Systematic study of the influence of iR compensation on water electrolysis

Water electrolysis has been one of the most studied topics in materials research in the past decade because of the global effort in exploring clean and renewable energy sources. Much effort has been devoted to developing highly active electrocatalysts for the two half reactions of water electrolysis, the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Some reported electrocatalysts are even superior to the benchmark platinum and iridium dioxide catalysts, and thus are claimed to be promising for large-scale commercial use. However, most electrochemical data in the literature are reported after iR compensation, where R is the overall resistance, including contact resistance, charge-transfer resistance, and intrinsic resistance. Unfortunately, these types of resistance cannot be avoided in real electrolyzers, which means that R still results in energy consumption if the electrocatalysts are used for industrial water electrolysis. Thus, the data with iR compensation are always misleading, and setting criteria for iR compensation in analyses of water electrolysis is urgently needed to instruct the scientific community. In this work, we test the catalytic performance of several reported HER and OER catalysts with and without iR compensation and discuss the contribution from iR compensation under small and large current densities. We also present a comparative study between two iR compensation methods (automatic and manual iR compensation). Finally, we propose some strategies to reduce the R to achieve better performance without iR compensation, which is necessary for industrial applications.