Rational synthesis of hybrid, earth‐abundant materials with efficient electrocatalytic functionalities are critical for sustainable energy applications. Copper is theoretically proposed to exhibit ...high reduction capability close to Pt, but its high diffusion behavior at elevated fabrication temperatures limits its homogeneous incorporation with carbon. Here, a Cu, Co‐embedded nitrogen‐enriched mesoporous carbon framework (CuCo@NC) is developed using, a facile Cu‐confined thermal conversion strategy of zeolitic imidazolate frameworks (ZIF‐67) pre‐grown on Cu(OH)2 nanowires. Cu ions formed below 450 °C are homogeneously confined within the pores of ZIF‐67 to avoid self‐aggregation, while the existence of CuN bonds further increases the nitrogen content in carbon frameworks derived from ZIF‐67 at higher pyrolysis temperatures. This CuCo@NC electrocatalyst provides abundant active sites, high nitrogen doping, strong synergetic coupling, and improved mass transfer, thus significantly boosting electrocatalytic performances in oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). A high half‐wave potential (0.884 V vs reversible hydrogen potential, RHE) and a large diffusion‐limited current density are achieved for ORR, comparable to or exceeding the best reported earth‐abundant ORR electrocatalysts. In addition, a low overpotential (145 mV vs RHE) at 10 mA cm−2 is demonstrated for HER, further suggesting its great potential as an efficient electrocatalyst for sustainable energy applications.
A bi‐metallic (Cu and Co) embedded, N‐doped mesoporous carbon framework is developed as an oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) electrocatalyst, by a Cu‐confined thermal conversion strategy of Cu(OH)2 nanowires and ZIF‐67 polyhedrons. This hybrid electrocatalyst presents abundant bi‐metallic electrocatalytic active sites, high nitrogen doping level, strong synergetic coupling, and excellent mass transfer, thus significantly boosting electrocatalytic ORR and HER performances.
Hydrogen fuel acquisition based on electrochemical or photoelectrochemical water splitting represents one of the most promising means for the fast increase of global energy need, capable of offering ...a clean and sustainable energy resource with zero carbon footprints in the environment. The key to the success of this goal is the realization of robust earth‐abundant materials and cost‐effective reaction processes that can catalyze both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), with high efficiency and stability. In the past decade, one‐dimensional (1D) nanomaterials and nanostructures have been substantially investigated for their potential in serving as these electrocatalysts for reducing overpotentials and increasing catalytic activity, due to their high electrochemically active surface area, fast charge transport, efficient mass transport of reactant species, and effective release of gas produced. In this review, we summarize the recent progress in developing new 1D nanomaterials as catalysts for HER, OER, as well as bifunctional electrocatalysts for both half reactions. Different categories of earth‐abundant materials including metal‐based and metal‐free catalysts are introduced, with their representative results presented. The challenges and perspectives in this field are also discussed.
Exploring new electrocatalysts for water splitting is one main focus of clean hydrogen fuel conversion and utilization. This review summarizes the recent development of one‐dimensional earth‐abundant nanomaterials, including metal‐based or metal‐free materials, as catalysts for hydrogen evolution reaction, oxygen evolution reaction, and both. The rational design and preparation of novel electrocatalysts with structure and performance optimization will certainly suggest new opportunities of utilizing hydrogen fuel for global energy requirement.
Abstract
Electrochemical CO
2
reduction can produce valuable products with high energy densities but the process is plagued by poor selectivities and low yields. Propanol represents a challenging ...product to obtain due to the complicated C
3
forming mechanism that requires both stabilization of *C
2
intermediates and subsequent C
1
–C
2
coupling. Herein, density function theory calculations revealed that double sulfur vacancies formed on hexagonal copper sulfide can feature as efficient electrocatalytic centers for stabilizing both CO* and OCCO* dimer, and further CO–OCCO coupling to form C
3
species, which cannot be realized on CuS with single or no sulfur vacancies. The double sulfur vacancies were then experimentally synthesized by an electrochemical lithium tuning strategy, during which the density of sulfur vacancies was well-tuned by the charge/discharge cycle number. The double sulfur vacancy-rich CuS catalyst exhibited a Faradaic efficiency toward n-propanol of 15.4 ± 1% at −1.05 V versus reversible hydrogen electrode in H-cells, and a high partial current density of 9.9 mA cm
−2
at −0.85 V in flow-cells, comparable to the best reported electrochemical CO
2
reduction toward n-propanol. Our work suggests an attractive approach to create anion vacancy pairs as catalytic centers for multi-carbon-products.
