Three-Dimensional Porous Indium Single-Atom Catalysts with Improved Accessibility for CO₂ Reduction to Formate

Single-atom catalysts (SACs) present substantial potential in electrocatalytic CO₂ reduction reactions; however, inferior accessibility of single-atom sites to CO₂ limits the overall CO₂RR performances. Herein, we propose to improve the accessibility between In sites and CO₂ through the construction of a three-dimensional (3D) porous indium single-atom catalyst (In₁/NC-3D). The NaCl template-mediated synthesis strategy generates the unique 3D porous nanostructure of In₁/NC-3D. Multiple characterizations validate that In₁/NC-3D exhibits increased exposure of active sites and enhanced CO₂ transport/adsorption capacity compared to the bulk In₁/NC, thus improving accessibility of active sites to CO₂. As a result, the In₁/NC-3D presents superior CO₂RR performance to the bulk In₁/NC, with a partial current density of formate of 67.24 mA cm^-2 at -1.41 V, relative to a reversible hydrogen electrode (vs RHE). The CO₂RR performances with high formate selectivity at a large current density also outperform most reported In-based SACs. Importantly, the In₁/NC-3D is demonstrated to maintain an FE_formate of >82% at -66.83 mA·cm^-2 over 21 h. This work highlights the design of a 3D porous single-atom catalyst for efficient CO₂RR, promoting the development of advanced catalysts toward advanced energy conversion.