Hydrogen economy has emerged as a very promising alternative to the current hydrocarbon economy, which involves the process of harvesting renewable energy to split water into hydrogen and oxygen and ...then further utilization of clean hydrogen fuel. The production of hydrogen by water electrolysis is an essential prerequisite of the hydrogen economy with zero carbon emission. Among various water electrolysis technologies, alkaline water splitting has been commercialized for more than 100 years, representing the most mature and economic technology. Here, the historic development of water electrolysis is overviewed, and several critical electrochemical parameters are discussed. After that, advanced nonprecious metal electrocatalysts that emerged recently for negotiating the alkaline oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are discussed, including transition metal oxides, (oxy)hydroxides, chalcogenides, phosphides, and nitrides for the OER, as well as transition metal alloys, chalcogenides, phosphides, and carbides for the HER. In this section, particular attention is paid to the catalyst synthesis, activity and stability challenges, performance improvement, and industry‐relevant developments. Some recent works about scaled‐up catalyst synthesis, novel electrode designs, and alkaline seawater electrolysis are also spotlighted. Finally, an outlook on future challenges and opportunities for alkaline water splitting is offered, and potential future directions are speculated.
The hydrogen economy has emerged as a very promising alternative to the current hydrocarbon economy, which involves the process of harvesting renewable energy to split water into hydrogen and oxygen and then further utilization of hydrogen fuel. Alkaline water splitting represents the most mature and economic technology for clean hydrogen production, making high potential for successful implementation of hydrogen economy.
The electrocatalytic carbon dioxide reduction reaction (CO2RR) presents a sustainable route to convert renewable electricity to value-added fuels and feedstocks in the form of chemical energy. ...However, the selectivity and rate of conversion of CO2 to desirable carbon-based products, especially multicarbon products, remain below the requirement for its implementation at the commercial scale, which primarily originates from inadequate reactants and intermediates near catalytic surfaces during the CO2RR. The enrichment of reactants and intermediates provides one of the coping guidelines to improve CO2RR performance by accelerating the reaction rate and improving product selectivity. Herein, we discuss strategies to achieve the enrichment of reactants and intermediates through catalyst design, local microenvironment modulation, electrolyte regulation, and electrolyzer optimization. The structure and properties of CO2 are first presented, showing the necessity and feasibility of enriching reactants and intermediates. Next, the influence of the enrichment effect on CO2 electrolysis, i.e., accelerating the reaction rate and improving product selectivity, are comprehensively discussed. Then, catalyst design from micrometer scale to atom scale, including wettability and morphology regulation, surface modification, and tandem structure construction, as well as surface atom engineering, is highlighted to implement the enrichment of reactants and intermediates. Catalyst restructuring during the CO2RR process and its impact on the enrichment of intermediates and reactants are also discussed. Subsequently, enriching CO2 reactants and intermediates by modulating the local microenvironment to achieve high carbon utilization for the CO2RR to produce multicarbon products is reviewed. After that, insights into enriching reactants and intermediates through electrolyte regulation are provided by investigating various electrolytes, including aqueous solutions, organic solvents, and ionic liquids. Additionally, the key role of electrolyzer optimization in promoting the enrichment effect is considered. We end the review by outlining the remaining technological challenges and providing feasible suggestions aimed at directing the future employment of enrichment strategies to propel the practical implementation of CO2 electrolysis technology.
Transition‐metal phosphides have stimulated great interest as catalysts to drive the hydrogen evolution reaction (HER), but their use as bifunctional catalytic electrodes that enable efficient ...neutral‐pH water splitting has rarely been achieved. Herein, we report the synthesis of ternary Ni0.1Co0.9P porous nanosheets onto conductive carbon fiber paper that can efficiently and robustly catalyze both the HER and water oxidation in 1 m phosphate buffer (PBS; pH 7) electrolyte under ambient conditions. A water electrolysis cell comprising the Ni0.1Co0.9P electrodes demonstrates remarkable activity and stability for the electrochemical splitting of neutral‐pH water. We attribute this performance to the new ternary Ni0.1Co0.9P structure with porous surfaces and favorable electronic states resulting from the synergistic interplay between nickel and cobalt. Ternary metal phosphides hold promise as efficient and low‐cost catalysts for neutral‐pH water splitting devices.
