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COoking with gas Low concentrations of carbon monoxide (CO) have shown therapeutic benefit in preclinical models, but safe delivery of appropriate dose has been challenging to achieve. Here, inspired by molecular gastronomy, Byrne et al . designed gas-entrapping materials (GEMs) using components generally recognized as safe, including xanthan gum, methylcellulose, maltodextrin, and corn syrup. Solid, hydrogel, and foam GEMs containing CO could deliver different concentrations of the gas to healthy rodents and pigs through noninhaled routes. In rodent models of colitis, acetaminophen overdose, and radiation-induced proctitis, rectally administered foam GEMs reduced tissue injury and inflammation. Foam GEMs could help achieve safe therapeutic CO delivery. 

Au is one of the most promising electrocatalysts to convert CO 2 into CO in an aqueous-phase electrochemical reduction. However, ultrasmall Au nanocatalysts (AuNCs, <2 nm) have proven to be favorable for water reduction over CO 2 , although they possess a large surface-to-volume ratio and potentially are ideal for CO 2 reduction. We herein report that ultrasmall AuNCs (1.9 ± 0.3 nm) supported on nitrided carbon are remarkably active and selective for CO 2 reduction. The mass activity for CO of AuNCs reaches 967 A g −1 with a faradaic efficiency for CO of ∼83% at −0.73 V ( vs . reversible hydrogen electrode) that is an order of magnitude more active than the state-of-the-art results. The high activity is endowed by the large surface area per unit weight and the high selectivity of ultrasmall AuNCs for CO 2 reduction originates from the cooperative effect of Au and the nitrided carbon support where the surface N sites act as Lewis bases to increase the surface charge density of AuNCs and enhance the localized concentration of CO 2 nearby catalytically active Au sites. We show that our results can be applied to other pre-synthesized Au catalysts to largely improve their selectivity for CO 2 reduction by 50%. Our method is expected to illustrate a general guideline to effectively lower the cost of Au catalysts per unit weight of the product while maintaining its high selectivity for CO 2 reduction.