> ## Content Index > Fetch the complete content index at: https://research-pop.com/llms.txt > Use this file to discover other available public pages before exploring further. # Nanjing University, Shandong Normal University and UC Riverside teams use water to redirect NO–CO chemistry towards ammonia - URL: https://research-pop.com/nanjing-university-shandong-normal-university-and-uc-riverside-teams-use-water-to-redirect-no-co-chemistry-towards-ammonia/ - Published: 2026-09-26T12:05:28.000Z - Updated: 2026-09-26T12:05:28.000Z - Author: ResearchPOP - Tags: Chemistry ![](https://storage.ghost.io/c/7c/5e/7c5e0911-739b-4a35-94eb-3e810bf78ba7/content/images/2026/09/Screenshot-2026-09-26-at-13.17.11.png) ## At a glance The reaction between nitric oxide and carbon monoxide is commonly used to remove both pollutants by converting NO mainly into N₂ and CO into CO₂. Researchers from Nanjing University, Shandong Normal University and the University of California, Riverside show that adding water can redirect this established chemistry towards NH₃ over supported CuOₓ clusters. With water in the feed, the temperature required for 50% conversion falls from 361 to 291 °C, while the apparent activation energy decreases from 133 to 25 kJ mol⁻¹. Operando spectroscopy, feed-switching experiments and density-functional-theory calculations identify surface isocyanate, NCO∗, as the point at which the dry and wet pathways diverge. Under dry conditions, NCO∗ continues along a route associated with N₂ formation. In the presence of water, hydrolysis of this intermediate introduces oxygen- and hydrogen-containing surface species and opens a lower-barrier sequence towards NH₃. The study places water within the reaction mechanism rather than treating it only as a component of the exhaust stream. ## Background Nitric oxide and carbon monoxide are harmful gases associated with combustion exhaust. Catalytic NO–CO reactions can remove both at once because CO acts as a reductant for NO and is itself oxidized to CO₂. The conventional target is nitrogen, which returns the nitrogen atom to a stable, non-toxic molecular form. The surface chemistry is not a direct exchange between the two gas molecules. NO can adsorb and form nitrogen-containing intermediates, while CO interacts with adsorbed oxygen and nitrogen species. One important intermediate is surface isocyanate, NCO∗, which can connect several product pathways. Water is often present in realistic gas streams. It can compete for adsorption sites, hydroxylate an oxide surface or supply hydrogen through dissociation and proton transfer. These effects may inhibit, accelerate or redirect a reaction. Producing NH₃ from NO requires N–H bond formation, making water-derived hydrogen species especially relevant. Supported metal-oxide clusters provide an interface where these steps can occur near one another. Their behaviour can differ from that of isolated ions or large oxide crystals because neighbouring copper and oxygen sites can jointly adsorb and transform NO, CO, H₂O and their intermediates. The present study examines whether this nanoscale environment allows water to hydrolyse NCO∗ before it follows the conventional dry pathway. ## Research question How does water change the fate of surface NCO∗ on supported CuOₓ clusters, and can that change sustain NH₃ formation from NO and CO under defined feed conditions? ## Inside the study The researchers first connected catalytic behaviour with the form of copper present on alumina. The most active material, described as 5Cu/Al, contains highly dispersed CuOₓ clusters approximately 1–2 nm across. This intermediate structural regime provides neighbouring sites for the simultaneous adsorption and transformation of NO, CO, water and surface intermediates without forming large crystalline copper-oxide particles. Introducing water produced a marked change in the temperature dependence of the reaction. The temperature for 50% conversion decreased from 361 to 291 °C, and the apparent activation energy fell from 133 to 25 kJ mol⁻¹. NH₃ appeared at or below 275 °C, a region in which the dry feed continued to favour the conventional NO–CO chemistry more strongly. These comparisons establish that water changes both the reaction rate and the product pathway. Operando diffuse-reflectance infrared Fourier-transform spectroscopy followed the adsorbed species while NO and CO were supplied to the catalyst. The spectra detected surface NCO∗, placing the isocyanate intermediate within the working reaction network. Rather than identifying its