Prussian blue (PB), the oldest synthetic coordination compound, is a classic and fascinating transition metal coordination material. Prussian blue is based on a three-dimensional (3-D) cubic ...polymeric porous network consisting of alternating ferric and ferrous ions, which provides facile assembly as well as precise interaction with active sites at functional interfaces. A fundamental understanding of the assembly mechanism of PB hetero-interfaces is essential to enable the full potential applications of PB crystals, including chemical sensing, catalysis, gas storage, drug delivery and electronic displays. Developing controlled assembly methods towards functionally integrated hetero-interfaces with adjustable sizes and morphology of PB crystals is necessary. A key point in the functional interface and device integration of PB nanocrystals is the fabrication of hetero-interfaces in a well-defined and oriented fashion on given substrates. This review will bring together these key aspects of the hetero-interfaces of PB nanocrystals, ranging from structure and properties, interfacial assembly strategies, to integrated hetero-structures for diverse sensing.
Several key aspects of the hetero-interfaces of Prussian blue (PB) nanocrystals, ranging from structure and properties, interfacial assembly strategies, to integrated hetero-structures for diverse sensing are introduced in this review.
The development of efficient hydrogen evolution reaction electrocatalysts is critical to the realization of clean hydrogen fuel production, while the sluggish kinetics of the Volmer‐step ...substantially restricts the catalyst performances in alkali electrolyzers, even for noble metal catalysts such as Pt. Here, a Pt‐decorated Ni3N nanosheet electrocatalyst is developed to achieve a top performance of hydrogen evolution in alkaline conditions. Possessing a high metallic conductivity and an atomic‐thin semiconducting hydroxide surface, the Ni3N nanosheets serve as not only an efficient electron pathway without the hindrance of Schottky barriers, but also provide abundant active sites for water dissociation and generation of hydrogen intermediates, which are further adsorbed on the Pt surface to recombine to H2. The Pt‐decorated Ni3N nanosheet catalyst exhibits a hydrogen evolution current density of 200 mA cm−2 at an overpotential of 160 mV versus reversible hydrogen electrode, a Tafel slope of ≈36.5 mV dec−1, and excellent stability of 82.5% current retention after 24 h of operation. Moreover, a hybrid cell consisting of a Pt‐decorated Ni3N nanosheet cathode and a Li‐metal anode is assembled to achieve simultaneous hydrogen evolution and electricity generation, exhibiting >60 h long‐term hydrogen evolution reaction stability and an output voltage ranging from 1.3 to 2.2 V.
A Pt‐decorated Ni3N nanosheet electrocatalyst with a top performance of hydrogen evolution in alkaline conditions is developed. The high metallic conductivity and an atomic‐thin Ni(OH)2 surface of Ni3N nanosheets provide an efficient electron pathway, and accelerate the water dissociation and generation of hydrogen intermediates. Moreover, an integrated hydrogen evolution and electricity generation cell based on the Ni3N/Pt electrocatalysts is also demonstrated.
Abstract
The electrochemical N
2
fixation to produce ammonia is attractive but significantly challenging with low yield and poor selectivity. Herein, we first used density function theory ...calculations to reveal adjacent bi-Ti
3+
pairs formed on anatase TiO
2
as the most active electrocatalytic centers for efficient N
2
lying-down chemisorption and activation. Then, by doping of anatase TiO
2
with Zr
4+
that has similar
d
-electron configuration and oxide structure but relatively larger ionic size, the adjacent bi-Ti
3+
sites were induced and enriched via a strained effect, which in turn enhanced the formation of oxygen vacancies. The Zr
4+
-doped anatase TiO
2
exhibited excellent electrocatalytic N
2
fixation performances, with an ammonia production rate (8.90 µg·h
−1
·cm
−2
) and a Faradaic efficiency of 17.3% at −0.45 V versus reversible hydrogen electrode under ambient aqueous conditions. Moreover, our work suggests a viewpoint to understand and apply the same-valance dopants in heterogeneous catalysis, which is generally useful but still poorly understood.
