The development of highly efficient bifunctional catalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is crucial for improving the efficiency of the Zn–air battery. Herein, we report porous NiO/CoN interface nanowire arrays (PINWs) with both oxygen vacancies and a strongly interconnected nanointerface between NiO and CoN domains for promoting the electrocatalytic performance and stability for OER and ORR. Extended X-ray absorption fine structure spectroscopy, electron spin resonance, and high-resolution transmission electron microscopy investigations demonstrate that the decrease of the coordination number for cobalt, the enhanced oxygen vacancies on the NiO/CoN nanointerface, and strongly coupled nanointerface between NiO and CoN domains are responsible for the good bifunctional electrocatalytic performance of NiO/CoN PINWs. The primary Zn–air batteries, using NiO/CoN PINWs as an air–cathode, display an open-circuit potential of 1.46 V, a high power density of 79.6 mW cm–2, and an energy density of 945 Wh kg–1. The three-series solid batteries fabricated by NiO/CoN PINWs can support a timer to work for more than 12 h. This work demonstrates the importance of interface coupling and oxygen vacancies in the development of high-performance Zn–air batteries.Keywords: nanointerface; NiO/CoN porous nanowires; oxygen evolution; oxygen vacancies; Zn−air battery;

AbstractThe exploration of highly efficient nonprecious metal bifunctional electrocatalysts to boost oxygen evolution reaction and oxygen reduction reaction is critical for development of high energy density metal-air batteries. Herein, a class of CuS/NiS2 interface nanocrystals (INs) catalysts with atomic-level coupled nanointerface, subtle lattice distortion, and plentiful vacancy defects is reported. The results from temperature-dependent in situ synchrotron-based X-ray absorption fine spectroscopy and electron spin resonance spectroscopy demonstrate that the lattice distortion of 14.7% in CuS/NiS2 caused by the strong Jahn–Teller effect of Cu, the strong atomic-level coupled interface of CuS and NiS2 domains, and distinct vacancy defects can provide numerous effective active sites for their excellent bifunctional performance. A liquid Zn-air battery with the CuS/NiS2 INs as air electrode displays a large peak power density (172.4 mW cm−2), a high specific capacity (775 mAh gZn−1), and long cycle life (up to 83 h), making the CuS/NiS2 INs among the best bifunctional catalysts for Zn-air battery. More remarkably, the flexible CuS/NiS2 INs-based solid-state Zn-air batteries can power the LED after twisting, making them be promising in portable and wearable electronic devices.

AbstractThe development of highly active and stable oxygen evolution reaction (OER) electrocatalysts is crucial for improving the efficiency of water splitting and metal–air battery devices. Herein, an efficient strategy is demonstrated for making the oxygen vacancies dominated cobalt–nickel sulfide interface porous nanowires (NiS2/CoS2–O NWs) for boosting OER catalysis through in situ electrochemical reaction of NiS2/CoS2 interface NWs. Because of the abundant oxygen vacancies and interface porous nanowires structure, they can catalyze the OER efficiently with a low overpotential of 235 mV at j = 10 mA cm−2 and remarkable long-term stability in 1.0 m KOH. The home-made rechargeable portable Zn–air batteries by using NiS2/CoS2–O NWs as the air–cathode display a very high open-circuit voltage of 1.49 V, which can maintain for more than 30 h. Most importantly, a highly efficient self-driven water splitting device is designed with NiS2/CoS2–O NWs as both anode and cathode, powered by two-series-connected NiS2/CoS2–O NWs-based portable Zn–air batteries. The present work opens a new way for designing oxygen vacancies dominated interface nanowires as highly efficient multifunctional electrocatalysts for electrochemical reactions and renewable energy devices.

A rational design of highly active and robust catalysts based on earth-abundant elements for hydrogen evolution reaction (HER) is essential for future renewable energy applications. Herein, we report the synthesis of a new class of ultrathin metallic CuFeS2 nanosheets (NSs) with abundant exposed high-index {04} facets. They serve as a robust catalyst for the HER with a lower onset potential of 28.1 mV, an overpotential of only 88.7 mV (at j = 10 mA cm−2) and remarkable long-term stability in 0.5 M H2SO4, which make them the best system among all the reported non-noble metal catalysts. The theoretical calculations reveal that the mechanistic origin for such a high HER activity should be attributed to the excess S2− active sites on the exposed {04} high-index facets of CuFeS2 NSs, which have a rather favorable Gibbs free energy for atomic hydrogen adsorption. The present work highlights the importance of designing ultrathin metallic chalcopyrite nanosheets with high-index facets in order to increase the number of active sites for boosting the HER performance.

