(690c) Experimental Methods to Benchmark Electrocatalysts for Hydrogen Evolution and Oxygen Evolution

Objective evaluation of electrocatalytic activity for oxygen evolving and hydrogen evolving catalysts is of fundamental importance for the development of solar water-splitting devices.  However, current testing methods employed in catalysis research are far from standardized, making it difficult to cross-compare the activity and stability of these systems.  Even the definition of activity can vary significantly from study to study; for instance, when comparing catalytic activity some authors choose to report the exchange current density while others choose to report either the overpotential required to achieve a fixed current density or the measured current density at a fixed operating potential.  Moreover, current density itself can be defined either per geometric area, BET-active surface area, electrochemically active surface area, and so on.  These differences in testing protocols and reporting results can complicate comparisons of catalyst activity.  In this tutorial session, an overview of the standard methods used within the Benchmarking facility of the Joint Center for Artificial Photosynthesis (JCAP) will be discussed.  In particular, the presentation will focus on standard techniques used for determining electrochemically-active surface areas, measuring electrocatalytic activity and stability, and analyzing electrocatalytic products.  The tutorial will also highlight some of the challenges and limitations regarding these measurements.  Figures of merit for electrocatalytic hydrogen evolving and oxygen evolving reactions and ways of presenting relevant data to broad scientific audiences will also be discussed.