Theory

Theory#

Electrochemical stability window#

These are the most important reactions that occur on any electrode in aqeous electrolyte.

The potentials given are the standard redox potentials for the conversion between H2/O2 <-> H2O. Platinum is a really good catalyst for HER/HOR so the onset for both reactions is respectively <0V and >0V but OER/ORR start at a significant overpotential of at least 0.2 V for the best catalysts.

1) Hydrogen evolution reaction (HER) @ <0 V vs. RHE

Acidic:

\[\mathrm{2 H^+ + 2e^-\rightarrow H_2}\]

Alkaline:

\[\mathrm{2 H_2O + 2e^-\rightarrow H_2 + 2 OH^-}\]

2) Hydrogen oxidation reaction (HOR) @ >0 V vs. RHE

What are the reactions for acidic and alkaline conditions?

3) Oxygen evolution reaction (OER) @ >>1.23 V vs. RHE

Acidic:

\[\mathrm{2 H_2O\rightarrow O_2 + 4 H^+ + 4 e^-}\]

Alkaline

Hint, it involves \(\mathrm{OH^-}\)

Tutorial paper about cyclic voltammetry and electrochemistry

  • A Practical Beginner’s Guide to Cyclic Voltammetry [10]

  • Electrochemistry for the Non-Electrochemist [11]

Reference about pH effect Mechanistic understanding of pH effects on the oxygen evolution reaction [12]

Basic idea of catalyst preparations Oxidatively Electrodeposited Thin-Film Transition Metal (Oxy)hydroxides as Oxygen Evolution Catalysts [13]

References about oxygen evolution reaction

  1. Oxygen Evolution Reaction Electrocatalysis on Transition Metal Oxides and (Oxy)hydroxides: Activity Trends and Design Principles [14]

  2. Nickel–iron oxyhydroxide oxygen-evolution electrocatalysts: the role of intentional and incidental iron incorporation [15]

  3. Research progress on high entropy alloys and high entropy derivatives as OER catalysts [16]

  4. Manganese oxide with different composition and morphology as electrocatalyst for oxygen evolution reaction [17]

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