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Hydrogen energy could be a economic and powerful technology for sustainable future. Producing hydrogen fuel by electrochemical water splitting has attracted intense interest. Due to their physical and chemical properties, two-dimensional (2D) nanomaterials have sparked immense interest in water electrocatalysis for hydrogen production. This review focuses on the emerging nanocatalysts in 2D nanoarchitectures for electrocatalytic hydrogen production. The fundamentals of HER are firstly depicted, following the discussion of recent advances in typical 2D electrocatalysts for HER. The insights into the relationship among the synthetic protocols, structure, catalytic performance and thermodynamics will be discussed in details. Finally, the outlooks regarding further development of 2D nanocatalysts for HER are proposed. We hope this review will offer a comprehensive understanding in 2D nanocatalysts to promote electrochemical hydrogen production.

This work reports an efficient NiS

The efficiency of electrochemical water splitting is severely restricted by the slow oxygen evolution reaction (OER) on the anode. Therefore, the design and synthesis of high-performance electrocatalysts for anodic oxygen evolution is crucial for the industrialization of hydrogen production by electrolysis of water. Herein, an efficient core-shell Ni(OH)2@NiFe LDH electrocatalyst was designed with the assistant of ionic liquid for OER. The ionic liquid delayed the crystallization ability of Ni2+ ions and then facilitated the formation of NiFe LDH coated Ni(OH)2 structure. The as-obtained core-shell Ni(OH)2@NiFe LDH exhibited outstanding OER electrocatalytic activity that only required overpotentials of 258 mV to deliver current densities of 100 mA cm-2, and a decent stability of at least 300 h under a large current density of 100 mA cm-2. This study provides a valuable reference for the structure design of NiFe LDH based catalyst.

Developing efficient platinum (Pt)-based electrocatalysts is enormously significant for fuel cells. Herein, we report an integrated electrocatalyst of ultralow-Pt alloy encapsulated into nitrogen-doped nanocarbon architecture for efficient oxygen reduction reaction. This hybrid Pt-based catalyst achieves a mass activity of 3.46 A mgpt−1 at the potential of 0.9 V vs. RHE with a negligible stability decay after 10,000 cycles. More importantly, this half-cell activity can be expressed at full cell level with a high Pt utilization of 10.22 W mgPt−1cathode and remarkable durability after 30,000 cycles in single-cell. Experimental and theoretical investigations reveal that a highly strained Pt structure with an optimal Pt-O binding energy is induced by the incorporation of Co/Ni into Pt lattice, which would account for the improved reaction kinetics. The synergistic catalysis due to nitrogen-doped nanocarbon architecture and active Pt component is responsible for the enhanced catalytic activity. Meanwhile, the strong metal-support interaction and optimized hydrophilic properties of nanocarbon matrix facilitate efficient mass transport and water management. This work may provide significant insights in designing the low-Pt integrated electrocatalysts for fuel cells and beyond.

Developing bifunctional catalysts for oxygen electrochemical reactions is essential for high-performance electrochemical energy devices. Here, a Mott-Schottky heterojunction composed of porous cobalt-nitrogen-carbon (Co-N-C) polyhedra containing abundant metal-phosphides for reversible oxygen electrocatalysis is reported. As a demonstration, this catalyst shows excellent activity in the oxygen electrocatalysis and thus delivers outstanding performance in rechargeable zinc-air batteries (ZABs). The built-in electric field in the Mott-Schottky heterojunction can promote electron transfer in oxygen electrocatalysis. More importantly, an appropriate d-band center of the heterojunction catalyst also endows oxygen intermediates with a balanced adsorption/desorption capability, thus enhancing oxygen electrocatalysis and consequently improving the performance of ZABs. The work demonstrates an important design principle for preparing efficient multifunctional catalysts in energy conversion technologies.

Driven by the energy crisis and environmental pollution, developing sustainable clean energy is an effective strategy to realize carbon neutrality. Electrocatalytic reactions are crucial to sustainable energy conversion and storage technologies, and advanced electrocatalysts are required to improve the sluggish electrocatalytic reactions. The magnetic field, as a thermodynamic parameter independent of temperature and pressure, is vital in the construction of electrocatalysts and enhancement of electrocatalysis. In this Review, the recent progress of magnetic field-assisted construction of electrocatalysts and enhancement of electrocatalysis is comprehensively summarized. Originating from the structure-activity-performance relationship of electrocatalysts, the fundamentals of the magnetic field-induced construction of electrocatalysts, including the magnetocaloric effect, nucleation and growth, and phase regulation, have been illustrated. In addition, the magnetic effect on the electrocatalytic reaction, namely, the magnetothermal, magnetohydrodynamic and micro magnetohydrodynamic, Maxwell stress, Kelvin force, and spin selection effects, are discussed. Finally, the perspective and challenges for magnetic field-assisted construction of electrocatalysts and enhancement of electrocatalysis are proposed.

