Artificial Photosynthesis: Turning Sunlight, Water and CO2 into Fuel

Artificial photosynthesis replaces a leaf's biological machinery with engineered semiconductor photoelectrodes and catalysts. Sunlight drives two linked half-reactions inside a photoelectrochemical cell: water is oxidized into oxygen, protons and electrons on one side, while those electrons and protons reduce captured CO₂ into a usable fuel — methanol, syngas or other hydrocarbons — on the other. This simulator models a working cell so you can see how sunlight intensity, photoelectrode capture efficiency, electrolyzer efficiency and catalyst choice change the solar-to-fuel efficiency, the daily fuel output and how much CO₂ the plant actually processes.

Sunlight & Capture

Sunlight intensity 800 W/m²

Photoelectrode capture η 21%

Electrolysis

Electrolyzer efficiency 74%

Catalyst

Solar-to-fuel efficiency

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Fuel output

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CO2 processed

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How it works

Every stage of the cell loses some of the sunlight's energy before it reaches the fuel molecule. Chaining the three efficiencies together gives the overall solar-to-fuel figure that governs how much fuel a fixed panel area can make in a day.

η_total = η_capture x η_electrolyzer x η_selectivity
P_chem (kW) = I x A x η_total / 1000
fuel (kg/day) = P_chem x 86.4 / E_fuel
CO2 (t/day)  = fuel x r_CO2 / 1000

I — sunlight intensity in W/m²; A — fixed 500 m² panel array.
η_capture — photoelectrode solar-capture efficiency; η_electrolyzer — how much of the captured electrical energy the water-splitting/CO₂-reduction cell actually delivers.
η_selectivity — the fraction of reduction current that lands on the target product: copper's multi-carbon pathway (methanol, E_fuel = 22.7 MJ/kg, r_CO2 = 1.37) is less selective than cobalt oxide's cleaner syngas route (E_fuel = 12 MJ/kg, r_CO2 = 0.85).
86.4 — seconds-to-day conversion in MJ units (kW x 86,400 s / 1,000).

Bars are normalised against a realistic ceiling for each metric, so they saturate at the top of the display rather than running off-scale at extreme settings.

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Why the numbers compound down

Real plants convert well under 1% of incoming sunlight into stored chemical energy; the best engineered photoelectrochemical systems have reported laboratory efficiencies above 15-19% for hydrogen. But once you chain solar capture with electrolyzer losses and then with the selectivity of the CO₂-reduction catalyst, the realistic system-level number for a liquid fuel is much lower — which is exactly what the three sliders and the catalyst toggle above let you explore.