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The oxygen evolution reaction (OER) is an important half-reaction in rechargeable metal–air batteries and water splitting devices, and it suffers from slow kinetics due to the multiple step proton-electron coupled process. Therefore, the major challenge for the OER is to develop durable and low-cost electrocatalysts with high catalytic performance. Herein, a ternary metal CoNiFe subacetate nano prism (CoNiFe NP) was synthesized by a one-step hydrothermal method, with the aim of accelerating the water dissociation and improving the reaction rate using the synergy of the ternary metal. The results show that the electrocatalytic performance of the ternary metal CoNiFe layered double hydroxide is significantly improved compared with the binary metal and single metal catalysts. In particular, the overpotential of the prepared CoNiFe NP for the OER at 10 mA cm−2 is as low as 292 mV, and the Tafel slope is 75.6 mV dec−1. This work provides a new platform for the design of medium-entropy electrocatalysts using the interaction of polymetallic components. [ABSTRACT FROM AUTHOR]

Nano bowl-like Co–Co6Mo6C2 coated by N,P co-doped carbon (Co–Co6Mo6C2@NPC) is reported as an electrocatalyst for Zn–air batteries. Co–Co6Mo6C2@NPC only needs an overpotential of 210 mV at 10 mA cm−2 for the OER, and the half-wave potential for the ORR is 0.81 V. In addition, the Co–Co6Mo6C2@NPC based battery shows a large open-circuit voltage of 1.335 V and a maximum power density of 160.5 mW cm−2, as well as good stability. The improved catalytic performance can be ascribed to the co-existence of Co6Mo6C2 and Co species to improve the intrinsic catalytic activity, and the bowl-like nanostructure to facilitate the mass transfer. [ABSTRACT FROM AUTHOR]

The development of a green and sustainable process for electrochemical ammonia synthesis has a significant impact on modern society in terms of agricultural and industrial development, as well as energy reform. The electrocatalytic nitrogen reduction reaction (NRR) has been regarded as a promising strategy and the efficiency of the NRR strongly depends on electrocatalysts with excellent activity, selectivity, and stability. Metal sulfides have been regarded as potential electrocatalysts due to the "accept and back-donate" interaction of metals with N2. In addition, it has been proposed that both the intrinsic and extrinsic catalytic activity, selectivity and stability of metal sulfides can be improved through defect and interface engineering. In this review, the recent progress on metal sulfides toward the NRR is summarized based on defect and interface engineering. The typical synthetic methods, physicochemical properties, and catalytic performances of the catalysts are outlined to provide insights into the structure–performance relationship of the catalysts. In particular, the origin of the outstanding NRR catalytic activity, selectivity and stability was revealed from both experimental and theoretical perspectives. Furthermore, the remaining challenges and future perspectives are presented with the aim of providing insightful guidance for developing more efficient NRR electrocatalysts. [ABSTRACT FROM AUTHOR]

The large-scale application of clean electrochemical energy storage and conversion systems such as water-splitting devices and Zn–air batteries greatly depends on the development of low-cost and highly efficient electrocatalysts. Transitional metal sulfides (TMSs) have gained great research interest owing to their high intrinsic catalytic activity, adjustable electronic structures, and various crystal structures and phases. Meanwhile, metal–organic frameworks (MOFs) are ideal precursors for the preparation of TMSs due to the diverse metal nodes, organic ligands, topologies, and morphologies of MOFs. In addition, MOFs could act as hosts for the incorporation of guest molecules, which could further expand the metal types of TMSs. In this review, the recent progress of MOF-derived TMS electrocatalysts for hydrogen evolution reactions (HERs), oxygen evolution reactions (OERs) and oxygen reduction reactions (ORRs) are summarized. After a brief introduction to the reaction mechanisms, the preparation strategies, structures, catalytic performances, and catalytic mechanisms of the TMSs are discussed to give readers a comprehensive understanding of this prosperous field. The strategies such as nanostructure engineering, interface engineering and heteroatom doping used to improve the performance of the electrocatalysts are discussed in each section. In addition, bifunctional catalytic performances of the catalysts for overall water splitting and rechargeable Zn–air batteries are illustrated. Furthermore, challenges and opportunities for the future development of this field are proposed. We expect this review could provide guidelines for the design and fabrication of TMSs, and initiate more efforts and new discoveries in this emerging research area. [ABSTRACT FROM AUTHOR]

