Physical Transformation AtlasPTA
Constraint · constraint:gibbs-enthalpy-ratio-bound

Reversible electrochemical efficiency (ΔG/ΔH)

An electrochemical converter operating reversibly delivers the Gibbs free-energy change of its reaction as electrical work, so its efficiency on the reaction enthalpy cannot exceed ΔG/ΔH — 83 % for hydrogen and oxygen at standard conditions with liquid water as the product. A ratio of the reaction's own thermochemistry, not of temperatures: for the direct oxidation of carbon ΔG exceeds ΔH and the ratio passes 100 %. Evaluated only against an efficiency datum that records both ΔG and ΔH of its reaction on the same basis.

Atlas record: 1 claim references this constraint — 1 established.

Explorerelations · sources · cite

η ≤ ΔG/ΔH of the cell reaction; 237.1/285.8 = 0.83 for H₂ + ½O₂ → H₂O(l) at 25 °C, 1 atm (higher-heating-value basis)

1claims0enumerated routes0routes with complete-composition evidence0candidate routes not searched2cited sources

Relations

bounded by · 1
Fuel-cell electro-oxidation—bounded by→Reversible electrochemical efficiency (ΔG/ΔH)established
  • efficiency on the reaction enthalpy (higher-heating-value basis for hydrogen with liquid water as product)

Cited sources · 2

  1. [1]
    EG&G Technical Services, Inc.. Fuel Cell Handbook (Seventh Edition) (2004)
    U.S. Department of Energy, Office of Fossil Energy, National Energy Technology Laboratory, under contract DE-AM26-99FT40575, November 2004 · www.netl.doe.gov/sites/default/files/netl-file/FCHandbook7.pdf · record
  2. [2]
    A. J. Bard, L. R. Faulkner. Electrochemical Methods: Fundamentals and Applications (2nd ed.) (2001)
    Wiley · book, no DOI · record

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Physical Transformation Atlas (2026). entity constraint:gibbs-enthalpy-ratio-bound: Reversible electrochemical efficiency (ΔG/ΔH). Dataset revision rbfbfcbb70e57 (hash of the canonical data). https://physical-transformation-atlas.wldud5192.workers.dev/e/constraint/gibbs-enthalpy-ratio-bound

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