Fabrication of ultrathin 2D nonlayered nanomaterials remains challenging, yet significant due to the new promises in electrochemical functionalities. However, current strategies are largely ...restricted to intrinsically layered materials. Herein, a combinatorial self‐regulating acid etching and topotactic transformation strategy is developed to unprecedentedly prepare vertically stacked ultrathin 2D nonlayered nickel selenide nanosheets. Due to the inhibited hydrolyzation under acidic conditions, the self‐regulating acid etching results in ultrathin layered nickel hydroxides (two layers). The ultrathin structure allows limited epitaxial extension during selenization, i.e., the nondestructive topotactic transformation, enabling facile artificial engineering of hydroxide foundation frameworks into ultrathin nonlayered selenides. Consequently, the exquisite nonlayered nickel selenide affords high turnover frequencies, electrochemical surface areas, exchange current densities, and low Tafel slopes, as well as facilitating charge transfer toward both oxygen and hydrogen evolution reactions. Thus, the kinetically favorable bifunctional electrocatalyst delivers advanced and robust overall water splitting activities in alkaline intermediates. The integrated methodology may open up a new pathway for designing other highly active 2D nonlayered electrocatalysts.
Ultrathin 2D nonlayered NiSe nanosheets with a thickness of 1.25 nm are synthesized via a nondestructive topotactic selenization from their unconventional acid‐etched ultrathin layered Ni(OH)2 counterparts. The ultrathin character of the nanosheets is responsible for the intact selenization transformation, leading to advanced bifunctional oxygen evolution reaction and hydrogen evolution reaction catalytic activities in alkaline intermediates.
Abstract
Solar-driven electrochemical carbon dioxide (CO
2
) reduction is capable of producing value-added chemicals and represents a potential route to alleviate carbon footprint in the global ...environment. However, the ever-changing sunlight illumination presents a substantial impediment of maintaining high electrocatalytic efficiency and stability for practical applications. Inspired by green plant photosynthesis with separate light reaction and (dark) carbon fixation steps, herein, we developed a redox-medium-assisted system that proceeds water oxidation with a nickel-iron hydroxide electrode under light illumination and stores the reduction energy using a zinc/zincate redox, which can be controllably released to spontaneously reduce CO
2
into carbon monoxide (CO) with a gold nanocatalyst in dark condition. This redox-medium-assisted system enables a record-high solar-to-CO photoconversion efficiency of 15.6% under 1-sun intensity, and an outstanding electric energy efficiency of 63%. Furthermore, it allows a unique tuning capability of the solar-to-CO efficiency and selectivity by the current density applied during the carbon fixation.
The capability of electrocatalytic reduction of carbon dioxide (CO
2
) using nitrogen (N)-doped carbon strongly depends on the N-doping level and their types. In this work, we developed a strategy to ...generate mesoporous N-doped carbon frameworks with tunable configurations and contents of N dopants, by using a secondary doping process via the treatment of N,N-dimethylformamide (DMF) solvent. The obtained mesoporous N-doped carbon (denoted as MNC-D) served as an efficient electrocatalyst for electroreduction of CO
2
to CO. A high Faradaic efficiency of ∼ 92% and a partial current density for CO of −6.8 mA·cm
−2
were achieved at a potential of −0.58 V vs. RHE. Electrochemical analyses further revealed that the active sites within the N-doped carbon catalysts were the pyridinic N and defects generated by the DMF treatment, which enhanced the activation and adsorption CO
2
molecules. Our study suggests a new approach to develop efficient carbon-based catalysts for potential scalable CO
2
RR to fuels and chemicals.
We report a facile, two-step hydrothermal synthesis of a novel Co304/a-Fe2O3 branched nanowire heterostructure, which can serve as a good candidate for lithium-ion battery anodes with high Li＋ ...storage capacity and stability. The single-crystalline, primary C0304 nanowire trunk arrays directly grown on Ti substrates allow for efficient electrical and ionic transport. The secondary a-Fe2O3 branches provide enhanced surface area and high theoretical Li＋ storage capacity, and can also serve as volume spacers between neighboring Co3O4 NW arrays to maintain electrolyte penetration as well as reduce the aggregation during Li＋ intercalation, thus leading to improved electrochemical energy storage performance.
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