Benefiting from the high electrochemical surface area brought by the 2D nanosheet structure, MoS2 has received great research attention for the hydrogen evolution reaction (HER). Recently, it has been demonstrated that by constructing a transitional metal sulfide–MoS2 heterostructure, the HER performance of the MoS2-based catalysts can be further improved. It is even possible to obtain bifunctional catalysts for both HER and oxygen evolution reaction (OER) due to the synergistic effect of the different components in the composite, the electronic effect to enable an efficient electron transfer and appropriate binding energy for the intermediates of the electrocatalytic reactions, and the surface defects on the interface of the heterostructures. Herein, we review the recent progress on the construction of the transitional metal sulfide–MoS2 heterostructure for water splitting based on non-self-supporting and self-supporting catalysts. The surface and interface parameters of the heterostructures are discussed in detail to reveal the key roles of the hybrid structures for energy conversion. We also pay special attention to the theoretical simulations based on first principles to clarify the relationships between the electrochemical performance and structure parameters. Finally, the prospects and challenges of the transition metal sulfide–MoS2 heterostructures for water splitting in the future are proposed to prompt the reasonable design of transition metal sulfide–MoS2 heterostructures for full water splitting. [ABSTRACT FROM AUTHOR]

Boron-containing cobalt (Co–B) nanoparticles (NPs) synthesized by the borohydride reduction process were subjected to ammonization. Part of B species segregate onto particle surfaces to form ultrathin h-BN shells which stabilize highly dispersed Co NPs under harsh conditions and the remaining B atoms interact strongly with Co atoms inside the NPs. The formed CoBx@h-BN core–shell nanocatalysts exhibit an overpotential of 290 mV at a current density of 10 mA cm−2 making them among the most active catalysts for the oxygen evolution reaction (OER) and they present 150 h OER stability. The improved OER performance has been attributed to the synergetic role of the confinement effect of h-BN shells and activation effect of subsurface B atoms. This work suggests a simple synthetic route to prepare highly active and stable metal nanocatalysts without using any surfactants and supports. [ABSTRACT FROM AUTHOR]

CO2 capture via solid adsorption technology relies on the development of low-cost and high-performance new solid adsorbents. The robust and large-scale produced hexagonal boron nitride (h-BN) porous materials are an ideal candidate but present low CO2 adsorption properties. Here, we report that in situ carbon doping of BN materials (BCN) can be facilely controlled by thermal annealing of boric acid and melamine mixtures in various atmospheres. CO2 uptake of the BCN materials is in the range of 3.74–3.91 mmol CO2 g−1 (165–172 mg CO2 g−1) at 298 K and ambient pressure, whereas it is only 1.16–1.66 mmol CO2 g−1 (53.0–73.1 mg CO2 g−1) over the pure BN materials. The separation coefficient between CO2 and N2 is up to 74 and no decrease in the adsorption performance was observed after nine adsorption/desorption cycles. The BCN material presents the best performance among known BN-based sorbents, which is comparable to many excellent carbon materials. Detailed characterization reveals that the incorporation of carbon into the BN matrix increases the density of ultramicropores (＜0.7 nm) and chemical defects, consequently enhancing the CO2 adsorption capacity and the selectivity over N2 molecules. [ABSTRACT FROM AUTHOR]

Nano bowl-like Co-Co 6 Mo 6 C 2 coated by N,P co-doped carbon (Co-Co 6 Mo 6 C 2 @NPC) is reported as an electrocatalyst for Zn-air batteries. Co-Co 6 Mo 6 C 2 @NPC only needs an overpotential of 210 mV at 10 mA cm -2 for the OER, and the half-wave potential for the ORR is 0.81 V. In addition, the Co-Co 6 Mo 6 C 2 @NPC based battery shows a large open-circuit voltage of 1.335 V and a maximum power density of 160.5 mW cm -2 , as well as good stability. The improved catalytic performance can be ascribed to the co-existence of Co 6 Mo 6 C 2 and Co species to improve the intrinsic catalytic activity, and the bowl-like nanostructure to facilitate the mass transfer.