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We prepared a highly active and stable cathode catalyst for a solid oxide electrolysis cell (SOEC), decorated with in situ exsolved Fe nanoparticles (NPs) socketed on La1.2Sr0.8Mn0.4Fe0.6O4−α (R.P.LSMF), toward the CO2 electrolysis reaction to produce CO selectively. This catalyst was derived from the perovskite structure of La0.6Sr0.4Mn0.2Fe0.8O3−δ (LSMF) by simple annealing in a H2 atmosphere and showed high current densities of 2.04, 1.43, and 0.884 A cm−2 at 850, 800, and 750 °C, respectively, at a voltage of 1.5 V with corresponding total polarization resistance values of 0.205, 0.326, and 0.587 Ω cm2, respectively, at an open circuit voltage. The highly improved performance should be ascribed to the in situ exsolved Fe NPs anchored on Ruddlesden–Popper oxide and to the increased contents of oxygen vacancies in R.P.LSMF. More importantly, this active catalyst also exhibited a stable voltage profile for 100 h operation at an constant current density of 1.8 A cm−2, suggesting that the catalyst Fe–R.P.LSMF proposed in this study is a highly promising candidate for use in an efficient SOEC cathode for CO2 electrolysis processes. more...

The lithium-ion batteries are recognized as the most promising energy storage system, but it still does not meet the power requirements of electric vehicle batteries owing to low volumetric energy density with the traditional graphite electrode system. In this study, we report the development of a novel electrode system fabricated by implantation of a solid electrolyte interphase (SEI) layer on the graphite surface. The SEI-implanted graphite electrode is made using a lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)-based electrolyte and cycled with a lithium tetrafluoroborate LiBF4-based electrolyte. This new electrode system shows significantly enhanced electrochemical properties owing to the rapid and efficient diffusion of Li ions through the SEI layer between the electrolyte and electrode. This graphite electrode with its pre-formed SEI layer achieves a reversible capacity of 357 mAh g−1 at 0.5 C after 50 cycles, which is significantly higher than that of commercial lithium-ion battery systems constructed with LiPF6 (312 mAh g−1). The resulting unique electrode system could present a new avenue in SEI research for high-performance lithium-ion batteries. more...

We report a highly improved cathode catalyst by doping fluorine anions in oxygen sites of Ruddlesden-Popper material for CO2 electrolysis to produce CO in solid oxide electrolysis cells (SOECs). Th... more...

Atomic layer deposition (ALD) is an efficient technique that allows atomic-level surface control of metal catalysts for the design and development of electrocatalytic materials. Herein, we report a strategy for efficient catalyst design using a particle ALD method to enhance the electrocatalytic glycerol-oxidation-reaction (GOR) performance. Atomically controlled thin SnO2 layers were deposited on a carbon-supported Pt nanoparticle (Pt/C) surface using the ALD technique. The resulting SnO2 overcoated Pt/C (ALD(SnO2)–Pt/C) was then heat-treated at 400 °C under a N2 atmosphere. The onset potential as a kinetic parameter decreased with ALD (SnO2) coatings. The turnover frequency (TOF) for the GOR showed similar values for the tested samples (TOF of Pt/C: 74.86 h−1 and TOF of ALD(SnO2)–Pt/C: 91.29 h−1). Interestingly, interactions between the ALD SnO2 overcoating and Pt nanoparticles improved the catalytic stability for the GOR, preventing sintering of Pt nanoparticle catalysts. This demonstrates that an ALD SnO2 coating on defect sites of Pt can diminish Pt sintering for the GOR. From the GOR in an electrochemical batch reactor, the ALD(SnO2)–Pt/C catalyst also generated more glyceraldehyde (GAD) product than uncoated Pt/C at a similar glycerol conversion level. The density functional theory (DFT) calculations suggest that the binding energies of glycerol and reaction intermediates change at the interface of the SnO2-coated Pt surface compared to those at the Pt surface only, thus affecting the reaction chemistry for the electrocatalytic GOR. This work highlights how we can control reaction performance measures such as catalytic stability and product selectivity by using the particle ALD technique for electrocatalytic reactions such as glycerol oxidation. more...

