CO₂ reduction to valuable products is a centerpiece of future energy and sustainability technologies, yet progress in developing efficient and selective catalysts has been limited by the challenges in measuring the performance of electrocatalysts, including sensitivity to the electrochemical environment and the breadth of possible reaction products. The ideal characterization of a given catalyst is quantitative measurement of the activity and product distribution, as a function of time and for a large range of overpotentials since product distributions vary with aging of the operational catalyst as well as the operating potential. This combination of desired measurement attributes is incompatible with traditional experiments, perhaps most notably due to the duration of quantitative product distribution measurements, which impedes measurements over a range of overpotentials and severely limits the measurement frequency to observe variations in product distribution. We present principled design of high throughput screening systems and discuss the implications that these designs have for large-scale reactors. We will also discuss initial results of the high throughput screening that reveal surprising compositional trends in product distributions and provide key examples of where understanding of the uniqueness of Cu in producing high-order products needs to be further developed.