Bimetallic sulfides are expected to realize efficient CO2 electroreduction into formate over a wide potential window, however, will undergo in situ structural evolution under the reaction conditions. Therefore, clarifying the structural evolution process, the real active site and the catalytic mechanism appear significance. Here, taking Cu2SnS3 as an example, we unveiled that Cu2SnS3 occurred self-adapted phase separation toward forming the stable SnO2@CuS and SnO2@Cu2O heterojunction during the electrochemical process. Theoretical calculations illustrated that the strongly coupled interfaces as real active sites driven the electron self-flow from Sn4+ to Cu+, thereby promoting the delocalized Sn sites to combine HCOO* with H*. Cu2SnS3 nanosheets achieve over 83.4% formate selectivity in a wide potential range from -0.6 V to -1.1 V. Our findings provide insight into the structural evolution process and performance-enhanced origin of ternary sulfides under the CO2 electroreduction.

Cu-based electrocatalysts with favorable facets and Cu+ can boost CO2 reduction to valuable multi-carbon products. However, the inevitable Cu+ reduction and phase evolution usually result in poor performance. Herein, we fabricate CuI nanodots with favorable (220) facets and stable Cu+ state, accomplished by operando reconstruction of Cu(OH)2 under CO2- and I--contained electrolyte for enhanced CO2-to-C2H4 conversion. In-situ Raman spectroscopy and thermodynamic potential analysis reveal the preferred formation of CuI which is stabilized by I-; vacuum gas electroresponse experiments and density functional theory (DFT) calculations demonstrate that CO2-related species induce the exposure of (220) of CuI. The resulting electrocatalysts exhibit a high C2H4 Faradaic efficiency of 72.4% at a large current density of 800 mA cm-2 and robust stability for 12 h in a flow cell. Combined in-situ ATR-SEIRS spectroscopic characterizations and DFT calculations indicate the (220) facets and stable Cu+ in CuI synergistically facilitate CO2/*CO adsorption and *CO dimerization.

We report an amino-functionalized indium-organic framework for efficient CO2 reduction to formate. The immobilized amino groups strengthen the absorption and activation of CO2 and stabilize the active intermediates, which endow an enhanced catalytic conversion to formate despite the inevitable reduction and reconstruction of the functionalized indium-based catalyst during electrocatalysis. The reconstructed amino-functionalized indium-based catalyst demonstrates a high Faradaic efficiency of 94.4 % and a partial current density of 108 mA cm-2 at -1.1 V vs. RHE in a liquid-phase flow cell, and also delivers an enhanced current density of ca. 800 mA cm-2 at 3.4 V for the formate production in a gas-phase flow cell configuration. This work not only provides a molecular functionalization and assembling concept of hybrid electrocatalysts but also offers valuable understandings in electrocatalyst evolution and reactor optimization for CO2 electrocatalysis and beyond.

Hydrazine fuel cells are promising sustainable power sources. However, the high price and limited reserves of noble metal catalysts that promote the sluggish cathodic and anodic electrochemical reactions hinder their practical applications. Reflecting the enhanced diffusion and improved kinetics of nanostructured non-noble metal electrocatalysts, we report an efficient zeolitic-imidazole framework-derived trifunctional electrocatalyst for hydrazine oxidation, oxygen, and hydrogen peroxide reduction. Experimental results and theoretical calculations corroborate that the nanocarbon architecture with abundant Co-N species enhances the electronic interaction and optimizes the energy barriers of anodic hydrazine oxidation and cathodic oxygen reduction. The resulting assembled hydrazine-oxygen fuel cell yields a cell voltage and power density of 0.74 V and 20.5 mW cm-2, respectively. Moreover, benefiting from the liquid-liquid diffusion, the hydrazine-hydrogen peroxide cell shows a boosted cell voltage and power density, corresponding to 1.68 V and 41.0 mW cm-2. This work offers a highly active non-noble metal multifunctional electrocatalyst with a pioneering diffusion philosophy in the liquid electrochemical cells.

Lithium-ion batteries revolutionize portable electronics and enable vehicle electrification. However, the excessive binders and additives are often involved in their fabrications with delicate yet complicated assembly procedures. This work reports a universal layer-by-layer assembly method to prepare the integrated electrodes by continuous carbon nanotube socks and active materials. Carbon nanotubes are not only the excellent conductive networks and the current collector but also the effective binder materials to efficiently net the active materials. The pouch cell assembled by the integrated hybrid electrodes shows a high specific capacity (141 mA h g−1 on the Li4Ti5O12 cathode), remarkable rate capability (135.2 mA h g−1 at 10 C), adequate safety, and flexibility. This work provides a facile approach for fabricating integrated electrodes, which holds great potential in advancing future design and assembly of hybrid materials for energy storage technologies.

