photocatalysts. The mechanisms of these processes are typically inferred through a combination of ab initio quantum calculations and various spectroscopic methods, some of which provide detailed time resolution, allowing for the deduction of important transient species. Single crystal X-ray diffraction experiments generally produce structures that are time-averaged over several hours, thus lacking information about the dynamics of all but the slowest systems. In this work, we combined the strengths of spectroscopic and diffraction methods to provide rich structural information with fine time resolution. This time resolution was achieved using the Timepix3-based event-counting TRISTAN detector, developed at Diamond Light Source, which also enabled flexible post-experiment reprocessing and allowed for real-time data collection strategy decisions. Utilizing this detector technology in a laser-pump/X-ray probe experiment, we identified a transient charge-separated species implicated in a photocatalytic water splitting reaction.