The selective and efficient electrocatalytic transformation of carbon dioxide (CO2) to multicarbon alcohols (e.g., C2H5OH and C3H7OH) is a challenge in renewable and sustainable energy research. Herein, a series of hybrid catalysts consisting of Cu nanoparticles supported on N-doped porous carbon (Cu/NPC) were prepared. It was demonstrated that the selectivity for C2H5OH or C3H7OH could be tuned by introducing N-doped porous carbon materials as cocatalysts with different pyridinic N contents, which could in situ produce a reactive CO intermediate from CO2. By varying the pyridinic N content, highly selective production of multicarbon alcohols was achieved using the Cu/NPC hybrid catalysts with a high faradaic efficiency for one pot production of multicarbon alcohols up to 73.3% at −1.05 V (vs. RHE). The faradaic efficiency for C2H5OH and C3H7OH was 64.6% and 8.7%, respectively. The pyridinic N species were likely the CO-producing sites and together with Cu catalytic sites acted cooperatively to produce C2H5OH and C3H7OH via a two-site mechanism for efficient CO2 reduction to multicarbon alcohols. These findings provide novel guidance for the rational design of electrocatalysts and for tuning the catalytic activity and selectivity for multicarbon alcohol production from CO2. more...

We developed a new and efficient sulfur-tolerant catalyst for application as a solid oxide electrolysis cell (SOEC) cathode designed with in situ exsolved CoNi alloy nanoparticles anchored on a Ruddlesden–Popper (R.P.) support of La1.2Sr0.8Co0.4Mn0.6O4 and evaluated its catalytic activity for CO2 electrolysis to CO under a CO2 gas stream containing H2S species. This catalyst was prepared by in situ annealing of a perovskite derivative (La0.6Sr0.4Co0.5Ni0.2Mn0.3O3) in a 20% H2/N2 gas at 800 °C. The catalyst exhibited good reversibility of structural transitions during reduction and re-oxidation processes. A high current density of 703 mA cm−2 was achieved at 1.3 V and 850 °C with a maximum faradaic efficiency of 97.8%. In situ grown CoNi alloy nanoparticles and the high oxygen vacancy content in the R.P. support were responsible for its high catalytic activity and efficiency. Importantly, no sign of performance degradation was observed in galvanostatic tests over a period of 90 h operation under H2S-containing CO2 gas conditions. Moreover, the catalyst showed no noticeable structural changes even after exposure to 100 ppm H2S/N2, indicating that the catalyst developed in this study is highly active for CO2 electrolysis with a high tolerance against sulfur-poisoning species. Therefore, this Ruddlesden–Popper material with in situ exsolved CoNi alloy nanoparticles should be a promising cathode catalyst for practical application to H2S-containing CO2 gas streams that are effluents of power stations or steel making plants. more...

Converting CO2 into useful chemicals through an electrocatalytic process is an attractive solution to reduce CO2 in the atmosphere. However, the process suffers from high overpotential, low activity, or poor product selectivity. In this study, N,S dual-doped carbon nanoweb (NSCNW) materials were proposed as an efficient nonmetallic electrocatalyst for CO2 reduction. The NSCNW catalysts preferentially and rapidly converted CO2 into CO with a high Faradaic efficiency of 93.4 % and a partial current density of -5.93 mA cm-2 at a low overpotential of 490 mV. A small Tafel slope value (93 mV dec-1 ) was obtained, demonstrating a high rate for CO2 reduction. Moreover, the catalysts also exhibited a quite stable current-density profile during 20 h with a high CO Faradaic efficiency above 90 % throughout the electrolysis reaction. The high catalytic performance of the catalysts for CO2 reduction could be attributed to synergistic effects associated with the structural advantages of 3 D carbon nanoweb structures and effective S doping of the carbon materials with the highest ratio of thiophene-like S to oxidized S species. more...

