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[Display omitted] • Hollow CoVO x /Ag heterojunction was synthesized for OER. • The interaction of CoVO x and Ag nanoparticles regulated the electronic structure. • The extrinsic catalytic activity of CoVO x /Ag is enhanced due to the hollow structure. • The OER overpotential for CoVO x /Ag-5 at 10 mA cm−2 is only 247 mV. • The catalyst can enable full water splitting with 100% Faraday efficiency. Developing high-active and inexpensive electrocatalysts for oxygen evolution reaction (OER) is very important in the field of water splitting. The catalytic performance of electrocatalysts can be significantly improved by optimizing the electronic structure and designing suitable nanostructure. In this work, we represent the synthesis of hollow CoVO x /Ag-5 for OER. Due to the interaction of CoVO x and Ag nanoparticles, the electronic structure is optimized to improve the intrinsic catalytic activity. Additionally, the extrinsic catalytic activity of CoVO x /Ag is enhanced by the abundant active sites from the hollow structure. As a result, the CoVO x /Ag-5 demonstrates significantly enhanced OER catalytic activity with a low overpotential of 247 mV at 10 mA cm−2. In addition, it also exhibits excellent durability, without obvious attenuation in performance after continuous operation for 60 h. Furthermore, the catalyst can enable full water splitting with appropriate 100 % Faraday efficiency, demonstrating its practical application. [ABSTRACT FROM AUTHOR]

Developing high‐efficiency bifunctional electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) to realize low‐cost water splitting is the premise for large‐scale production of hydrogen. The catalytic activity of an electrocatalysts greatly depends on its composition and structure. In this work, we report the preparation of hollow CoS2/MoS2 heterostructure using ZIF‐67 as the precursor. The ratio of Co and Mo are optimized to maximize the synergy of CoS2 and MoS2, due to their specific catalytic activity for OER and HER. The optimized CoS2/MoS2 exhibits good bifunctional catalytic activity in view of its low overpotentials for HER (170 mV) and OER (270 mV), as well as small cell voltage of 1.66 V for overall water splitting. This work provides a facile strategy to controllable fabrication of efficient bifunctional electrocatalysts for renewable energy applications. [ABSTRACT FROM AUTHOR]

Transition-metal chalcogenides especially MoS 2 are promising candidates as highly efficient electrocatalyst for hydrogen evolution reaction (HER). Nevertheless, the low conductivity and inert basal planes of MoS 2 limit its performance. In addition, the oxygen evolution reaction (OER) catalytic activity of MoS 2 is low. In this work, we report the synthesis of self-supported 1 T-MoS 2 /Co 3 S 4 /Ni 3 S 2 nanoarrays for overall water splitting. 1 T-MoS 2 can enhance electron transfer during the reaction process. Meanwhile, abundant interfaces and defects exist in the heterogeneous catalysts, which can bring more active sites and result in strong interaction among the different components. As a result, the 1 T-MoS 2 /Co 3 S 4 /Ni 3 S 2 nanoarray exhibits low overpotentials of 50 and 240 mV is achieved at 10 mA cm−2 for HER and OER with very high stability. In addition, it can catalyze overall water splitting with a low cell voltage of 1.55 V and 100% Faradic efficiency, demonstrating its practical applications. The present work offers a new route for developing 1 T-MoS 2 based hybrid electrocatalysts with desirable surface and interface structure for energy storage and conversion. [Display omitted] • Self-supported 1 T-MoS 2 /Co 3 S 4 /Ni 3 S 2 nanoarrays was developed for overall water splitting. • The abundant interfaces and defects in 1 T-MoS 2 /Co 3 S 4 /Ni 3 S 2 benefit its catalytic activity. • 1 T-MoS 2 can accelerate electron transfer during the catalytic process. • 1 T-MoS 2 /Co 3 S 4 /Ni 3 S 2 exhibits low HER and OER overpotentials of 50 and 240 mV. • 1 T-MoS 2 /Co 3 S 4 /Ni 3 S 2 can drive full water splitting at 1.55 V with 100% Faradic efficiency. [ABSTRACT FROM AUTHOR]

