Recently, a collaborative research team led by the U.S. National Academy of Sciences, Engineering, and Medicine member and Rice University Professor Naomi J. Halas and Professor Peter Nordlander published their latest findings in the journal Nature Catalysis, titled “Steam methane reforming using a regenerable antenna–reactor plasmonic photocatalyst.”
The researchers combined a plasmonic Cu antenna with catalytically active Rh to form a Cu-Rh surface alloy. This AR photocatalyst provides an efficient and selective pathway for steam methane reforming (SMR). SMR via photocatalysis is primarily driven by plasmon-mediated hot carriers, which reduce the apparent energy barrier and enhance catalytic stability. Without hot carriers, thermal catalysis leads to catalyst deactivation due to oxidation and coking. The thermally deactivated catalyst can be regenerated under photocatalytic conditions, restoring reactivity and selectivity under illumination. The Cu₁₉.₅Rh₀.₅ photocatalyst exhibited the highest hydrogen turnover frequency (H₂ TOF) of 0.308 s⁻¹ and a space-time yield of 15.6 μmol·cm⁻³·s⁻¹, compared to the benchmark value of 1 μmol·cm⁻³·s⁻¹ in large-scale catalytic processes.
• Plasmonic photocatalysis approach: Utilized hot carriers generated by surface plasmon decay in metal nanoparticles to overcome limitations in previous SMR photocatalysis research.
• Hot-carrier-driven reaction mechanism: Found that SMR via photocatalysis is primarily driven by plasmon-mediated hot carriers, which reduce apparent energy barriers and improve catalytic stability.
• Catalyst regeneration capability: Thermally deactivated catalysts can be regenerated under resonant illumination, restoring reactivity and selectivity in photocatalytic conditions.
• Spectral dependency of photocatalytic reactions: Product formation was studied by varying excitation wavelengths, showing that reaction activity and selectivity are wavelength-dependent, enabling optical control of chemical selectivity.
Figure 1. Steam methane reforming (SMR) via photocatalysis
Figure 2. Mechanism study of SMR photocatalysis
Figure 3. Thermal deactivation and photocatalytic regeneration
Figure 4. Study on photocatalytic regeneration mechanism
In processes like methane reforming for hydrogen production and Fischer–Tropsch synthesis, reaction conditions significantly influence outcomes. Key factors include light intensity/area and reaction temperature/pressure, which affect the reaction nature and selectivity.
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Steam methane reforming (SMR) is the primary industrial process for hydrogen production globally, accounting for half of the world’s hydrogen output. Traditional thermal methods require high temperatures and are carbon-intensive. Photocatalytic SMR offers a pathway to lower activation energy and avoid high temperatures but is currently limited by ultraviolet light exposure or additional heating requirements. As mentioned earlier, optimizing Rh loading and wavelength dependence of its photo-reactivity, Cu-Rh AR photocatalysts exhibit reactivity, selectivity, and stability for SMR photocatalysis. Under thermal and dark conditions, photocatalysts deactivate rapidly but can be fully regenerated for SMR photocatalysis. Detailed elemental evolution during thermal deactivation and photocatalytic regeneration highlights hot-carrier-driven processes facilitating desorption of C and O intermediates and restoring catalysts to a lower oxidation state, ensuring reliable recovery of photocatalytic activity. The hot-carrier-driven desorption process is crucial for catalyst reactivation, extending its lifespan, and enabling widespread regeneration of deactivated catalysts.
Steam methane reforming using a regenerable antenna–reactor plasmonic photocatalyst, Yigao Yuan, Jingyi Zhou, Aaron Bayles, Hossein Robatjazi, Peter Nordlander* and Naomi J. Halas*, Nature Catalysis, 10.1038/s41929-024-01248-8.
