NiO-dispersed small-sized Pt/Mg₂Al₄Si₅O₁₈ as a high-performance and robust catalyst for formaldehyde purification

Commercial Mg₂Al₄Si₅O₁₈ cordierite materials are extensively employed in catalytic reactions due to their outstanding high-temperature stability and low thermal expansion coefficient. Nevertheless, the limited specific surface area of these materials presents a significant challenge for the preparation of small-sized Pt nanoparticles. In this work, we achieved the preparation of ∼3 nm Pt nanoparticles on commercial Mg₂Al₄Si₅O₁₈ cordierite with an ultralow specific surface area via NiO modification. The research results indicate that appropriate amounts of NiO modification can notably enhance the activity and stability of the Pt/Mg₂Al₄Si₅O₁₈ catalyst. During a 20 h long-term stability test at 60 °C under a weight hourly space velocity (WHSV) of 30,000 mL/(g⋅h) and relative humidity (RH) of 25 %, the 6NiO-1Pt/Mg₂Al₄Si₅O₁₈ and 9NiO-1Pt/Mg₂Al₄Si₅O₁₈ catalysts (with ∼3 nm Pt nanoparticles) achieve stable HCHO conversions of 91.5 %-96.7 % and 93.4 %-100 %, respectively. Comprehensive characterization studies disclose that there is a distinct interaction between Pt and NiO, which increases the dispersion of Pt. This interaction also greatly improves the adsorption and activation of O₂ and HCHO, enhances the mobility of O₂, and strengthens the adsorption of dioxymethylene (DOM) intermediate species. These factors are the key reasons for the significant enhancement of the catalytic performance of Pt/Mg₂Al₄Si₅O₁₈ catalysts after NiO modification. Additionally, we propose a possible reaction process where formaldehyde reacts with OH and oxygen species, and is then gradually oxidized to CO₂ via dioxymethylene (DOM), formate species, and CO on 9NiO-1Pt/Mg₂Al₄Si₅O₁₈ catalyst.