presence alone, the team used changes in the feed to examine what happened to it next. During feed-switching experiments, the addition of water changed the rate and manner in which the NCO∗ signal was consumed. The accompanying spectral changes support the participation of hydroxyl- and hydrogen-containing species in hydrolysis and subsequent N–H bond formation. In the authors' interpretation, water supplies the chemistry needed to move the nitrogen atom from an isocyanate environment towards ammonia. Density-functional-theory calculations compare the competing fates of the same intermediate. Under dry conditions, NCO∗ reacts with NO along the proposed route towards N₂. The calculated barrier for this step is 2.61 eV. When water is included, hydrolysis of NCO∗ opens a sequence towards NH₃ with a key calculated barrier of 1.27 eV. The lower barrier is consistent with the experimentally observed decrease in apparent activation energy, although the experimental and calculated values describe different levels of the reaction system and should not be equated directly. The resulting mechanism places NCO∗ at a branch point. Without water, the intermediate remains connected to the nitrogen-forming reaction network. With water, its C–N–O unit can be hydrolysed and hydrogenated through surface steps that ultimately release NH₃. CO continues to contribute to the redox chemistry, while water provides a route for introducing hydrogen without an external H₂ feed. The authors also examined whether the ammonia-forming state could be maintained. At 350 °C, the catalyst sustained an NH₃ concentration of approximately 250 ppm during a 50 h run. Under a feed containing 4,000 ppm CO, 1,000 ppm NO and 5% water, NH₃ selectivity reached 60% at 450 °C. These results refer to different reported reaction conditions and describe concentration, selectivity and stability rather than one interchangeable performance metric. Feed composition remains important. The article reports that oxygen suppresses the target chemistry, defining a practical boundary because many exhaust streams contain residual O₂ alongside water. Taken together, the structural, spectroscopic and computational evidence supports a connected account. Dispersed CuOₓ clusters create neighbouring reaction sites, NO and CO form surface NCO∗, and water changes the next step by enabling hydrolysis. The altered intermediate chemistry lowers the apparent kinetic demand and directs part of the nitrogen-containing flux towards NH₃ instead of the conventional N₂ product. ## Takeaways and outlook The study shows that water can act as a reactant and pathway selector in NO–CO conversion. Its central role is not limited to changing surface hydration. Water redirects a detected NCO∗ intermediate towards N–H bond formation and ammonia through a lower-barrier calculated pathway. The result also highlights the importance of the CuOₓ cluster size and dispersion. The 1–2 nm clusters provide a working environment in which adsorption, hydrolysis and redox steps can be coordinated. Operando infrared measurements connect that environment with the surface intermediate, while calculations compare the dry and water-assisted branches. Future development will need to address oxygen tolerance, ammonia yield under realistic mixed feeds and control over competing nitrogen products. The paper provides a mechanistic starting point by identifying which intermediate is redirected and which feed component enables the change. ## About the researchers Wei Tan (Nanjing University) and Xueqing Liu (Shandong Normal University) are equal first authors. Wei Tan (Nanjing University), Chuanzhi Sun (Shandong Normal University) and Fudong Liu (University of California, Riverside) are the corresponding authors. The other authors are Jiawei Yang, Xiaoyu Ji, Ge Yao and Lin Dong (Nanjing University), and Kailong Ye and Shaohua Xie (University of California, Riverside). ## Original research Wei Tan; Xueqing Liu; Jiawei Yang; Xiaoyu Ji; Kailong Ye; Shaohua Xie; Ge Yao; Chuanzhi Sun; Fudong Liu; Lin Dong. “Water-Enabled Conversion of NO and CO to NH₃ over CuOₓ Clusters via Hydrolysis of Surface –NCO Intermediates.” *Journal of the American Chemical Society* (2026). [https://doi.org/10.1021/jacs.6c05012](https://doi.org/10.1021/jacs.6c05012?ref=research-pop.com). --- ## Research POP Notes This article reflects the independent interpretation of the Research POP team and does not represent the views of the authors, their institutions or the journal. 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