We report a highly active Ruddlesden-Popper material with a mechanism of in situ exsolution of Co nanoparticles and its use as an effective catalyst for CO2 reduction to produce CO in a solid oxide electrolysis cell. This catalyst is simply prepared by transforming a perovskite of La0.6Sr0.4Co0.7Mn0.3O3 and revealed a good reversibility of structural transition between the Ruddlesden-Popper and the perovskite structure during reaction cycles. A very high current density of 630 mA/cm2 can be accomplished at a voltage of 1.3 V and temperature of 850 °C with a very high Faraday efficiency of 95% or larger. More importantly, no sign of degradation is indicated as observed by galvanostatic stability test, implying that this Ruddlesden-Popper structure is highly robust as the cathode catalyst for the CO2 electrolysis. In situ exsolved Co nanoparticles and high concentration of oxygen vacancies caused by the structural transition are responsible for its high stability and catalytic activity, as characterized by several physicochemical analyses. more...

Current lithium-ion batteries have a low theoretical capacity that is insufficient for use in emerging electric vehicles and energy-storage systems. The development of lithium-sulfur batteries utilizing Li2 S cathodes would be a promising option to overcome the capacity limitation. In this work, new three-dimensional (3D) honeycomb-like N-doped carbon nanowebs (HCNs) have been synthesized through a facile aqueous solution route for use as a cathode material in lithium-sulfur batteries. The Li2 S@HCNs cathode delivers a high discharge capacity of approximately 815 mAh g-1 after 65 cycles at 0.1 C, along with a superior rate capacity of approximately 568 mAh g-1 even at 2 C. The outstanding electrochemical rate performance is ascribed to their unique 3D honeycomb-like nanoweb structure, consisting of nanowires derived from polypyrrole. These properties greatly enhance the electrochemical reaction kinetics by providing efficient electron pathways and hollow channels for electrolyte transport. Nitrogen doping in the carbon nanowebs also considerably improves the chemisorption properties by tuning affinity between sulfur and oxygen functional groups on the carbon framework. The simple synthesis strategy and the resulting unique electrode structure could present a new avenue in nanostructure research for high-performance lithium-sulfur batteries. more...

In this paper, an anode material system of Co3O4 nanowires composited with reduced graphene oxide (Co3O4 NWs/rGO) and protected by N-doped carbon layer (Co3O4 NWs/rGO@NC) was prepared for lithium ion batteries. The N-doped carbon layer could serve as stress relief matter to reduce volume changes of the Co3O4 NWs/rGO during repeated charge/discharge cycles, and also enhance the reaction kinetics as a highly conductive layer between the Co3O4 NWs and electrolyte. The Co3O4 NWs/rGO@NC electrode delivered a high discharge capacity of ca. 995 mAh g−1 at 0.1 C after 65 cycles, and showed a much better rate performance of 428 mAh g−1 even at a high current rate of 5 C as compared to those of Co3O4 NWs/rGO electrode (203 mAh g−1). The demonstrated electrochemical properties suggested that the N-doped carbon coating on the composite of Co3O4 NWs and rGO could significantly enhance the durability and rate capability of the anode material for high performance lithium ion batteries. more...

The kinetic influences of transition metals (TMs) in non-platinum group metal (non-PGM) catalysts using ethylenediamine-TM (en-TM) complex are studied for the electro-reduction of oxygen. We exhibit that Ni atoms are inefficiently dispersed, which may influence the N doping as evidenced by XPS and elemental maps. High concentrations of N are attributed to the well-dispersed Co and Fe over the carbon. Electrochemical measurements demonstrate that the ORR on Co@NC and Fe@NC catalysts takes place faster than that on NC and Ni@NC catalysts. The correlation between the quaternary-N concentration of species and the onset potential with respect to TMs is investigated. more...

