The 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 (NiS /CoS -O NWs) for boosting OER catalysis through in situ electrochemical reaction of NiS /CoS 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 and remarkable long-term stability in 1.0 m KOH. The home-made rechargeable portable Zn-air batteries by using NiS /CoS -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 NiS /CoS -O NWs as both anode and cathode, powered by two-series-connected NiS /CoS -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.

Two-dimensional (2D) metal-organic framework (MOF) nanosheets have been recently regarded as the model electrocatalysts due to their porous structure, fast mass and ion transfer through the thickness, and large portion of exposed active metal centers. Combining them with electrically conductive 2D nanosheets is anticipated to achieve further improved performance in electrocatalysis. In this work, we in situ hybridized 2D cobalt 1,4-benzenedicarboxylate (CoBDC) with TiCT (the MXene phase) nanosheets via an interdiffusion reaction-assisted process. The resulting hybrid material was applied in the oxygen evolution reaction and achieved a current density of 10 mA cm at a potential of 1.64 V vs reversible hydrogen electrode and a Tafel slope of 48.2 mV dec in 0.1 M KOH. These results outperform those obtained by the standard IrO-based catalyst and are comparable with or even better than those achieved by the previously reported state-of-the-art transition-metal-based catalysts. While the CoBDC layer provided the highly porous structure and large active surface area, the electrically conductive and hydrophilic TiCT nanosheets enabled the rapid charge and ion transfer across the well-defined TiCT-CoBDC interface and facilitated the access of aqueous electrolyte to the catalytically active CoBDC surfaces. The hybrid nanosheets were further fabricated into an air cathode for a rechargeable zinc-air battery, which was successfully used to power a light-emitting diode. We believe that the in situ hybridization of MXenes and 2D MOFs with interface control will provide more opportunities for their use in energy-based applications.

a-d) Reproduced with permission. [61] Copyright 2017, Springer Nature. e) Possible OER routes on Zn 0.2 Co 0.8 O 2 with LOM mechanism. [59] Copyright 2019, Springer Nature. f) Scheme representing the proposed OER mechanism on the surface of La 2 LiIrO 6 in acid. Reproduced with permission. [66] Copyright 2016, Nature Publishing Group. g) The mechanism suggested for amorphous iridium oxide and leached perovskites with participation of activated oxygen in the reaction forming oxygen vacancies. Reproduced with permission. [51] Copyright 2018, Springer Nature.

Simultaneous realization of improved activity, enhanced stability, and reduced cost remains a desirable yet challenging goal in the search of electrocatalysis oxygen evolution reaction (OER) in acid. Herein, we report a novel strategy to prepare iridium single-atoms (Ir-SAs) on ultrathin NiCo2O4 porous nanosheets (Ir–NiCo2O4 NSs) by the co-electrodeposition method. The surface-exposed Ir-SAs couplings with oxygen vacancies (VO) exhibit boosting the catalysts OER activity and stability in acid media. They display superior OER performance with an ultralow overpotential of 240 mV at j = 10 mA cm–2 and long-term stability of 70 h in acid media. The TOFs of 1.13 and 6.70 s–1 at an overpotential of 300 and 370 mV also confirm their remarkable performance. Density functional theory (DFT) calculations reveal that the prominent OER performance arises from the surface electronic exchange-and-transfer activities contributed by atomic Ir incorporation on the intrinsic VO existed NiCo2O4 surface. The atomic Ir sites substantially elevate the electronic activity of surface lower coordinated Co sites nearby VO, which facilitate the surface electronic exchange-and-transfer capabilities. With this trend, the preferred H2O activation and stabilized *O have been reached toward competitively lower overpotential. This is a generalized key for optimally boosting OER performance.

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Neutral aqueous zinc−air batteries (ZABs) are an emerging type of energy devices with substantially elongated lifetime and improved recyclability compared to conventional alkaline ZABs. However, their development is impeded by the lack of robust bifunctional catalyst at the air-electrode for the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR). Here, we report the controlled synthesis of NiFe 2 O 4 /FeNi 2 S 4 heterostructured nanosheets (HNSs) that are highly efficient in catalyzing OER and ORR, therefore enabling neutral rechargeable ZABs. Associated with the formation of abundant oxide/ sulfide interfaces over NiFe 2 O 4 /FeNi 2 S 4 HNSs' surfaces, the catalyst's oxygen binding energy can be effectively tuned to enhance the OER and ORR activities, as revealed by the density functional theory calculations. In 0.2 M phosphate buffer solution, the optimized NiFe 2 O 4 /FeNi 2 S 4 HNSs present an excellent oxygen electrocatalytic activity and stability, with much lower OER and ORR overpotentials than single-component FeNi 2 S 4 or NiFe 2 O 4 and with negligible performance decay in accelerated durability testing. When used as an air-electrode, the NiFe 2 O 4 /FeNi 2 S 4 HNSs can deliver a power density of 44.4 mW cm −2 and a superior cycling stability (only 0.6% decay after 900 cycles at 0.5 mA cm −2 ), making the resultant ZAB the most efficient and robust one with a neutral aqueous electrolyte reported to date. This work highlights the essential function of the heterostructure interface in oxygen electrocatalysis, opening a new avenue to advanced neutral metal−air batteries.

Electrochemical water splitting to produce hydrogen and oxygen, as an important reaction for renewable energy storage, needs highly efficient and stable catalysts. Herein, FeS /CoS interface nanosheets (NSs) as efficient bifunctional electrocatalysts for overall water splitting are reported. The thickness and interface disordered structure with rich defects of FeS /CoS NSs are confirmed by atomic force microscopy and high-resolution transmission electron microscopy. Furthermore, extended X-ray absorption fine structure spectroscopy clarifies that FeS /CoS NSs with sulfur vacancies, which can further increase electrocatalytic performance. Benefiting from the interface nanosheets' structure with abundant defects, the FeS /CoS NSs show remarkable hydrogen evolution reaction (HER) performance with a low overpotential of 78.2 mV at 10 mA cm and a superior stability for 80 h in 1.0 m KOH, and an overpotential of 302 mV at 100 mA cm for the oxygen evolution reaction (OER). More importantly, the FeS /CoS NSs display excellent performance for overall water splitting with a voltage of 1.47 V to achieve current density of 10 mA cm and maintain the activity for at least 21 h. The present work highlights the importance of engineering interface nanosheets with rich defects based on transition metal dichalcogenides for boosting the HER and OER performance.

Zirconium acetylacetonate used as a co-precursor in the synthesis of CsPbI 3 quantum dots (QDs) increased their photoluminescence quantum efficiency to values over 90%. The top-emitting device structure on a Si substrate with high thermal conductivity (to better dissipate Joule heat generated at high current density) was designed to improve the light extraction efficiency making use of a strong microcavity resonance between the bottom and top electrodes. As a result of these improvements, light-emitting diodes (LEDs) utilizing Zr-modified CsPbI 3 QDs with an electroluminescence at 686 nm showed external quantum efficiency (EQE) of 13.7% at a current density of 108 mA cm −2 , which was combined with low efficiency roll-off (maintaining an EQE of 12.5% at a high current density of 500 mA cm −2 ) and a high luminance of 14 725 cd m −2 , and the stability of the devices being repeatedly lit (cycled on and off at high drive current density) has been greatly enhanced.