The bi-atom catalysts (BACs) have attracted increasing attention in important electrocatalytic reactions such as oxygen reduction reaction (ORR). Here, by means of density functional theory simulations coupled with machine-learning technology,...

Single cobalt atoms supported by a defective two-dimensional boron nitride material catalyze the ORR via a direct 4e− pathway with a largest activation barrier of 0.3 eV.

Two-dimensional boron nitride (2D-BN) materials doped with metallic atoms are suitable candidates for the oxygen reduction reaction (ORR) to replace Pt-based catalysts. In this study, a series of model 2D-BN materials doped with metallic atoms were designed to uncover the relationship between ORR activity and metallic dopants. A volcano curve correlation was derived between ORR overpotential and the adsorption free energy values of *OH. Only the doped structures, located at the top of the volcano curve, exhibit optimized activity. Through analyzing the dynamic results, the ORR was found to occur only via the 4e- pathway on Co doped 2D-BN materials with the activation energy of 0.30 eV, which is lower than that achieved with the state-of-the-art Pt-based catalysts (0.79 eV). Furthermore, based on the calculations of electronic structure properties, we find that the small highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap is more beneficial to the 4e- pathway and prove that the binding strength between metallic atoms-doped 2D-BN materials and oxygenated intermediates is regulated by the HOMO of the metallic dopant consisting non-bonding or delocalized orbitals. These results provide an effective method to facilitate the design of new BN-based materials with high electrocatalytic performances besides the ORR performance.

The sub-nanocluster metal catalysts exhibit outstanding activities for a variety of catalytic reactions. Here, from density functional theory (DFT) simulations, we systematically explored the potential of an experimentally well-defined Au22(L8)6 nanocluster (where L8 = 1,8-bis­(diphenylphosphino)) as an electrocatalyst to accelerate the sluggish kinetics of the oxygen reduction reaction (ORR) in fuel cells. Especially, the Au22(L8)6 nanocluster with the exposure of in situ coordination unsaturated (cus) Au is able to avoid the block effect of the ligands and exhibits excellent activity in electrocatalysis. The DFT results showed that the cus Au atoms are the active sites for O2 activation, and all of the ORR intermediates can favorably bind with the cus Au. Notably, the 2e– reduction on Au22(L8)6 is unfavorable since the generated H2O2 species would decompose into two OH species spontaneously. Instead, ORR prefers to proceed via the 4e– pathway to form H2O and the predicted overpotential is 0.49 V, which is comparable to that of the Pt-based catalysts (0.40 V). The extended gold surfaces, e.g., Au(111), Au(100), Au(110), and Au(211), are also investigated for comparison. Their ORR activities are found to be much lower than that for Au22(L8)6. The activity trend, Au22(L8)6 (0.49 V) > Au(211) (0.70 V) > Au(110) (0.82 V) > Au(100) (0.92 V) > Au(111) (1.22 V), was justified by the geometry descriptor of the generalized coordination number of Au. Our results show the promising activity of Au22(L8)6 for ORR and would stimulate the design of novel and highly efficient sub-nanocluster electrocatalysts.

Single metal atom supported by a defective two-dimensional boron nitride material is a promising ORR catalyst.

Herein we report a soy protein isolate/pectin binary complex particle to stabilize emulsion (olive oil served as dispersed phase) containing quercetin. FTIR was conducted to confirm successful preparation of emulsion before and after embedding quercetin. CLSM was used to determine the microstructure and zeta-potential, rheological behavior, storage stability and freeze-thaw stability were analyzed and were correlated with pH condition. Olive oil-soy protein isolate/pectin emulsion at pH 3.0 can remain stable after 30 days’ storage and exhibited greatest freeze-thaw stability after 3 cycles. Quercetin availability was evaluated by in vitro gastrointestinal digestion experiments and it reached 15.94% at pH 7.0.

Considering the promising prospects of Au25(SR)18 q and its alloy clusters in numerous fundamental catalysis research studies derived from their well-defined structures, developing a deep understanding of the structure–property correlation becomes significantly urgent. Herein, we explored a prototype [Au25(SR)18] q cluster, monoatom-doped bimetallic [MAu24(SR)18] q clusters (M = Pt, Pd, Ag, Cu, Hg, or Cd), and their singly deligated M-exposure and S-exposure systems as electrocatalysts toward O2 reduction reaction (ORR) at the acidic medium. Theoretical simulations reveal that the fully ligand-protected clusters prefer H2O2 formation through the two-electron (2e–) mechanism, whereas the dethiolated clusters prefer to proceed via the four-electron (4e–) pathway for H2O production. Among them, a single Hg substitution at the staple site, namely, fully ligated [HgAu24(SCH3)18]0–O and dethiolated [HgAu24(SCH3)17]0–O with an exterior −SCH3 removal has great potential to realize high-efficiency 2e– and 4e– ORR, with an ultralow overpotential of 0.08 and 0.43 V, respectively. The correlation between adsorption of oxygenated intermediates and Bader charge as well as active metal d-band center sheds light on the underlying origin of selectivity and activity. Besides, the analysis of projected density of states suggests that monoatom doping has a mild modification to the s-bands of Au, but the removal of the −SR ligand can obviously amend the electronic structure of Au-s states. Particularly, in contrast to the strong d-electron effect in Au25 q and other doped MAu24 q clusters, the s-electron effect from the staple-doped Hg atom shows great promise in optimizing the intermediate adsorption and functions as a distinguished electrocatalyst for O2 reduction. These insights provide useful guidelines for the design of high-efficiency metal nanocluster electrocatalysts by implementing late-transition metal or p-block metal with a strong s- or p-electron effect to achieve superior ORR activity.

Compared with the well-established metal−thiolate interfaces, the study of the interface between N-heterocyclic carbenes (NHCs) and the metal substrate is much less explored, and the majority of work has been limited to the surfaces of Au, Ag, and Cu. The interface is closely related to the combination modes of NHCs on solid surfaces, which determines the morphologies of NHC-based self-assembly monolayers (SAMs). In this work, we performed theoretical investigations to take a fundamental look at how the methylated carbene (NHC Me ) ligands bind to the different solid surfaces (Au111, Ag111, Cu111, Ti0001, Pt111, Ru0001, and H-terminated Si111). On the clean surfaces without adatoms, the NHC Me vertically binds with surface atoms by a single C−M bond. Compared with the experimentally characterized NHC−Au(111) interface, the stronger adsorption of NHC Me on Pt (111) and Ti (0001) and the comparable binding strength on Ru (0001) indicate that they hold great promise to form highly strong and stable SAMs. Moreover, on the adatom surfaces, a dimer complex, NHC Me −M ad −NHC Me , can be formed and is energetically more favored than the upright adsorption. Interestingly, the distance of adatoms from the surface, which is an intrinsic property of the transition metals, plays an important role in determining the molecular orientations of NHC Me . The longer distance of coinage adatoms results in a nearly flatlying "T-shaped" binding mode. By contrast, the shorter distance of adatoms on Pt (111) and Ru (0001) brings a winglike "Vshaped" configuration, which has thus far not been revealed in experiment. The results will invite the experimental design of stable NHC-based SAMs with attractive interface features beyond the coinage metals.