Sheets and paper: Ternary Ni0.1Co0.9P porous nanosheets anchored onto conductive carbon fiber paper, can be used as a bifunctional catalytic material for driving both water reduction and oxidation reactions efficiently in neutral‐pH electrolyte under ambient conditions.
Layered molybdenum disulfide has demonstrated great promise as a low-cost alternative to platinum-based catalysts for electrochemical hydrogen production from water. Research effort on this material ...has focused mainly on synthesizing highly nanostructured molybdenum disulfide that allows the exposure of a large fraction of active edge sites. Here we report a promising microwave-assisted strategy for the synthesis of narrow molybdenum disulfide nanosheets with edge-terminated structure and a significantly expanded interlayer spacing, which exhibit striking kinetic metrics with onset potential of -103 mV, Tafel slope of 49 mV per decade and exchange current density of 9.62 × 10(-3) mA cm(-2), performing among the best of current molybdenum disulfide catalysts. Besides benefits from the edge-terminated structure, the expanded interlayer distance with modified electronic structure is also responsible for the observed catalytic improvement, which suggests a potential way to design newly advanced molybdenum disulfide catalysts through modulating the interlayer distance.
Heterogeneous supported metal nanoparticles (NPs) are extensively applied in a variety of chemical and energy conversion processes. Traditionally, these catalysts are prepared by deposition methods. ...However, they usually show wide ranging size distributions and are easily subject to poisoning and coarsening or agglomeration during the reactions. Alternatively, the time and cost-effective in situ exsolution strategy has successfully addressed the above drawbacks and is able to produce finer and more evenly distributed metal NPs even at relatively low metal loading. Endowed by their socketed nature, the exsolved metal NPs possess excellent operational stabilities as well as great catalytic activities. Moreover, these exsolved metal NPs are smart and can be regenerated upon redox treatments, further extending the lifetime of catalysts. This review presents a general idea in facilitating the degree of exsolution from various oxide substrates by summarizing the recent advances in the exsolution related studies and research outputs with a special emphasis on the understanding of the thermodynamical roles of different experimental parameters.
The anode oxygen evolution reaction (OER) is known to largely limit the efficiency of electrolyzers owing to its sluggish kinetics. While crystalline metal oxides are promising as OER catalysts, ...their amorphous phases also show high activities. Efforts to produce amorphous metal oxides have progressed slowly, and how an amorphous structure benefits the catalytic performances remains elusive. Now the first scalable synthesis of amorphous NiFeMo oxide (up to 515 g in one batch) is presented with homogeneous elemental distribution via a facile supersaturated co‐precipitation method. In contrast to its crystalline counterpart, amorphous NiFeMo oxide undergoes a faster surface self‐reconstruction process during OER, forming a metal oxy(hydroxide) active layer with rich oxygen vacancies, leading to superior OER activity (280 mV overpotential at 10 mA cm−2 in 0.1 m KOH). This opens up the potential of fast, facile, and scale‐up production of amorphous metal oxides for high‐performance OER catalysts.
Amorphous NiFeMo oxide (up to 515 g one batch) with homogeneous elemental distribution was synthesized through a facile supersaturated co‐precipitation method. The amorphous NiFeMo oxide undergoes rapid surface self‐reconstruction during OER that forms a metal oxy(hydroxide) active layer with oxygen vacancies, enabling efficient OER catalysis.
Late transition metal chalcogenide (LTMC) nanomaterials have been introduced as a promising Pt‐free oxygen reduction reaction (ORR) electrocatalysts because of their low cost, good ORR activity, high ...methanol tolerance, and facile synthesis. Herein, an overview on the design and synthesis of LTMC nanomaterials by solution‐based strategies is presented along with their ORR performances. Current solution‐based synthetic approaches towards LTMC nanomaterials include a hydrothermal/solvothermal approach, single‐source precursor approach, hot‐injection approach, template‐directed soft synthesis, and Kirkendall‐effect‐induced soft synthesis. Although the ORR activity and stability of LTMC nanomaterials are still far from what is needed for practical fuel‐cell applications, much enhanced electrocatalytic performance can be expected. Recent advances have emphasized that decorating the surface of the LTMC nanostructures with other functional nanoparticles can lead to much better ORR catalytic activity. It is believed that new synthesis approaches to LTMCs, modification techniques of LTMCs, and LTMCs with desirable morphology, size, composition, and structures are expected to be developed in the future to satisfy the requirements of commercial fuel cells.