• Co-Co 6 Mo 6 C 2 @NC nano polyhedron was synthesized using ZIF-67 as a precursor. • The Co 6 Mo 6 C 2 can significantly improve the OER catalytic activity of the catalyst. • The Co-Co 6 Mo 6 C 2 @NC-5 exhibits a low OER overpotential of 270 mV at 10 mA cm−2. • The Co-Co 6 Mo 6 C 2 @NC-5 exhibits a high ORR half-wave potential of 0.80 V. • The Co-Co 6 Mo 6 C 2 @NC can be used as a bifunctional electrocatalyst for Zn-air battery. A high effective bifunctional electrocatalyst was developed for rechargeable Zn-air batteries by rational integrating high active Co sites for ORR and Co 6 Mo 6 C 2 specie for OER. [Display omitted] To facilitate the development of rechargeable metal-air batteries, the exploration of high effective bifunctional electrocatalysts is essential. In this work, we report a facile strategy to synthesize N doped carbon (NC) encapsulated Co-Co 6 Mo 6 C 2 (Co-Co 6 Mo 6 C 2 @NC) nano polyhedron using ZIF-67 as a precursor and investigated its catalytic performance for both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). The introduction of Co 6 Mo 6 C 2 into Co@NC can significantly improve the OER catalytic activity of the catalyst, while the high ORR catalytic activity of the catalyst is maintained. Specifically, Co-Co 6 Mo 6 C 2 @NC-5 shows a decent half-wave potential of 0.80 V for ORR, and a very low overpotential of 270 mV at 10 mA cm−2 for OER, demonstrating its bifunctional activity. The rechargeable Zn-air battery assembled using Co-Co 6 Mo 6 C 2 @NC-5 exhibits a maximum power density of 90.75 mW cm−2 and a high specific capacity of 768 mA h g−1, as well as good durability of 50 h without attenuation in performance, highlighting its practical application. [ABSTRACT FROM AUTHOR]

Abstract Oxygen evolution reaction (OER) plays a key role in electrochemical splitting of water and it is urgent to develop high-performance and cost-effective OER catalysts. In this work, we report the synthesis of V-Co/CoO@C nanorod as highly efficient OER catalysts. The V 2 O 5 nanowire and metal organic framework composite leads to the successful preparation of the catalyst. The V 2 O 5 nanowire not only induces the formation of Co/CoO species, but also facilitates uniform V doping. When used as OER catalyst, the V-Co/CoO@C nanorod only needs a low overpotential of 320 mV to achieve a high current density of 10 mA·cm−2. Graphical abstract Unlabelled Image Highlights • Porous V-Co/CoO@C nanorod was synthesized by using a V 2 O 5 @ZIF-67 as precursor. • The V-Co/CoO@C nanorod shows high OER activity of 10 mA·cm−2 at a η value of 320 mV. • The use of V 2 O 5 lead to the formation of Co/CoO and V doping. • The Co/CoO species and uniform V doping contributed to its OER performance. [ABSTRACT FROM AUTHOR]

• MoO 2 @MoS 2 @Co 9 S 8 heterostructure nanorod by utilizing MoO 3 @ZIF-67 as a precursor. • The nanorod is assembled by 2D nanosheet with high electrochemical surface area. • The nanorod can serve as bifunctional electrocatalyst for overall water splitting. • The HER and OER overpotentials at 10 mA cm−2 are 160 mV and 310 mV. • The high performance is induced by the synergistic effect of the heterostructure. Developing low-cost and high-efficiency bifunctional catalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) to catalyze electrochemical overall water splitting is critical for the production of hydrogen. Herein, we develop an in-situ reduction and vulcanization strategy to prepare MoO 2 @MoS 2 @Co 9 S 8 heterostructure nanorods by utilizing MoO 3 @ZIF-67 as a precursor. The reduction of MoO 3 can produce more conductive MoO 2 , and the vulcanization reaction can produce highly active MoS 2 for the HER as well as highly active Co 9 S 8 for the OER. In addition, the MoS 2 anchor on the MoO 2 not only facilitates electron transfer, but also interacts with Co 9 S 8 to induce a synergic catalytic effect by the electron transfer between them. Moreover, the 2D nanosheet assembled heterostructure nanorods can provide a large electrochemical surface area. Therefore, the merits of the materials are fully utilized and outstanding catalytic performances are achieved. MoO 2 @MoS 2 @Co 9 S 8 can catalyze HER and OER effectively with overpotentials of 160 and 310 mV at 10 mA cm−2, indicating its bifunctional activity. In addition, the two electrode electrolyzer catalyzed by MoO 2 @MoS 2 @Co 9 S 8 can reach 10 mA cm−2 current density at a cell voltage of 1.62 V with very high stability, demonstrating its practical application for water splitting. [ABSTRACT FROM AUTHOR]

Designing efficient oxygen evolution reaction (OER) electrocatalysts is crucial for practical applications in water splitting and metal-air battery devices. Special structures of materials often bring in unprecedented catalytic activity. Herein, we first report the synthesis of CoMoO 4 nanotube by using MoO 3 @ZIF-67 nanorod. The CoMoO 4 nanotube shows high OER activity with a low overpotential of 315 mV delivering a current density of 10 mA cm−2. The electro-catalytic activity surpasses that of many Co and Mo-based catalysts. Furthermore, the strategy presented here is facile, and can be extended to the synthesis of other Mo-based nanotube materials for energy storage and conversion. Unlabelled Image • CoMoO 4 nanotube was prepared by using MOF composite as precursor for the first time. • The CoMoO 4 shows high a specific surface area of 157 m2 g−1. • The CoMoO 4 shows high OER activity of 10 mA cm−2 at an overpotential of 315 mV. • The CoMoO 4 also shows outstanding long-term electrochemical durability. [ABSTRACT FROM AUTHOR]