Abstract
This short essay urges the community of those who study electrocatalysis and photocatalysis to report measures of the number of active sites in heterogeneous catalysts (especially the redox sites in an electrocatalyst) and the number of photons involved in photoconversions. An example of the former is the use of CO stripping for catalysts containing platinum-group metals and N(2)O titration to count redox sites in supported electrocatalysts containing base metals that do not strongly chemisorb CO or hydrogen. A minimal example of the latter is to report energy density as a way to bridge between batch photolysis and flow photoinitiated reactions.