The electrochemical conversions of CO2 to valuable products have gained much interest to mitigate the increasing CO2 concentration in the atmosphere. Selective syntheses of differently shaped tin (Sn) catalysts of rod, rectangular sheet, and dendrite structures were reported here using a new solar electro-deposition method, and their catalytic performance was investigated for the electrochemical reduction of CO2 to liquid fuel in an electrolyte solution of CO2 dissolved pure water. The crystal orientation and structural properties of the prepared Sn catalysts were investigated by XRD and SEM analyses. The selective formation of HCOOH on the prepared Sn electrocatalyst was observed with high faradaic efficiency and HCOOH formation rate over the rod shaped Sn catalysts, resulted in a maximum faradaic efficiency of 94.5% at 1.6 V vs Ag/AgCl and a maximum formation rate of about 0.5 mol/gcat h at 2 V vs Ag/AgCl. The present work may open up a new approach for a selective catalyst synthesis of known structural properties for effective CO2 reduction reaction. more...

Ruthenium oxide/cobalt oxide composite nanowires (RuO2/Co3O4 NWs) have been synthesized via a simple and efficient electrospinning method for use as bifunctional electrocatalysts in rechargeable lithium-oxygen (Li-O2) battery cathodes. The as-prepared NWs have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and X-ray absorption near-edge structure (XANES) spectroscopy. The intrinsic activities of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) over the obtained composite NWs are studied using a rotating disk electrode (RDE) technique. The RuO2/Co3O4 NWs exhibit superior bifunctional electrocatalytic activities for both the ORR and the OER when compared to the activities of the Co3O4 NWs and only Ketjenblack (KB). When the RuO2/Co3O4¬ NWs are employed as cathode catalysts in Li-O2 cells, great improvements in terms of the discharge capacity, coulombic efficiency, and cycle stability with low discharge-charge overpotentials are achieved. These can be attributed to the high bifunctional catalytic activities of the RuO2/Co3O4 composite NWs. more...

In this study, a highly efficient Pd catalyst supported on a conducting polymer-carbon composite was prepared for electro-oxidations of ethanol and formic acid. A polypyrrole-carbon composite was synthesized and modified by doping camphor sulfonic acid (CSA) during the polymerization step of pyrrole at room temperature. The resulting CSA-doped polypyrrole-carbon composite (PPyCC) showed significantly increased specific surface area and enhanced electrical conductivity compared with a polypyrrole-carbon composite without doping (PPyC). From the electrochemical tests, it was observed that the Pd-supported on CSA-doped polypyrrole-carbon composite (Pd/PPyCC) exhibited much larger electrochemical surface area (ECSA), enhanced catalytic activity and high durability towards the oxidations of ethanol and formic acid. The results indicate that the camphor sulfonic acid serving as both dopant and surfactant could improve the electrical conductivity and morphology of support material with enhanced interaction between Pd nanoparticles and support material. more...

Converting CO2 into valuable chemicals using electrocatalysis is an attractive approach for sustainable energy storage and artificial carbon cycle. In this study, atomically dispersed Ir species (Ad-Ir) that are supported on three-dimensional (3D) porous carbon networks are proposed as electrocatalysts for highly efficient CO2 conversion. The resulting catalysts can preferentially and rapidly produce CO with a high Faradaic efficiency of 95.6 % and a very high turnover frequency (TOF) value of 33,365 h−1. Furthermore, it shows no obvious decay in both FE for CO and current density over 20 h of continuous operation. Based on detailed experimental studies and density functional theory (DFT) calculations, such outstanding catalytic performance for CO2 conversion to CO production can be attributed to the structural advantages of 3D network of porous carbon and atomically dispersed Ir species on the 3D carbon support. more...

