查看更多>>摘要：S-scheme heterojunction has attracted much attention due to its unique structure and interface interaction. Herein, AgBr/BiOBr heterojunction with surface oxygen vacancies (OVs) was in situ synthesized by a facile chemical method. It was found that the evolution rates of photoreduction of CO2 to CO and CH4 with 0.33AB are 212.6 and 5.7 mu mol g(-1) h(-1) respectively, which are 9.2 and 5.2 times higher than those of pure BiOBr. It was demonstrated that the S-scheme band structure could improve the utilization of sunlight, increase the reduction power of photogenerated electrons, and enhance the separation and transfer of photogenerated charge carriers. Furthermore, the OVs on the surface of BiOBr for AgBr/BiOBr heterojunction are conductive to the adsorption and activation of CO2 molecules. The synergetic effect of S-scheme band structure and OVs on photocatalytic reduction of CO2 was discussed. The work provides a facile method for in situ construction of S-scheme heterojunction with defect for CO2 photoreduction.
查看更多>>摘要：Cu2O clusters/TiO2 nanosheet (CNSX) as a photocatalyst is created to tailor the selectivity of CO2 photoreduc-tion. The catalysts show different selectivity of CO and CH4 with the increase of Cu2O mass. TiO2 nanosheet (NS) exhibits 100% selectivity of CH4 with a rate of 37.6 mu mol g(-1) h(-1). However, CO2 would be converted to CO with selectivity of 98% and yield of 162.6 mu mol g(-1) h(-1) on 5 wt% Cu2O/TiO2 nanosheet (CNS3). The Ti center dot center dot center dot CO2-center dot center dot center dot Ti coordination intermediate on Ti3+ sites is responsible for CH4 formation, whereas the Cu center dot center dot center dot CO2 center dot center dot center dot Ti specie on Cu1-delta and Ti4+delta sites determines CO production. The Cu+-Ti3+ interface interaction on CNSX surface can generate Cu1-delta and Ti4+delta sites and eliminate Ti3+ via the charge transfer from Ti3+ to Cu+. The selectivity is thus tailored effectively by Cu+-Ti3+ interface interaction mediated CO2 coordination model. This work would offer a new perspective for tailoring the selectivity of CO2 photoreduction.
查看更多>>摘要：Localized surface plasmon resonance (LSPR) can effectively improve the catalytic activity of electrocatalysts by using solar energy. However, the application of LSPR effect in the electrochemical nitrogen reduction reaction (ENRR) is still blank and the ability of LSPR to enhance the catalytic activity of ENRR is unclear. Herein, the effective enhancement for the NRR electrocatalytic activity of Au nanorods (NRs) under illumination conditions based on the LSPR effect was successfully achieved. Under the irradiation of 808 nm laser (80 mW cm-2), the rate of ammonia yield increased about 63.6% with comparison of that in dark. Meanwhile, combined with the results of the Finite difference time domain method (FDTD) simulation and photocurrent analysis, it is proved that the hot electrons excited by LSPR effect can effectively promote the ENRR catalytic activity of Au NRs. This study provides an important reference for the design of a novel LSPR-promoted electrocatalyst for NRR.
查看更多>>摘要：It is a challenging task to overcomes the bottleneck of N2 adsorption and activation in N2 reduction reaction (NRR). Regulating the catalyst surface electronic state is treated as a potential strategy to prevail over the barrier. Here, Incorporating Fe as a dopant in the TiO2 nanoparticles can generate oxygen vacancies and dopant energy levels, promoting the adsorption and activation of N2 molecules. F surface modification induces Fe (III) in the high spin state and upshifts the dopant energy level. That facilitates Fe 3d electrons backdonation to N 1ag* orbital promotes the activation of N2 molecule and reduces the limiting potential of NRR. Therefore, F-Fe: TiO2 electrocatalyst achieved the highest Faradaic efficiency and maximum NH3 production rate of 27.67% and 27.86 mu g h-1 mgcat. -1 at -0.5 V v.s. reversible hydrogen electrode. This work provides deep insights into the design surface electronic state of catalyst toward efficient N2 to NH3 conversion.
查看更多>>摘要：To elucidate the evolution of ionomer-Pt and ionomer-carbon interfaces during life cycle of polymer electrolyte fuel cells (PEFCs), electrodes with high surface area (HSA) and durable carbon supports underwent catalyst and carbon corrosion accelerated stress tests (ASTs) under stoichiometric and sub-stoichiometric gas flow conditions. Electrochemical characterizations, as well as X-ray photoelectron spectroscopy (XPS) were utilized to assess degree of components degradation. Catalyst AST results revealed that Pt nanoparticles dispersed within the micro- and meso-pores and not in contact with ionomer are the main contributor to the 50% electrochemical surface area (ECSA) loss observed after 30k cycles resulting in significant polarization loss, which is much more notable in the case of sub-stoichiometric operating condition. Support AST results for HSA carbon showed severe ionomer degradation and 55% ECSA loss within the first 100 cycles, while cell with durable support exhibited negligible polarization and ECSA decay during the first 2500 cycles attributed to higher ionomer coverage, preservation of proton pathways preventing Pt from detachment.