We report a facile nitrogenation/exfoliation process to prepare hybrid Ni–C–N nanosheets. These nanosheets are <2 nm thin, chemically stable, and metallically conductive. They serve as a robust catalyst for the hydrogen evolution reaction in 0.5 M H2SO4, or 1.0 M KOH or 1.0 M PBS (pH = 7). For example, they catalyze the hydrogen evolution reaction in 0.5 M H2SO4 at an onset potential of 34.7 mV, an overpotential of 60.9 mV (at j = 10 mA cm–2) and with remarkable long-term stability (∼10% current drop after 70 h testing period). They are promising as a non-Pt catalyst for practical hydrogen evolution reaction.

Water splitting via the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in producing H2 and O2 is a very important process in the energy field. Developing an efficient catalyst which can be applied to both HER and OER is crucial. Here, a bifunctional catalyst, CFP/NiCo2O4/Co0.57Ni0.43LMOs, has been successfully fabricated. It exhibits remarkable performance for OER in 0.1 M KOH producing a current density of 10 mA cm−2 at an overpotential of 0.34 V (1.57 V vs. RHE), better than that of the commercial Ir/C (20%) catalyst. Simultaneously, it also exhibits good catalytic performance for HER in 0.5 M H2SO4 producing a current density of 10 mA cm−2 at an overpotential of 52 mV and a Tafel slope of 34 mV dec−1, approaching that of the commercial Pt/C (20%) nanocatalyst. Particularly, CFP/NiCo2O4/Co0.57Ni0.43LMOs present better durability under harsh OER and HER cycling conditions than commercial Ir/C and Pt/C. Furthermore, an H-type electrolyzer was fabricated by applying CFP/NiCo2O4/Co0.57Ni0.43LMOs as the cathode and anode electrocatalyst, which can be driven by a single-cell battery. This bifunctional catalyst will be very promising in overall water splitting.

The synthesis of semiconducting nanoplates (NPs) with defined crystal phase is of particular interest, especially their intriguing properties related to the size, shape, and crystal phase. Herein, a liquid-state transformation process from hexagonal-phase CuS NPs is employed to fabricate the cubic-phase Cu2S NPs. The CuS NPs were converted into Cu2S NPs but maintained the morphology. The Cu2S NPs exhibit better oxygen evolution reaction (OER) activity than CuS NPs. Furthermore, the OER activity of Cu2S NPs can be improved by the addition of a glycine (Gly) solution. The Cu2S NPs with Gly in a phosphate buffer solution exhibit excellent OER activity and durability, which approaches that of the best known commercial Ir/C (20%) nanocatalyst. In this work, a good strategy for fabricating a noble-metal-free OER catalyst has been proposed, which could provide insight into developing new water oxidation catalysts with high activity.

CuS nanocrystals are potential materials for developing low-cost solar energy conversion devices. Understanding the underlying dynamics of photoinduced carriers in CuS nanocrystals is essential to improve their performance in these devices. In this work, we investigated the photoinduced hole dynamics in CuS nanodisks (NDs) using the combination of transient optical (OTA) and X-ray (XTA) absorption spectroscopy. OTA results show that the broad transient absorption in the visible region is attributed to the photoinduced hot and trapped holes. The hole trapping process occurs on a subpicosecond time scale, followed by carrier recombination (∼100 ps). The nature of the hole trapping sites, revealed by XTA, is characteristic of S or organic ligands on the surface of CuS NDs. These results not only suggest the possibility to control the hole dynamics by tuning the surface chemistry of CuS but also represent the first time observation of hole dynamics in semiconductor nanocrystals using XTA.