Recent advances in the design and synthesis of late transition metal chalcogenides (LTMCs) by solution‐based approaches and their applications as Pt‐free oxygen reduction reaction (ORR) electrocatalysts are reviewed.
Ionic liquids (ILs) are new, innovative ionic solvents with rich physicochemical properties and intriguing pre‐organized solvent structures; these materials offer great potential to impact across ...versatile areas of scientific research, for example, synthetic inorganic chemistry. Recent use of ILs as precursors, templates, and solvents has led to inorganic materials with tailored sizes, dimensionalities, morphologies, and functionalities that are difficult to obtain, or even not accessible, by using conventional solvents. Poly(ionic liquid)s (PILs) polymerized from IL monomers also raise the prospect of modifying nucleation, growth, and crystallization of inorganic objects, shedding light on the synthesis of a wide range of new materials. Here we survey recent key progress in using ILs and PILs in the field of synthetic inorganic chemistry. As well as highlighting the unique features of ILs and PILs that enable advanced synthesis, the effects of adding other solvents to the final products, along with the emerging applications of the created inorganic materials will be discussed. We finally provide an outlook on several development opportunities that could lead to new advancements of this exciting research field.
Designer solvents and additives: Ionic liquids and poly(ionic liquid)s have demonstrated great potential as “designer solvents and additives” for advanced inorganic synthesis. This review surveys recent key progress in this exciting research field and speculates on possible future directions.
Abstract
Recently developed solid-state catalysts can mediate carbon dioxide (CO
2
) electroreduction to valuable products at high rates and selectivities. However, under commercially relevant ...current densities of > 200 milliamperes per square centimeter (mA cm
−2
), catalysts often undergo particle agglomeration, active-phase change, and/or element dissolution, making the long-term operational stability a considerable challenge. Here we report an indium sulfide catalyst that is stabilized by adding zinc in the structure and shows dramatically improved stability. The obtained ZnIn
2
S
4
catalyst can reduce CO
2
to formate with 99.3% Faradaic efficiency at 300 mA cm
−2
over 60 h of continuous operation without decay. By contrast, similarly synthesized indium sulfide without zinc participation deteriorates quickly under the same conditions. Combining experimental and theoretical studies, we unveil that the introduction of zinc largely enhances the covalency of In-S bonds, which “locks” sulfur—a catalytic site that can activate H
2
O to react with CO
2
, yielding HCOO* intermediates—from being dissolved during high-rate electrolysis.
The plating/stripping of Li dendrites can fracture the static solid electrolyte interphase (SEI) and cause significant dynamic volume variations in the Li anode, which give rise to poor cyclability ...and severe safety hazards. Herein, a tough polymer with a slide‐ring structure was designed as a self‐adaptive interfacial layer for Li anodes. The slide‐ring polymer with a dynamically crosslinked network moves freely while maintaining its toughness and fracture resistance, which allows it can to dissipate the tension induced by Li dendrites on the interphase layer. Moreover, the slide‐ring polymer is highly stretchable, elastic, and displays an ultrafast self‐healing ability, which allows even pulverized Li to remain coalesced without disintegrating upon consecutive cycling. The Li anodes demonstrate greatly improved suppression of Li dendrite formation, as evidenced by the high critical current density (6 mA cm−2) and stable cycling for the full cells with high‐areal capacity LiFePO4, high‐voltage NCM, and S cathodes.
A slide‐ring polymer with a high stiffness, high toughness and excellent fracture resistance is designed to adapt its shape to dynamic electrode volume variations and stabilize the lithium anode upon cycling.
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