Hydrogen Evolution Reaction (HER)¶

The Hydrogen Evolution Reaction is the cathodic reaction in water electrolysis for green hydrogen production.

Reaction¶

\[2H^+ + 2e^- \rightarrow H_2\]

In alkaline conditions:

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

Key Descriptor¶

The activity descriptor is the hydrogen adsorption energy ($\Delta E_H$):

\[\Delta E_H = E_{surface+H} - E_{surface} - \frac{1}{2}E_{H_2}\]

Sabatier Optimum¶

Based on the pioneering work of Nørskov and coworkers:

Optimal Binding

$\Delta E_{opt} = -0.27$ eV

Catalysts at this energy show thermoneutral hydrogen binding - the ideal balance between H⁺ adsorption and H₂ desorption.

Configuration¶

from ascicat.config import HER_CONFIG

print(f"Optimal energy: {HER_CONFIG.optimal_energy} eV")
print(f"Activity width: {HER_CONFIG.activity_width} eV")
print(f"Activity window: {HER_CONFIG.activity_window} eV")

Full Configuration¶

Parameter	Value	Description
`optimal_energy`	-0.27 eV	Sabatier peak
`activity_width`	0.15 eV	Scoring tolerance
`activity_window`	[-0.60, +0.10] eV	Analysis range
`stability_range`	[0.1, 5.0] J/m²	Surface energy range
`cost_range`	[$1, $200,000]	Material cost range

Usage Example¶

from ascicat import ASCICalculator

# Initialize for HER
calc = ASCICalculator(reaction='HER', verbose=True)

# Load HER data
calc.load_data('data/HER_clean.csv')

# Calculate with equal weights
results = calc.calculate_asci(w_a=0.33, w_s=0.33, w_c=0.34)

# Top catalysts
top = calc.get_top_catalysts(n=10)
print(top[['symbol', 'ASCI', 'DFT_ads_E']])

Benchmark Materials¶

Known HER catalysts and their binding energies:

Material	$\Delta E_H$ (eV)	Activity	Cost
Pt(111)	-0.09	Excellent	Very High
Ni(111)	-0.47	Moderate	Low
Co(111)	-0.35	Good	Low
Au(111)	+0.18	Poor	High
Fe(110)	-0.40	Moderate	Very Low
MoS₂	-0.08	Good	Low

The HER Volcano¶

Exchange
Current
   ↑
   |        Pt★
   |       /  \
   |    Pd/    \Ir
   |   Rh/      \
   |   /         \Au  Ag
   | Ni  Mo  W    \
   |/              \
   |________________\_____→ ΔE_H (eV)
  strong          weak
  binding        binding

Screening Strategy¶

For HER catalyst discovery:

Equal weights for initial exploration
Focus on catalysts with $|\Delta E_H - (-0.27)| < 0.15$ eV
Prioritize stability for industrial applications
Consider cost for large-scale deployment

Weight Recommendations¶

Application	$(w_a, w_s, w_c)$	Rationale
Fundamental research	(0.5, 0.3, 0.2)	Focus on mechanism
Lab-scale electrolyzer	(0.4, 0.4, 0.2)	Balance performance/durability
Commercial electrolyzer	(0.35, 0.40, 0.25)	Emphasize durability
Large-scale deployment	(0.35, 0.30, 0.35)	Consider economics

Scientific References¶

Nørskov, J. K. et al. J. Electrochem. Soc. 152, J23 (2005)
Greeley, J. et al. Nat. Mater. 5, 909 (2006)
Seh, Z. W. et al. Science 355, eaad4998 (2017)