The crystalline‐amorphous (c–a) heterostructure is verified as a promising design for oxygen evolution reaction (OER) catalysts due to the concerted advantages of the crystalline and amorphous phase. ...However, most heterostructures via asynchronous heterophase synthesis suffer from the limited synergistic effect because of the sparse c–a interfaces. Here, a highly efficient and stable OER electrocatalyst with dense c–a interfacial sites is reported by hybridizing crystalline Ag and amorphous NiCoMo oxides (NCMO) on the nickel foam (NF) via synchronous dual‐phase synthetic strategy. In 1 m KOH, the as‐obtained Ag/NCMO/NF catalyst exhibits a low OER overpotential of 243 mV to attain 10 mA cm−2 and a small Tafel slope of 67 mV dec−1. Theoretical calculations indicate that the c–a interface can efficiently modulate the electronic structure of the interfacial sites and lower the OER overpotential. Besides, in situ Raman spectroscopy results demonstrate that the c–a interfacial sites can promote the irreversible phase transition to the metal oxy(hydroxide) active phase, and the dense c–a interfaces can stabilize the active phase during the whole OER process.
Synchronous crystalline–amorphous (c–a) phase synthetic strategy is used to obtain Ag and NiCoMo oxide (NCMO) heterostructure with dense c–a interfacial sites. The resultant Ag/NCMO electrocatalysts exhibit enhanced oxygen evolution activity than the asynchronously synthesized sample with sparse interfacial sites.
Sodium metal anodes are poor due to the reversibility of Na plating/stripping, which hinders their practical applications. A strategy to form a sodiophilic Au–Na alloy interphase on a Cu current ...collector, involving a sputtered Au thin layer, is shown to enable efficient Na plating/stripping for a certain period of time. Herein, electrochemical behaviors of Na plating on different substrates are explored, and it is revealed that the sodiophilic interphase can be achieved universally by in situ formation of M–Na (M = Au, Sn, and Sb) alloys during Na plating prior to Na bulk deposition in the initial cycle. Moreover, it is found that repetitive alloying–dealloying leads to falling‐off of thin film sodiophilic materials and thus limits the lifespan of efficient Na cycling. Therefore, an approach is further developed by employing particles of sodiophilic materials combined with the control over the cutoff potential, which significantly improves the stability of Na plating/stripping process. Especially, the low‐cost Cu@Sn‐NPs and Cu@Sb‐MPs composite current collectors allow Na plating and stripping to cycle for 2000 and 1700 times with the average efficiency of 99.9% at 2 mA cm−2.
Stable Na plating/stripping electrochemical behaviors are achieved by using the in situ formed sodiophilic sodium‐metal (metal = Au, Sn, Sb) alloy interphase. By simultaneous control over the stripping cut‐off potential and employment of anchored metal particles, Na plating/stripping cycling is extended to 2000 times at 2 mA cm−2 with an average Coulombic efficiency of 99.9% on the sodium‐metal alloy‐based interphase.
Dendrite growth of alkali metal anodes limited their lifetime for charge/discharge cycling. Here, we report near-perfect anodes of lithium, sodium, and potassium metals achieved by electrochemical ...polishing, which removes microscopic defects and creates ultra-smooth ultra-thin solid-electrolyte interphase layers at metal surfaces for providing a homogeneous environment. Precise characterizations by AFM force probing with corroborative in-depth XPS profile analysis reveal that the ultra-smooth ultra-thin solid-electrolyte interphase can be designed to have alternating inorganic-rich and organic-rich/mixed multi-layered structure, which offers mechanical property of coupled rigidity and elasticity. The polished metal anodes exhibit significantly enhanced cycling stability, specifically the lithium anodes can cycle for over 200 times at a real current density of 2 mA cm
with 100% depth of discharge. Our work illustrates that an ultra-smooth ultra-thin solid-electrolyte interphase may be robust enough to suppress dendrite growth and thus serve as an initial layer for further improved protection of alkali metal anodes.
