Hydrogen is the simplest molecule and the clearest balance sheet
Water electrolysis avoids carbon in the reactor and exposes the main economic terms: electricity price, conversion efficiency, utilization, stack replacement, balance-of-plant, compression, and delivered demand. CO₂ conversion, ammonia, methanol, and specialty chemicals inherit those terms and add competing reactions and more difficult separations.
Three numbers that locate the frontier
Hydrogen production includes many uses and routes. The energy floor is thermodynamic, not a plant quote; announced electrolysis capacity and laboratory selectivity are not operating output.
Cost per molecule is voltage and capital divided by useful product
The curve improves when more charge forms the desired molecule at lower voltage, higher current density, greater concentration, and longer component life—while the plant operates enough hours to repay itself.
Cheap intermittent power can raise delivered cost when stacks and downstream units sit idle or require buffers.
Hydrogen isolates efficiency and utilization; carbon and nitrogen products add selectivity, recycle, purification, and feed-origin accounting.
The headline metric sits on a system
Each layer can become the bottleneck even when the layer before it improves.
Feed and electricity
Water, nitrogen, CO₂, salts, or intermediates must arrive at controlled purity, pressure, carbon intensity, and price.
- Measure
- $/MWh · purity · pressure
- Failure mode
- Clean power and contaminants
Cell and stack
Catalysts, electrodes, membranes, electrolyte, flow fields, cooling, compression, and rectification convert charge into bonds.
- Measure
- V · A/cm² · stack life
- Failure mode
- Overpotential and degradation
Selectivity and separation
Faradaic yield, concentration, recycle, drying, and purification determine saleable output.
- Measure
- Faradaic efficiency · product wt%
- Failure mode
- Dilute and mixed streams
Storage, logistics, and demand
The molecule must be buffered, transported or used onsite, certified, and sold under contracts that support plant finance.
- Measure
- Delivered $/kg · firm offtake
- Failure mode
- Infrastructure and premium
Charge is conserved and conversion losses compound
Faraday's law fixes electrons per mole; thermodynamics fixes a minimum potential. Real plants add activation, resistance, mass transfer, pumping, drying, compression, and separation. Converting the product back to power compounds the penalty.
Cheaper reactors move scarcity into utilization and markets
Once a catalyst works, bankability depends on thousands of hours, replaceable stacks, impurity tolerance, concentrated output, shared infrastructure, credible carbon accounting, and buyers willing to contract above incumbent fossil cost.
Start with existing demand
Replace fossil hydrogen and reagents in ammonia, refining, and established chemical chains.
Raise useful current
Improve voltage, current density, selectivity, concentration, and component life together.
Integrate the plant
Use heat, recycle, storage, and flexible operation without starving continuous downstream units.
Contract the premium
Standards, procurement, quotas, and carbon policy convert environmental value into revenue.
An optimistic view, with conditions
Electrons become ordinary chemical feedstock
Electrochemistry wins first where the incumbent is carbon-intensive, clean electricity is structurally cheap, existing demand is concentrated, and cells produce a durable, concentrated stream that fits a repeatable plant.
Sources, method, and boundaries
IEA figures describe measured hydrogen production and project status. Faraday's law and heating value establish physical frames. Laboratory cell metrics are treated as component evidence, never as delivered plant cost.
