Biphase Pd Nanosheets with Atomic-Hybrid RhOx/Pd Amorphous Skins Disentangle the Activity-Stability Trade-Off in Oxygen Reduction Reaction.

The activity-stability trade-off relationship of oxygen reduction reaction (ORR) is a tricky issue that strikes the electrocatalyst population and hinders the widespread application of fuel cells. Here neoteric biphase Pd nanosheets that are structured with ultrathin two-dimensional crystalline Pd inner cores and ≈1 nm thin atomic-hybrid RhOx/Pd amorphous skins, named c/a-Pd@PdRh NSs, for disentangling this trade-off dilemma for alkaline ORR are developed. The superthin amorphous skins significantly amplify the quantity of flexibly low-coordinated atoms for electrocatalysis. An in situ selected oxidation of the top-surface Rh dopants creates atomically hybrid RhOx/Pd disorder surfaces. Detailed energy spectra and theoretical simulation confirm that these RhOx/Pd interfaces can arouse a surface charge redistribution, causing significant electron deficiency and lowered d-band center for surface Pd. Meanwhile, anticorrosive Rh/RhOx species can thermodynamically passivate the neighboring Pd atoms from oxidative dissolution. Thanks to these amplified interfacial effects, the biphase c/a-Pd@PdRh NSs simultaneously exhibit a superhigh ORR activity (5.92 A mg-1, 22.8 times that of Pt/C) and an outstanding long-lasting stability after 100k cycles of accelerated durability test, showcasing unprecedented electrocatalysts for breaking the activity-stability trade-off relationship of ORR. This work paves a bran-new strategy for designing high-performance electrocatalysts through creating modulated amorphous skins on low-dimensional nanomaterials.

Breaking Surface Atomic Monogeneity of Rh2 P Nanocatalysts by Defect-Derived Phosphorus Vacancies for Efficient Alkaline Hydrogen Oxidation.

Breaking atomic monogeneity of catalyst surfaces is promising for constructing synergistic active centers to cope with complex multi-step catalytic reactions. Here, we report a defect-derived strategy for creating surface phosphorous vacancies (P-vacancies) on nanometric Rh2 P electrocatalysts toward drastically boosted electrocatalysis for alkaline hydrogen oxidation reaction (HOR). This strategy disrupts the monogeneity and atomic regularity of the thermodynamically stable P-terminated surfaces. Density functional theory calculations initially verify that the competitive adsorption behavior of Had and OHad on perfect P-terminated Rh2 P{200} facets (p-Rh2 P) can be bypassed on defective Rh2 P{200} surfaces (d-Rh2 P). The P-vacancies enable the exposure of sub-surface Rh atoms to act as exclusive H adsorption sites. Therein, the Had cooperates with the OHad on the peripheral P-sites to effectively accelerate the alkaline HOR. Defective Rh2 P nanowires (d-Rh2 P NWs) and perfect Rh2 P nanocubes (p-Rh2 P NCs) are then elaborately synthesized to experimentally represent the d-Rh2 P and p-Rh2 P catalytic surfaces. As expected, the P-vacancy-enriched d-Rh2 P NWs catalyst exhibits extremely high catalytic activity and outstanding CO tolerance for alkaline HOR electrocatalysis, attaining 5.7 and 14.3 times mass activity that of p-Rh2 P NCs and commercial Pt/C, respectively. This work sheds light on breaking the surface atomic monogeneity for the development of efficient heterogeneous catalysts.

Preparation and Application of a Magnetic Oxidized Micro/Mesoporous Carbon with Efficient Adsorption for Cu(II) and Pb(II).

Water pollution is a worldwide problem that requires urgent attention and prevention and exceeding use of heavy-metal ions is one of the most harmful factors, which poses a serious threat to human health and the ecological environment. In this work, a magnetic oxidized micro/mesoporous carbon (MOMMC) was prepared for the easy separation of Cu(II) and Pb(II) from water. The dual-template method was used to prepare micro/mesoporous carbon using sucrose as the carbon source, silica nanoparticles formed by tetraethyl orthosilicate as the microporous templates, and triblock copolymer F127 as the mesoporous template. MOMMC was obtained by oxidation using potassium persulfate and then magnetized through in situ synthesis of Fe3O4 nanoparticles. FTIR, TG-DSC, XRD, TEM, SEM, nitrogen adsorption-desorption isotherms, zeta potential, and VSM were used to confirm the synthetic process, structure, and basic properties of MOMMC. The high-saturation magnetization (59.6 emu·g-1) of MOMMC indicated its easy and fast separation from water by an external magnetic field. Kinetics studies showed that the adsorption of Cu(II) and Pb(II) on MOMMC fit the pseudo-second-order model well. Isotherm studies showed that the adsorption behavior of Cu(II) was better described by the Langmuir model, and the adsorption behavior of Pb(II) was better described by both Langmuir and Redlich-Peterson models. MOMMC obtained efficient adsorption for Cu(II) and Pb(II) with the large adsorption capacity of 877.19 and 943.40 mg·g-1 according to the Langmuir adsorption isotherm equation, and a better selectivity for Pb(II) was observed in competitive adsorption. MOMMC still possessed a large adsorption capacity for Cu(II) and Pb(II) after three adsorption-desorption cycles. These findings show that MOMMC represents an excellent adsorption material for the efficient removal of heavy-metal ions.