Facile interconversion between CO2 and formate/formic acid (FA) is of broad interest in energy storage and conversion and neutral carbon emission. Historically, electrochemical CO2 reduction reaction ...to formate on Pd surfaces was limited to a narrow potential range positive of −0.25 V (vs RHE). Herein, a boron-doped Pd catalyst (Pd–B/C), with a high CO tolerance to facilitate dehydrogenation of FA/formate to CO2, is initially explored for electrochemical CO2 reduction over the potential range of −0.2 V to −1.0 V (vs RHE), with reference to Pd/C. The experimental results demonstrate that the faradaic efficiency for formate (ηHCOO– ) reaches ca. 70% over 2 h of electrolysis in CO2-saturated 0.1 M KHCO3 at −0.5 V (vs RHE) on Pd–B/C, that is ca. 12 times as high as that on homemade or commercial Pd/C, leading to a formate concentration of ca. 234 mM mg–1 Pd, or ca. 18 times as high as that on Pd/C, without optimization of the catalyst layer and the electrolyte. Furthermore, the competitive selectivity ηHCOO–/ηCO on Pd–B/C is always significantly higher than that on Pd/C despite a decreases of ηHCOO– and an increases of the CO faradaic efficiency (ηCO) at potentials negative of −0.5 V. The density functional theory (DFT) calculations on energetic aspects of CO2 reduction reaction on modeled Pd(111) surfaces with and without H-adsorbate reveal that the B-doping in the Pd subsurface favors the formation of the adsorbed HCOO*, an intermediate for the FA pathway, more than that of *COOH, an intermediate for the CO pathway. The present study confers Pd–B/C a unique dual functional catalyst for the HCOOH ↔ CO2 interconversion.
Abstract
Electrocatalytic reduction of CO
2
to fuels and chemicals is one of the most attractive routes for CO
2
utilization. Current catalysts suffer from low faradaic efficiency of a CO
2
...-reduction product at high current density (or reaction rate). Here, we report that a sulfur-doped indium catalyst exhibits high faradaic efficiency of formate (>85%) in a broad range of current density (25–100 mA cm
−2
) for electrocatalytic CO
2
reduction in aqueous media. The formation rate of formate reaches 1449 μmol h
−1
cm
−2
with 93% faradaic efficiency, the highest value reported to date. Our studies suggest that sulfur accelerates CO
2
reduction by a unique mechanism. Sulfur enhances the activation of water, forming hydrogen species that can readily react with CO
2
to produce formate. The promoting effect of chalcogen modifiers can be extended to other metal catalysts. This work offers a simple and useful strategy for designing both active and selective electrocatalysts for CO
2
reduction.
Surface plasmon resonances (SPRs) have been found to promote chemical reactions. In most oxidative chemical reactions oxygen molecules participate and understanding of the activation mechanism of ...oxygen molecules is highly important. For this purpose, we applied surface‐enhanced Raman spectroscopy (SERS) to find out the mechanism of SPR‐assisted activation of oxygen, by using p‐aminothiophenol (PATP), which undergoes a SPR‐assisted selective oxidation, as a probe molecule. In this way, SPR has the dual function of activating the chemical reaction and enhancing the Raman signal of surface species. Both experiments and DFT calculations reveal that oxygen molecules were activated by accepting an electron from a metal nanoparticle under the excitation of SPR to form a strongly adsorbed oxygen molecule anion. The anion was then transformed to Au or Ag oxides or hydroxides on the surface to oxidize the surface species, which was also supported by the heating effect of the SPR. This work points to a promising new era of SPR‐assisted catalytic reactions.
Plasmon‐assisted reactions: Surface plasmon resonances (SPRs) support the activation of oxygen to yield metallic oxides and hydroxides on surfaces of Au and Ag nanoparticles, which selectively oxidize molecular species on the surface by laser light illumination. The electron donation to oxygen as well as a local heating effect in the presence of SPRs account for the activation of oxygen.