查看更多>>摘要：Alkaline fuel cells (AFCs) are relevant for niche applications, but still require enhanced performance and lifetime. Active and durable hydrogen oxidation reaction (HOR) catalysts must be developed: linking their electrochemical surface area (ECSA) loss to their HOR activity and understanding whether the ECSA loss of carbonsupported platinum group metal-based (PGM/C) HOR catalysts is irreversible (nanoparticles dissolution, detachment, Ostwald ripening) or reversible is pivotal. Using identical-location transmission electron micrographs (IL-TEM) and ECSA characterizations by "CO-like" stripping undertaken pre and post accelerated stress tests (AST), the different degradation mechanisms undergone by monometallic (Pt/C and Pd/C) and bimetallic catalysts (Pd-Pt/C and Pd-Ni/C) are unveiled. Monometallic PGM/C undergo extensive reversible poisoning and irreversible degradation upon operation at low potential, in contrast to bimetallic catalysts, which are less affected. Pd-Ni exhibits the smallest loss of ECSAPGM and HOR activity: it poorly catalyzes carbon corrosion and is hardly poisoned by "CO-like" species.
Sibi, Malayil GopalanKhan, Muhammad KashifVerma, DeepakYoon, Wonjoong...
15页
查看更多>>摘要：We present a tandem catalyst consisting of Na-promoted bifunctional FeAlOx (Na-FeAlOx) and Zn-doped HZSM-5, the outer surface of which was coated with a SiO2 layer (Zn-HZSM-5@SiO2). This tandem catalyst afforded a high BTEX space-time yield of 4.0 mmol g-1h-1 with a CO2 conversion of 45.2%. The selectivities toward BTEX were tuned by controlling the nature, density, and distribution of the Bronsted acid sites of the zeolites, in addition to adjusting the proximity between the Fe-based and zeolitic active sites. In situ operando experiments revealed the role of Zn-HZSM-5@SiO2 not only in dehydroaromatization, but also in CO2 adsorption, reverse water-gas shift reactions, and C-C coupling reactions. The findings of this study are promising for designing a tandem catalyst to directly convert CO2 to BTEX in high yields, and also provide novel insights into the reaction intermediates for this tandem catalyst.
查看更多>>摘要：In this work, a novel van der Waals (vdW) heterojunction composite combining g-C3N4 with nitrogen vacancies and Tp-Tta COF manifests effective interface contact area and excellent photocatalytic CO2 reduction performance. First-principles density functional theory calculation and experimental results suggest that the presence of nitrogen vacancies in g-C3N4 can widen the Fermi level gap between C3N4 (NH) and Tp-Tta COF, promoting the recombination of invalid photogenerated carriers through S-scheme pathway. Benefitted from the accelerated transfer of photogenerated charges at the vdW heterostructure interface, the deactivation of oxygen vacancies in C3N4 (NH)/COF is prevented and much higher photocatalytic activity and stability are obtained. The efficient electron transfer and the affinity of Tp-Tta for CO2 are beneficial to the enhanced CO selectivity. This work provides insights for the design of S-scheme heterojunction photocatalyst for CO2 reduction.
查看更多>>摘要：As a key factor for chemical looping steam methane reforming, the oxygen carrier with high quality is essential. In this work, both high reactivity and coking resistance of the La1-xSrxMn1-yCoyO3+delta oxygen carriers are achieved by double adjustment of Co and Sr. The redox tests and characterization results showed that the introduction of cobalt provided surface active sites to accelerate the activation of methane on the surface, and the Sr doping increased the oxygen vacancies which facilitated the migration of oxygen anion in the bulk of the oxygen carrier particles. The doping of Co and Sr can match the supply of oxygen from the bulk and the need of oxygen on the surface of the oxygen carrier particles. The best substitution proportion of Co and Sr could be set in range of 0.4-0.5 and 0.2-0.4, respectively. The La0.8Sr0.2Mn0.5Co0.5O3+delta exhibited satisfactory performance and good stability in the cyclic redox tests.
Fu, Hong ChuanWang, Xiao HuChen, Xiao HuiZhang, Qing...
8页
查看更多>>摘要：Promoting water dissociation kinetics and hydrogen desorption ability is the key challenge of tungsten carbides for boosting hydrogen evolution reaction (HER) in alkali environment. Here, we report that an interfacial engineered W2C-Ni(OH)(2) electrocatalyst consisting of Ni(OH)(2) layer-encapsulated W2C nanowire array can afford current densities of 10 and 100 mA cm(-2) with overpotentials of only 60 and 213 mV in 1.0 M KOH, respectively, which not only surpasses the most previously reported W2C-based examples, but even outperforms the commercial Pt/C catalyst at high current densities. The experimental results based on the classic bifunctional mechanism suggest that Ni(OH)(2) mainly acts as the scissors for the dissociation of water, and the W2C site serves as the location for the adsorption and desorption of hydrogen. Further density functional theory calculations reveal that the hybridization of W2C with Ni(OH)(2) can also alleviate the strong tungsten-hydrogen bond, further optimizing the hydrogen adsorption energy of the hybrid.
NSTL
Elsevier