Abstract Electrochemical nitrate reduction (NITRR) offers a promising alternative toward nitrogen recycling and ammonia production under ambient conditions, for which highly active and selective electrocatalyst is desired. In this study, metallic cobalt nanoarrays as facilely prepared from the electrochemical reduction of Co(OH) 2 nanoarrays (NAs) are demonstrated to exhibit unprecedented NH 3 producing capability from catalyzing NITRR. Benefitting from the high intrinsic activity of Co 0 , intimate contact between active species and conductive substrate and the nanostructure which exposes large number of active sites, the Co‐NAs electrode exhibits current density of −2.2 A cm −2 and NH 3 production rate of 10.4 mmol h −1 cm −2 at −0.24 V versus RHE under alkaline condition and significantly surpasses reported counterparts. Moreover, the close‐to‐unity (≥96%) Faradaic efficiency (FE) toward NH 3 is achieved over wide application range (potential, NO 3 − concentration and pH). Density function theory calculation reveals the optimized adsorption energy of NITRR intermediates on Co surface over Co(OH) 2 . Furthermore, it is proposed that despite the sluggish kinetics of Volmer step (H 2 O → *H + *OH) which provides protons in conventional hydrogenation mechanism, the proton‐supplying water dissociation process on Co surface is drastically facilitated following a concerted water dissociation–hydrogenation pathway.
Energy-saving electrolytic hydrogen production could be realized by replacing sluggish oxygen evolution reaction (OER) with ethanol oxidation reaction (EOR). In this study, a C@NiP-Pd bifunctional catalyst is fabricated towards EOR and hydrogen evolution with high activity (close to the theoretical potential), selectivity, and stability (anti-poisoning). The potential of EOR is reduced by 1.072 V relative to OER at 100 mA cm-2. In the water-ethanol co-electrolysis device, the onset potential is as low as 0.4 V, the power consumption of device is still lower than the water electrolysis theory at high current density. High-selective acetate could be co-produced with hydrogen while without CO2 emission. The high selectivity is derived from the abundant OH* on the surface of Ni, which promotes the conversion of *CH3CO adsorbed on Pd to *CH3COOH. This study provides a new straight to design high-performance electrocatalysts for energy-saving co-generation of hydrogen and value-added chemicals while without CO2 emissions.
Abstract The development of industry and agriculture has been accompanied by an artificially imbalanced nitrogen cycle, which threatens human health and ecological environments. Electrocatalytic systems have emerged as a sustainable way of converting nitrogen‐containing molecules into high value‐added chemicals. However, the construction of high‐performance electrocatalysts remains challenging. The development of oxygen vacancy engineering strategy has promoted more research efforts to explore the structure‐activity relationship between catalytic activity and oxygen vacancies. This review systematically summarizes the recent development of oxygen vacancies‐rich metal oxides for electro‐catalyzing nitrogen cycling systems, involving electrocatalytic nitrate reduction reaction, nitric oxide reduction reaction, nitrogen reduction reaction, C─N coupling, urea oxidation reaction, and nitrogen oxidation reaction. First, the construction methods and characterization methods of oxygen vacancies are summarized. Then, the effect of oxygen vacancy on electrocatalytic activity of metal oxides is discussed in terms of regulating the electronic structures of electrocatalysts, improving the electroconductivity of catalysts, lowing the energy barrier, and strengthening adsorption and activation of intermediate species. Finally, future directions for oxygen vacancy engineering and electrocatalytic nitrogen cycle are anticipated.
Abstract Atomically dispersed sites anchored on small oxide clusters are attractive new catalytic materials. Herein, we demonstrate an electrical pulse approach to synthesize atomically dispersed Pt on various oxide clusters in one step with nitrogen‐doped carbon as the support (Pt 1 −MO x /CN). As a proof‐of‐concept application, Pt 1 −FeO x /CN is shown to exhibit high activity for oxygen reduction reaction (ORR) with a half‐wave potential of 0.94 V vs RHE, in contrast to the poor catalytic performance of atomically dispersed Pt on large Fe 2 O 3 nanoparticles. Our work has revealed that, by tuning the size of the iron oxide down to the cluster regime, an optimal OH* adsorption strength for ORR is achieved on Pt 1 −FeO x /CN due to the regulation of Pt−O bonds. The unique structure and high catalytic performance of Pt 1 −FeO x /CN enable the Zinc‐Air batteries an excellent performance at ultralow temperature of −40 °C with a high peak power density of 45.1 mW cm −2 and remarkable cycling stability up to 120 h.
The construction of an interface has been demonstrated as one of the most insightful strategies for designing efficient catalysts toward electrochemical CO 2 reduction (CO 2 RR). However, the weak interfacial interaction and inherent instability inevitably hinder a further performance enhancement in CO 2 RR attributable to the interface effect. Herein, 2 nm Ag nanoclusters (Ag NCs) are embedded onto CeO 2 nanospheres (CeO 2 NSs) with highly interconnected porosity (Ag NCs@CeO 2 NSs) to exclusively study the pure interface effect toward CO 2 RR. The enhanced Ag–CeO 2 pure interface endows Ag NCs@CeO 2 NSs with a remarkably larger current density, significantly higher Faraday efficiency (FE), and energy efficiency as compared to Ag NCs, CeO 2 NSs, and the one with Ag NCs dispersed on CeO 2 nanoparticles. More importantly, an impressively high CO FE of over 70.0% is achieved at an ultralow overpotential ( η ) of 146 mV. The free energy and differential charge calculations, coupled with X‐ray photoelectron spectroscopy results jointly imply that the effective initiation of CO 2 RR to CO at a lower η over Ag NCs@CeO 2 NSs derives from the enhanced interface‐induced charge delocalization, which enhances the electron transfer ability toward *COOH intermediate, thus overcoming the energy barrier demanded for the rate‐determining step.
Cesium (Cs+) and strontium (Sr2+) ions are the main fission byproducts in the reprocessing of spent nuclear fuels for nuclear power plants. Their long half-live period (30.17 years for 137Cs and 28.80 years for 90Sr) makes them very dangerous radionuclides. Hence the solidification of Cs+ and Sr2+ is of paramount importance for preventing them from entering the human food chain through water. Despite tremendous efforts for solidification, the long-term stability remains a great challenge due to the experimental limitation and lack of good evaluation indicators for such long half-life radionuclides. Using density functional theory (DFT), we investigate the origin of long-term stability for the solidification of Cs+ and Sr2+ inside sodalite and establish that the exchange energy and the diffusion barrier play an important role in gaining the long-term stability both thermodynamically and kinetically. The acidity/basicity, solvation, temperature, and diffusion effect are comprehensively studied. It is found that solidification of Cs+ and Sr2+ is mainly attributed to the solvation effect, zeolitic adsorption ability, and diffusion barriers. The present study provides theoretical evidence to use geopolymers to adsorb Cs+ and Sr2+ and convert the adsorbed geopolymers to zeolites to achieve solidification of Cs+ and Sr2+ with long-term stability.
The Cover Feature shows the cogeneration of H2 and value-added formate from the electrolysis of methanol/water by a Ni–Co double hydroxide nanoneedle array bifunctional electrocatalyst obtained through a facile hydrothermal treatment. More information can be found in the Full Paper by M. Li et al. on page 914 in Issue 5, 2020 (DOI: 10.1002/cssc.201902921).
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