Conspectus Surface plasmons (SPs) originating from the collective oscillation of conduction electrons in nanostructured metals (Au, Ag, Cu, etc.) can redistribute not only the electromagnetic fields ...but also the excited carriers (electrons and holes) and heat energy in time and space. Therefore, SPs can engage in a variety of processes, such as molecular spectroscopy and chemical reaction. Recently, plenty of demonstrations have made plasmon-mediated chemical reactions (PMCRs) a very active research field and make it as a promising approach to facilitate light-driven chemical reactions under mild conditions. Concurrently, making use of the same SPs, surface-enhanced Raman spectroscopy (SERS) with a high surface sensitivity and energy resolution becomes a powerful and commonly used technique for the in situ study of PMCRs. Typically, various effects induced by SPs, including the enhanced electromagnetic field, local heating, excited electrons, and excited holes, can mediate chemical reactions. Herein, we use the para-aminothiophenol (PATP) transformation as an example to elaborate how SERS can be used to study the mechanism of PMCR system combined with theoretical calculations. First, we distinguish the chemical transformation of PATP to 4,4′-dimercaptoazobenzene (DMAB) from the chemical enhancement mechanism of SERS through a series of theoretical and in situ SERS studies. Then, we focus on disentangling the photothermal, hot electrons, and “hot holes” effects in the SPs-induced PATP-to-DMAB conversion. Through varying the key reaction parameters, such as the wavelength and intensity of the incident light, using various core–shell plasmonic nanostructures with different charge transfer properties, we extract the key factors that influence the efficiency and mechanism of this reaction. We confidently prove that the transformation of PATP can occur on account of the oxygen activation induced by the hot electrons or because of the action of hot holes in the absence of oxygen and confirm the critical effect of the interface between the plasmonic nanostructure and reactants. The products of these two process are different. Furthermore, we compare the correlation between PMCRs and SERS, discuss different scenario of PMCRs in situ studied by SERS, and provide some suggestions for the SERS investigation on the PMCRs. Finally, we comment on the mechanism studies on how to distinguish the multieffects of SPs and their influence on the PMCRs, as well as on how to power the chemical reaction and regulate the product selectivity in higher efficiencies.
Replacing inorganic anodes with organic electrode materials is an attractive direction for future green Li‐ion batteries (LIBs). Carbonyl compounds are being explored as leading anode candidates for ...organic LIBs. In particular, cyclohexanehexanone (C6O6), as a perfect structure composed entirely of six CO groups, can theoretically contribute to the most reactive sites and the highest specific capacity, but has not been used as an anode material so far owing to its high solubility in carbonate‐based electrolytes and extremely low electronic conductivity. Herein, C6O6 is first revealed as an ultra‐high capacity and high‐rate anode material through a total eight‐electron redox electrochemical process by effectively constructing an insoluble and highly conductive C6O6‐polymeric binder‐carbon network architecture. Experimental characterizations combined with first‐principles calculations elucidate that CO bonds in C6O6 can be lithiated to Li+ enolate (Li6C6O6) through a reversible six‐Li‐ion electrochemical process and further converted to Li8C6O6 dimers via a reversible two‐electron pseudocapacitive Li+ intercalation reaction. As such, the C6O6 anode shows an ultrahigh capacity of up to 1404 mAh g−1 at 200 mA g−1 and an extraordinary high‐rate durability (814 mAh g−1 after 700 cycles at 5.0 A g−1). A 4.3 V high energy/power density Li‐ion hybrid electrochemical capacitor based on the C6O6 anode is thus derived.
Cyclohexanehexone (C6O6) composed entirely of CO groups is first revealed as an ultra‐high capacity and high‐rate anode material for lithium‐ion batteries. Experimental characterizations combined with first‐principles calculations elucidate that CO bonds in C6O6 can be lithiated to Li+ enolate (Li6C6O6) through a reversible six‐Li‐ion electrochemical process and further converted to Li8C6O6 dimers via a reversible two‐electron pseudocapacitive Li+ intercalation reaction.
Electrocatalytic reduction of CO
to fuels and chemicals is one of the most attractive routes for CO
utilization. Current catalysts suffer from low faradaic efficiency of a CO
-reduction product at ...high current density (or reaction rate). Here, we report that a sulfur-doped indium catalyst exhibits high faradaic efficiency of formate (>85%) in a broad range of current density (25-100 mA cm
) for electrocatalytic CO
reduction in aqueous media. The formation rate of formate reaches 1449 μmol h
cm
with 93% faradaic efficiency, the highest value reported to date. Our studies suggest that sulfur accelerates CO
reduction by a unique mechanism. Sulfur enhances the activation of water, forming hydrogen species that can readily react with CO
to produce formate. The promoting effect of chalcogen modifiers can be extended to other metal catalysts. This work offers a simple and useful strategy for designing both active and selective electrocatalysts for CO
reduction.
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