Highlights This review summarizes the recent progress and application of different metal-organic frameworks (MOFs)-derived non-noble metal materials for zinc-air batteries in the past few years. This work gives extensive insights in understanding the relationship between design strategies and structure-activity relationship. The challenges and prospects of MOF-derived oxygen electrocatalysts for zinc-air batteries are proposed., Oxygen electrocatalysts are of great importance for the air electrode in zinc-air batteries (ZABs). Owing to the high specific surface area, controllable pore size and unsaturated metal active sites, metal–organic frameworks (MOFs) derivatives have been widely studied as oxygen electrocatalysts in ZABs. To date, many strategies have been developed to generate efficient oxygen electrocatalysts from MOFs for improving the performance of ZABs. In this review, the latest progress of the MOF-derived non-noble metal–oxygen electrocatalysts in ZABs is reviewed. The performance of these MOF-derived catalysts toward oxygen reduction, and oxygen evolution reactions is discussed based on the categories of metal-free carbon materials, single-atom catalysts, metal cluster/carbon composites and metal compound/carbon composites. Moreover, we provide a comprehensive overview on the design strategies of various MOF-derived non-noble metal–oxygen electrocatalysts and their structure-performance relationship. Finally, the challenges and perspectives are provided for further advancing the MOF-derived oxygen electrocatalysts in ZABs.

As a key component of batteries, the electrolyte determines the ion transport and interface chemistry of the cathode and anode. In this work, we develop a dual-network structured hydrogel electrolyte composed of polyacrylamide (PAM), sodium alginate (SA) and potassium iodide (KI) for solid-state zinc-air/iodide hybrid batteries. The assembled hybrid battery shows excellent renewability and a long cycling life of 110 h with a high energy efficiency of 80 %. The ion-crosslinked dual-network structure endows the material with improved mechanical strength and increased ionic conductivity. More importantly, the introduction of iodine species not only offers more favorable cathodic kinetics of iodide/iodate redox than oxygen electrocatalysis but also regulates the solvation structure of zinc ions to ensure better interface stability. This work provides significant concepts for developing novel solid-state electrolytes to realize high-performance energy devices and technologies.

Developing robust oxygen electrocatalyst with high-performance is very significant for practical rechargeable Zn-air battery. We report herein the preparation of three-dimensional continuous nanocarbon network composed of interconnected nitrogen-doped carbon nanotubes and its application as oxygen electrocatalysis in rechargeable Zn-air battery. Except the excellent electrochemical bifunctionality, this carbon nanotube matrix also delivers an impressive battery performance. Specifically, an open-circuit voltage of 1.50 V as well as a high power density of 220 mW cm−2 with remarkable cycling stability for 1600 h is achieved in the rechargeable Zn-air battery. The study not only provides an efficient bifunctional oxygen electrocatalyst but more importantly may pave significant concepts in designing robust electrode for long-life rechargeable Zn-air battery and other energy technologies.

Designing earth-abundant electrocatalysts with high performance towards water oxidation is highly decisive for the sustainable energy technologies. This study develops a facile natural corrosion approach to fabricate nickel-iron hydroxides for water oxidation. The resulted electrode demonstrates an outstanding activity and stability with an overpotential of 275 mV to deliver 10 mA·cm−2. Experimental and theoretical results suggest the corrosion-induced formation of hydroxides and their transformation to oxyhydroxides would account for this excellent performance. This work not only provides an interesting corrosion approach for the fabrication of excellent water oxidation electrode, but also bridges traditional corrosion engineering and novel materials fabrication, which would offer some insights in the innovative principles for nanomaterials and energy technologies.

Electroreduction of carbon dioxide (CO2) is attractive for efficiently recycling excessive CO2 to value-added feedstocks. However, their efficiency and selectivity strongly rely on the electrocatal...

Electrocatalytic conversion of carbon dioxide (CO2 ) is promising for balancing carbon cycles while producing value-added feedstocks. Herein, ultrathin ZnIn2 S4 nanosheets with abundant Zn vacancies are demonstrated for electrochemically reducing CO2 to formate. Specifically, a partial current density of 245 mA cm-2 with a near-unity faradaic efficiency of 94 % for formate generation was achieved over the ultrathin ZnIn2 S4 nanosheets in a flow cell configuration. Experimental and theoretical results revealed that abundant Zn vacancies in the ultrathin ZnIn2 S4 nanosheets with a high electrochemically active surface area synergistically optimized the intermediate binding energy and contributed to the boosted selectivity and activity. This work may provide useful understandings in designing efficient catalysts for selective CO2 electroreduction.