Equilibrated PtIr/IrOx Atomic Heterojunctions on Ultrafine 1D Nanowires Enable Superior Dual-Electrocatalysis for Overall Water Splitting.

Dual-active-sites atomically coupled on ultrafine 1D nanowires (NWs) can offer synergic atomic heterojunctions (AHJs) and high atomic-utilization toward multipurpose and superior catalysis. Here, ≈2-nm-thick PtIr/IrOx hybrid NWs are elaborately synthesized with equilibrated Pt/IrOx AHJs as high-efficiency bifunctional electrocatalysts for overall water splitting. Mechanism studies reveal the atomically coupled Pt-IrOx dual-sites are favorable for facilitating water dissociation, alleviating the binding of H* on Pt sites and inversely regulating the *OH adsorption and oxidation on bridge Ir-Ir sites. By simply equilibrating the Pt-IrOx ratio, the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) can be substantially accelerated. In particular, Pt-rich PtIr/IrOx -30 NWs attain 11-fold enhancements for HER compared to Pt/C in 1.0 m KOH, while IrOx -rich PtIr/IrOx -50 NWs express about five times mass activity referring to Ir/C for OER. Remarkably, the ratio-optimized PtIr/IrOx NWs electrode couple achieves a durably continuous H2 production under a substantially low cell voltage.

Preparation and Performance of Silica-di-Block Polymer Hybrids for BSA-Resistance Coatings.

A series of tem-responsive and protein-resistance property silica-di-block polymers SiO2-g-PMMA-b-P(PEGMA) hybrids are synthesized with methyl methacrylate (MMA) and poly (ethylene glycol) methyl ether methacrylate (PEGMA) by the surface-initiated atom transfer radical polymerization (SI-ATRP). The morphology in tetrahydrofuran (THF) solution, lower critical solution temperature (LCST), surface morphology, bovine serum albumin (BSA)-resistance property, and thermal stability of nanoparticles were analyzed. The results of 1H-NMR, GPC, and TEM prove that the silica-di-block hybrids have been obtained. The silica-di-block hybrids shows the LCST (52-64 °C) in aqueous solution. The hybrid films casted by THF present distributed uniform granular bulges and the film surface is relatively smooth (Ra = 15.4 nm ~ 10.5 nm). The results of QCM-D showed that only a small amount of BSA protein(△f = 18.6 ~ 11.8 Hz) was adsorbed on the surface of the films. The result of XPS also demonstrated that only a small amount of BSA protein was absorbed onto the surface of the film (N% = 1.86). The TGA analyses indicate that the thermal decomposition temperature of hybrids is 288 °C. Thus, it is suggested that the hybrids are served as a suitable coating with BSA resistance property and thermal stability.

Synthesis and comparison of two poly (methyl methacrylate-b-3-(trimethoxysilyl)propyl methacrylate)/SiO2 hybrids by "grafting-to" approach.

Two copolymer/SiO2 hybrids are prepared by growing SiO2 on the template of well -structured diblock copolymer PMMA-b-PMPS using a "grafting-to" approach. PMMA-b-PMPS is obtained by atom transfer radical polymerization (ATRP) of methyl methacrylate (PMMA) and 3-(trimethoxysilyl)propyl methacrylate (PMPS) using a brominated initiator end group termed 1H,1H,2H,2H-heptadecafluoro (F-Br) and a conventional initiator of ethyl 2-bromoisobutyrate (EBiB), respectively. The "grafting-to" approach is controlled at HCl for 24h by hydrolysis and condensation of Si(OCH3)3 groups in PMPS with tetraethyl orthosilicate (TEOS) to gain both hybrids of F-PMMA-b-PMPS/SiO2 (by F-Br initiator) and E-PMMA-b-PMPS/SiO2 (by EBIB initiator). Comparatively, a little amount of fluorine content provided by F-Br is able to tighten the size of self-assembled micelles, to improve wettability and the viscoelasticity of F-PMMA-b-PMPS film due to F-Br migrating onto the film surface. Therefore, the surface of F-PMMA-b-PMPS film is sufficiently hydrophobic (99° and Δf=2941Hz) than E-PMMA-b-PMPS film (94°and Δf=4820Hz), and the viscoelasticity of the adsorbed layer for F-PMMA-b-PMPS (ΔD/Δf=-0.112) film is much harder than E-PMMA-b-PMPS/SiO2 (ΔD/Δf=-0.071). On the other hand, the cross-linked silica in PMMA-b-PMPS/SiO2 could also increase water contact angels of films (100-107°) and decrease the water absorption (Δf=704-798Hz). The influence on the viscoelasticity of the adsorbed layer by the fluorine group is much more obvious than the cross-linked silica, therefore F-PMMA-b-PMPS/SiO2 (ΔD/Δf=-0.347) and F-PMMA-b-PMPS (ΔD/Δf=-0.112) films have harder adsorbed layer than E-PMMA-b-PMPS/SiO2 (-0.071) and F-PMMA-b-PMPS films (-0.042). However, compared with a slightly improvement in thermo stability by F-Br, the cross-linked silica in PMMA-b-PMPS/SiO2 performs significantly improving thermal decomposition temperature at 300°C and 350°C.