HIT: Au1/CeO2 single-atom photocatalyst converts CO2 to CH4 with 92% selectivity
Researchers at HIT anchored isolated Au atoms on CeO2 nanosheets; kinetic isotope data show CO2 hydrogenation to CH4 is not exclusively a PCET process.
A team at HIT has built an Au1/CeO2 photocatalyst by anchoring isolated gold single atoms onto CeO2 nanosheets. According to the authors, the material reversed the hydrogenation pathway and reached 92% selectivity for CH4 under CO2 and H2O atmospheres dx.doi.org
dx.doi.orgdx.doi.orgOpen source ↗. The experimental study appeared in Science China Chemistry (dx.doi.org, DOI 10.1007/s11426-026-3523-3) and was announced on 5 November 2026.
The work addresses a mechanistic question that had remained open, namely which hydrogenation route governs selectivity in photocatalytic CO2 reduction.
Why CH4 selectivity is hard to achieve
The conversion of CO2 to CH4 involves the transfer of eight electrons and eight protons, and therefore typically shows low selectivity dx.doi.org
dx.doi.orgdx.doi.orgOpen source ↗. In earlier studies, photocatalytic reduction of CO2 to CH4 was generally considered to follow the Eley–Rideal (E-R) mechanism, which proceeds through proton-coupled electron transfer (PCET). The authors note that CO2 hydrogenation may also involve a Langmuir–Hinshelwood (L-H) mechanism mediated by surface-adsorbed *H species. Which of the two actually controls selectivity was unclear.
Two mechanisms on one catalyst
Kinetic isotope effect (KIE) results indicated that the two hydrogenation steps on Au1/CeO2 follow different mechanisms. The conversion of CO2 to *CO follows the E-R mechanism, while the conversion of *CO to CH4 follows the L-H mechanism dx.doi.org
dx.doi.orgdx.doi.orgOpen source ↗. This is why the title states that the pathways are not exclusively PCET processes.
The authors attribute the result to a lower Gibbs free energy (∆G) for *CO hydrogenation and to regulated hydrolysis behavior. Together these make Au1/CeO2 more favorable for *CO hydrogenation when the *H supply is sufficient.
In situ mass spectrometry, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT) calculations were combined in the study. They further showed that a balanced *H supply plays a critical role in selective CH4 generation over Au1/CeO2 dx.doi.org
dx.doi.orgdx.doi.orgOpen source ↗. The authors say the work offers a new understanding of the hydrogenation pathway in CH4 photosynthesis.
