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• Engineering of Ru atomic structure by fine-tuning Cl and Co coordination. • Acid-leaching of bimetallic catalyst for a 4.1-fold increase of H 2 generation rate. • Cl geometric effects of site blockage and steric hindrance as the main factors. • Kinetics switch from a Cl coverage-limited to a reactant activation regime. Herein, we demonstrate a strategy of engineering Ru atomic structures by fine-tuning Cl and Co coordination to synergize the quantity and quality of Ru active sites for boosting hydrogen generation from ammonia borane hydrolysis, via engineering the Cl-free/Cl-containing monometallic Ru catalysts and Co-leaching/Co-containing bimetallic Ru-Co catalysts. Under similar Ru particle sizes, the correlation between Ru binding energy and hydrogen generation activity affords a quantitative discrimination of Ru electronic and geometric contributions, where the site blockage and steric hindrance of Ru by Cl are more detrimental to hydrogen generation compared with the electronic modification by charge donation from Co to Ru. Reversely, the acid-leaching of Co from bimetallic catalysts creates abundant edge-like Ru active sites with much lower H 2 O activation barrier, as indicated by the kinetics switch from a Cl coverage-limited regime to a reactant activation regime, thus yielding a significant 4.1-fold increase in hydrogen generation activity. [ABSTRACT FROM AUTHOR]

• Denitrification rates are significantly enhanced by nanoplastics in wetland soils. • NirS bacterial community regulates the denitrification response of nanoplastic group. • Nanoplastics induce denser denitrifier networks and cause shifts in keystone species. • Nanoplastics may be a more potent driver of denitrification than microplastics. With the widespread presence of plastic waste in ecosystems, it is imperative to understand the response of natural processes to micro- and nanoplastic pollution pressures. However, the effects of nanoplastics on biogeochemical cycles are still overlooked and controversial. This study investigated the effects of three particle sizes (100 μm, 7 μm, and 80 nm) of polystyrene (PS) micro/nanoplastics (0.08 % of mass concentration) on denitrification processes and nirS / nirK denitrifying bacterial communities in wetland soils. The results indicated that PS nanoplastics were found to significantly enhance denitrification rates from 21.30 to 54.73 μmol N 2 ·h−1·kg−1, increasing by 1.57 times compared to the control. Exposure to nanoplastics caused shifts in the composition and structure of the nirS -type denitrifier community. LEfSe analysis, random forest, and Mantel tests revealed that nirS denitrifying bacteria, especially Sideroxydans , played a pivotal role in driving denitrification rates (Mantel's R = 0.24, p = 0.002), likely due to the faster release of organic substrates from nanoplastics. Microbial co-occurrence networks demonstrated that nanoplastic amendments fostered a denser denitrifier network and led to shifts in keystone species. Sideroxydans appeared more likely to cooperate with other bacteria, such as Burkholderiales , to complete denitrification processes. This study suggests that nanoplastics are a potentially stronger driver of denitrification than microplastics, providing insight into the impact of plastic pollutants on biogeochemical cycling in natural wetland ecosystems. Given the widespread distribution of wetlands, the potential increase in gaseous nitrogen emissions due to nanoplastics pollution warrants attention. [Display omitted] [ABSTRACT FROM AUTHOR]