Physics

Photocathode

Electron

Nanotechnology

Electrode

Organic chemistry

Hydrogen

Photocatalysis

Heterojunction

Engineering

Faraday efficiency

Catalysis

Physical chemistry

Chemistry

Metallurgy

Materials science

Ethylene

Degradation (telecommunications)

Photocurrent

Oxide

Computer science

Quantum mechanics

Electrolyte

Chemical engineering

Optoelectronics

Biochemistry

Redox

Photochemistry

Telecommunications

Artificial photosynthesis

Nature Energy

The chemical transformations that occur in metal oxides under operating conditions limit their applications for artificial photosynthesis. Understanding these chemical changes is a prerequisite to achieve sustainable production of solar fuels and chemicals. Herein, we use a correlative approach to unravel how cuprous oxide (Cu2O) photoelectrodes change under reaction conditions and, consequently, provide a protection scheme to mitigate degradation. In agreement with theoretical predictions, we find that under illumination the Cu2O concurrently undergoes reduction by photoelectrons and oxidation by holes in the material at electrolyte-dependent degradation rates. These mechanistic insights led us to design a protection scheme that uses a silver catalyst to accelerate transfer of photogenerated electrons and a Z-scheme heterojunction to extract holes. The resulting photocathode exhibits a stable photocurrent for CO2 reduction with ~60% Faradaic efficiency for ethylene with a balance of hydrogen for hours, whereas bare Cu2O degrades within minutes. Photoelectrodes for light-driven CO2 reduction to fuels and chemicals often suffer drastic decreases in performance due to changes in the material under illumination. Here the authors investigate the degradation pathways that occur in Cu2O photocathodes for ethylene synthesis and put forward strategies to mitigate them.

Investigation and mitigation of degradation mechanisms in Cu2O photoelectrodes for CO2 reduction to ethylene