Recommended Practices and Benchmark Activity for Hydrogen and Oxygen Electrocatalysis in Water Splitting and Fuel Cells

Abstract

Electrochemical energy storage by making H2 an energy carrier from water splitting relies on four elementary reactions, i.e., the hydrogen evolution reaction (HER), hydrogen oxidation reaction (HOR), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). Herein, the central objective is to recommend systematic protocols for activity measurements of these four reactions and benchmark activities for comparison, which is critical to facilitate the research and development of catalysts with high activity and stability. Details for the electrochemical cell setup, measurements, and data analysis used to quantify the kinetics of the HER, HOR, OER, and ORR in acidic and basic solutions are provided, and examples of state‐of‐the‐art specific and mass activity of catalysts to date are given. First, the experimental setup is discussed to provide common guidelines for these reactions, including the cell design, reference electrode selection, counter electrode concerns, and working electrode preparation. Second, experimental protocols, including data collection and processing such as ohmic‐ and background‐correction and catalyst surface area estimation, and practice for testing and comparing different classes of catalysts are recommended. Lastly, the specific and mass activity activities of some state‐of‐the‐art catalysts are benchmarked to facilitate the comparison of catalyst activity for these four reactions across different laboratories.

3D Carbon Materials for Efficient Oxygen and Hydrogen Electrocatalysis

“…Water electrolysis via the HER can generate clean and pure hydrogen that can then be employed in PEM fuel cells . Due to the relatively simple mechanism, hydrogen electrocatalysis kinetics are generally more facile than for oxygen electrocatalysis, making it possible to achieve very high exchange current density at negligible voltage loss even with minimal catalyst loading . However, Pt‐based electrocatalysts are still the most active compounds for HER catalysis .…”

Ultrafine Defective RuO2 Electrocatayst Integrated on Carbon Cloth for Robust Water Oxidation in Acidic Media

“…In principle, unpaired electrons can be trapped by oxygen vacancy. In order to minimize the effect of capacitive current, the polarization curves were derived by taking average of the positive-going and negative-going scans of measured cyclic voltammogram (CV), [50] and then iR-correction was performed ( Figure S9, Supporting Information). As a result, the newly emerged peak, which has a higher binding energy than lattice oxygen, may be attributed to oxygen atoms adjacent to defects.…”

Antiferromagnetic Inverse Spinel Oxide LiCoVO4 with Spin‐Polarized Channels for Water Oxidation

“…CV potential range was from 0.9 to 1.6 V (vs reversible hydrogen electrode (RHE)) with a scan rate of 10 mV s −1 . The OER current densities are normalized by Brunauer–Emmett–Teller (BET) surface area to present the intrinsic catalytic activity . And the iR correction was applied to calibrate the working potential.…”