Tailoring High‐Entropy Oxide via Grain Boundary Engineering to Establish Adjacent Asymmetric Redox Sites for Full‐Spectrum Photothermal Catalytic CO2 Reduction

Why It Matters

This microstructural strategy overcomes kinetic bottlenecks in CO2 photoreduction, offering a scalable pathway toward efficient carbon‑neutral catalytic processes.

Key Takeaways

• Grain boundaries generate asymmetric Fe‑Vo‑Cr‑O redox sites.
• Fe sites act as Lewis acids for water activation.
• Cr‑O clusters preferentially adsorb CO2 via bridging mode.
• Photothermal heating reaches ~198 °C, boosting reaction kinetics.
• CH4 and CO yields exceed 600 µmol g⁻¹ h⁻¹ each.

Pulse Analysis

Photothermal catalysis has emerged as a compelling route for converting CO2 into value‑added fuels, yet most catalysts struggle with mismatched rates of CO2 activation, proton generation, and electron transfer. High‑entropy oxides (HEOs) bring compositional complexity and tunable electronic structures, but their intrinsic activity is often limited by random defect distributions. By focusing on grain boundary density, researchers can deliberately reshape the local electronic landscape, turning what was previously a defect liability into a design asset.

In the reported (CoCrFeMnNi)3O4 nanosheets, dense grain boundaries induce asymmetric oxygen vacancies that link Fe and Cr cations. The Fe‑Vo‑Cr‑O motifs act as dual‑function sites: Fe centers, rendered electron‑deficient, serve as Lewis acids that split water to supply protons, while neighboring Cr‑O clusters, enriched with photogenerated electrons, bind CO2 in a bridging mode that lowers activation barriers. This spatial proximity enables a synchronized proton‑coupled electron transfer cascade, a mechanistic advantage rarely achieved in conventional oxide catalysts.

The performance gains are striking—CH4 and CO outputs surpass 600 µmol g⁻¹ h⁻¹, and the apparent quantum yield reaches 0.38% under 420 nm illumination, aided by a self‑heated surface approaching 200 °C. Such metrics position grain‑boundary‑engineered HEOs as viable candidates for industrial‑scale CO2 recycling, where thermal management and catalyst durability are critical. Future work will likely explore scalable synthesis, integration with solar concentrators, and extension to other multicomponent oxide systems, accelerating the transition toward a circular carbon economy.