Researchers Demonstrate Wavelength-Dependent Control of CO2 Reduction Selectivity Using Plasmonic Catalysts
Researchers used operando scanning photoelectrochemical microscopy (photo-SECM) on plasmonic Au/p-GaN photocathodes to demonstrate that photon energy directly controls which products form during CO2 reduction — CO under visible interband excitation (460–560 nm) or hydrogen under near-infrared intraband excitation (640–800 nm). The team also found that nanostructure geometry gates selectivity, with sub-100 nm structures sustaining CO2 reduction activity while ~300 nm nanodisks lose it due to hot-carrier transport losses. These findings resolve a longstanding debate about the origin of plasmon-driven selectivity and establish a framework for designing light-driven catalysts for fuel and chemical synthesis.
A study posted to arXiv presents quantitative operando photo-SECM measurements on Au/p-GaN plasmonic photocathodes, directly linking photon energy to CO2 reduction (CO2R) product selectivity. Interband excitation at 460–560 nm selectively drives CO production, while intraband excitation at 640–800 nm favors hydrogen evolution, with constant absorbed power maintained across wavelengths to isolate electronic hot-carrier effects from photothermal or photonic artifacts. Density functional theory (DFT) calculations corroborate the experimental results, showing that higher-energy interband excitation increases the overlap between hot-electron-accessible states and the CO-producing reaction intermediate, preferentially promoting CO over formate. The study further demonstrates a geometric gating effect: sub-100 nm nanostructures sustain CO2R activity, whereas ~300 nm nanodisks suffer hot-carrier transport losses that suppress it, consistent with ab initio transport modeling. Together, the results identify photon energy, hot-carrier transport, and nanostructure geometry as three coupled and tunable design parameters for plasmonic CO2R. The authors argue that these findings settle a longstanding debate on whether plasmon-driven selectivity arises from electronic, thermal, or photonic mechanisms, attributing it primarily to hot-carrier energy. The work also positions photo-SECM as a broadly applicable platform for studying photo(electro)catalytic systems under realistic operating conditions.
What's missing
The study is a preprint and has not yet undergone peer review. Key open questions include whether the observed selectivity trends generalize beyond Au/p-GaN to other plasmonic material systems, how catalyst stability and durability perform over extended operation, and whether the photo-SECM methodology scales to more complex or industrially relevant electrode geometries.
What different sources said
- arXiv physicsCenter
Revealing Wavelength- and Size-Dependent CO2 Reduction Selectivity via Operando Scanning Photo-Electrochemical Microscopy
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