We report a facile modification of graphene oxide (GO) by gelatin to mimic charged proteins present in the extracellular matrix during bone formation. The bioinspired surface of GO–gelatin (GO–Gel) composite was used for biomimetic mineralization of hydroxyapatite (HA). A detailed structural and morphological characterization of the mineralized composite was performed. Additionally, MC3T3-E1 cells were cultured on the GO–Gel surfaces to observe various cellular activities and HA mineralization. Higher cellular activities such as cell adhesion, cell proliferation, and alkaline phosphatase activity (ALP) were observed on the GO–Gel surface compared with the GO or glass surface. The increase of ALP confirms that the proposed GO–Gel promotes the osteogenic differentiation of MC3T3-E1 cells. Moreover, the evidence of mineralization evaluated by scanning electron microscopy (SEM) and alizarin red staining (ARS) corroborate the idea that a native osteoid matrix is ultimately deposited. All these data suggest that the GO–Gel hybrids will have great potential as osteogenesis promoting scaffolds for successful application in bone surgery.

In bone tissue engineering, it is imperative to design multifunctional biomaterials that can induce and assemble bonelike apatite that is close to natural bone. In this study, graphene oxide (GO) was functionalized by carrageenan. The resulting GO-carrageenan (GO-Car) composite was further used as a substrate for biomimetic and cell-mediated mineralization of hydroxyapatite (HA). It was confirmed that carrageenan on the GO surface facilitated the nucleation of HA. The observation of the effect of the GO-Car on the adhesion, morphology, and proliferation of MC3T3-E1 cells was investigated. In vitro studies clearly show the effectiveness of GO-Car in promoting HA mineralization and cell differentiation. The results of this study suggested that the GO-Car hybrid will be a promising material for bone regeneration and implantation.Keywords: Biomimetic mineralization; carrageenan; cell-mediated; graphene oxide; hydroxyapatite;

A rhodamine-based probe bearing an N,N-dimethylaniline unit was developed as a fluorescent chemodosimeter for Ce4+ in aqueous media. Importantly, the sensor can selectively respond to Ce4+ over other commonly coexistent metal ions (such as La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Er3+, Tb3+, Ho3+, Tm3+, Yb3+, Lu3+, Y3+) in aqueous media with a rapid response time. The system, which utilizes an irreversible Ce4+-promoted oxidation reaction, responds instantaneously at room temperature with linear proportionality to the amount of Ce4+.Graphical abstractA selective rhodamine-based probe was developed as a fluorescent chemodosimeter for Ce4+ in aqueous media.Highlights► A new rhodamine derived fluorescent probe has been synthesized. ► The probe offers highly selective and sensitive detection of Ce4+ ions over common related ions. ► The probe undergoes an oxidative cyclization and a concomitant oxidative ring opening process upon reaction with the Ce4+, resulting in both the color and turn-on fluorescence changes.

In this study, monodisperse palladium (Pd) nanoparticles on reduced graphene oxide (RGO) surfaces were successfully prepared by a “wet” and “clean” method in aqueous solution. Without any surface treatment, Pd nanoparticles are firmly attached to the RGO sheets. These RGO/Pd nanocomposites exhibited catalytic activity in hydrogen generation from the hydrolysis of ammonia borane (AB). Their hydrolysis completion time and activation energy were 12.5 min and 51 ± 1 kJ mol−1, respectively, which were comparable to the best Pd-based catalyst reported. The TOF values (mol of H2 × (mol of catalyst × min)−1) of RGO/Pd is 6.25, which appears to be one of the best catalysts reported so far. We also obtained a 11B NMR spectrum to investigate the mechanism of this catalytic hydrolysis process. This simple and straightforward method is of significance for the facile preparation of metal nanocatalysts with high catalytic activity on proper supporting materials.

A Fe3+ chemosensor L1 was successfully synthesized with a quinoline moiety bound to rhodamine 6G hydrazide. The sensor L1 shows high selectivity and sensitivity to Fe3+ in aqueous solution in the presence of other trace metal ions in organisms, abundant cellular cations and prevalent toxic metal ions in the environment. In addition, biological imaging and micro computed tomography (MCT) technology studies have demonstrated that L1 could act as a turn-on fluorescent chemosensor for Fe3+ in living cells.

A Fe3+ chemosensor L1 was successfully synthesized with a quinoline moiety bound to rhodamine 6G hydrazide. The sensor L1 shows high selectivity and sensitivity to Fe3+ in aqueous solution in the presence of other trace metal ions in organisms, abundant cellular cations and prevalent toxic metal ions in the environment. In addition, biological imaging and micro computed tomography (MCT) technology studies have demonstrated that L1 could act as a turn-on fluorescent chemosensor for Fe3+ in living cells.