The ability to follow charge and spin dynamics at surfaces is necessary to understand the material properties, which mediate carrier lifetime and determine energy conversion efficiency. To realize this goal, we have constructed an ultrafast tabletop extreme ultraviolet (XUV) light source. Reflection–absorption (RA) spectroscopy using this light source combines the benefits of x-ray absorption, such as element, oxidation, and spin state specificity, with surface sensitivity and ultrafast time resolution, having a probe depth of less than 3 nm and a time resolution faster than 100 fs. This technique is applied to the study of electron trapping and defect-mediated recombination at the surface of NiO. Direct observation of ultrafast electron trapping and subsequent recombination shows that grain boundaries rather than oxygen vacancies are primarily responsible for fast electron-hole pair recombination. This result clarifies the design parameters for NiO water oxidation catalysts by showing that oxygen vacancies, which enhance catalytic activity, have no detrimental effect on carrier lifetime. Rather, carrier lifetime can be dramatically extended by the elimination of near-surface grain boundaries even in the presence of chemically active oxygen vacancies. Finally, we explore several examples where ultrafast spin crossover in semiconductor photocatalysts may play an important role in the material’s photochemical performance.