Recently, lithium‐ion batteries have reached the limit of low reversible capacity that is deficient for uses in emerging electric devices for mobiles and electric vehicles (EVs). In this work, we have prepared polygonal-stacked Cu2O (PCO) through modified Benedict's reaction by simply controlling concentrations of cetyltrimethylammonium bromide (CTAB). The synthesized PCO materials featuring sharp tip structure showed enhanced capacity than round edge structured PCO. Surface area and structural difference could play critical roles in the electrochemical performances of the PCO materials. Among three different structured Cu2O materials, sharp tip shaped PCO electrode exhibited a high discharge capacity of ca. 402 mAh/g at the 2nd cycle and its discharge capacity appeared to gradually increase to ca. 506 mAh/g up to the 100th cycle. The diffusion coefficient of sharp tip shaped PCO was also larger than PCO with round-structured morphology. The simple synthesis strategy for the resulting unique electrode morphology can allow to understand morphology effects on anode materials for lithium-ion batteries. more...

The design of the cost-effective, efficient, and durable electrocatalysts for hydrogen evolution reaction (HER) is of great importance in the field of clean and renewable energies. In this study, Ni/NiO nanocomposite supported on N-doped carbon nanoweb (Ni/NiO/NCW) hybrid materials are proposed as an efficient electrocatalyst for HER in alkaline media. A series of Ni/NiO/NCW hybrid catalysts were prepared via polymerization of polypyrrole (PPy) in the presence of a surfactant, followed by incipient wetness impregnation and heat treatment techniques. The resulting Ni/NiO/NCW hybrid catalysts exhibit an excellent electrocatalytic properties with a lower overpotential of 105.3 mV (vs RHE) at 10 mA cm−2, a smaller value of Tafel slope (55.2 mV dec−1) and almost 100% Faradaic efficiency. It also shows good stability in performance attenuation during continuous cyclic voltammetry sweeps for 1000 cycles. Its excellent electrocatalytic performance for alkaline hydrogen evolution reaction can be attributed to the synergistic effect associated with the morphological benefit of 3D N-doped carbon nanoweb and Ni/NiO heterostructure with the optimal ratio of Ni to NiO. more...

Recently, oxygen vacancy engineering represents a new direction for rational design of high-performance catalysts for electrochemical CO2 reduction (CO2RR). In this work, a series of amorphous MnOx catalysts with different concentrations of oxygen vacancies, namely, low (a-MnOx-L), pristine (a-MnOx-P), and high oxygen vacancy (a-MnOx-H), have been prepared by simple plasma treatments. The resultant a-MnOx-H catalyst with a larger amount of oxygen vacancy on the catalyst surface is able to preferentially convert CO2 to CO with a high Faradaic efficiency of 94.8% and a partial current density of 10.4 mA cm−2 even at a relatively lower overpotential of 510 mV. On the basis of detailed experimental results and theoretical density functional theory (DFT) calculations, the enhancement of CO production is attributable to the abundant oxygen vacancies formed in the amorphous MnOx which should favor CO2 adsorption/activation and promote charge transfer with the catalyst for efficient CO2 reduction. more...

Metal-free catalysts have gained substantial attention as a promising candidate to replace the expensive platinum (Pt) catalysts for the oxygen reduction reaction (ORR) which is a key process in low temperature fuel cells. Development of highly efficient and mass-producible N-doped carbon catalysts, however, remains to be a great challenge. In this study, N-doped porous carbon (NPC) materials were synthesized via a simple, cost-effective and scalable method for mass production by using the D-gluconic acid sodium salt, pyrrole, Triton X-100 and KOH. The resulting NPC possessed a multidirectional porous carbon network (SBET: 1026.6 m2 g−1, Vt: 1.046 cm3 g−1) with hierarchical porosity and plenty of graphitic N species (49.1%). Electrochemical tests showed that the NPC itself was highly active for the ORR under alkaline and acidic conditions via a four electron pathway for the complete reduction of O2 in water. More importantly, this NPC catalyst demonstrated better performance than commercial Pt/C catalysts in terms of long-term durability and methanol tolerance under both conditions. more...