查看更多>>摘要：Rational control of the compositions, morphologies and sizes of electrocatalyst are the key factors for achieving high performance of electrocatalytic reactions. Herein, a newly ultrathin PtRuRhCoNi high-entropy alloy nanowires (HEA-NWs) (~1.6 nm) catalyst is designed. The PtRuRhCoNi NWs/C achieved high mass activity of 7.68 A mg(PtRuRh)(-1), ultrahigh C1 selectivity of 78% for ethanol oxidation reaction. For hydrogen evolution reaction, the PtRuRhCoNi NWs/C also reached high mass activity, turnover frequency (11.99 A mg(PtRuRh)(-1), 31.9 s(-1), 0.5 M H2SO4 and 8.07 A mg(PtRuRh)(-1), 26.7 s(-1), 1 M KOH at -0.05 V vs. RHE) and stability. Theoretical calculations demonstrated that the excellent electroactivity of HEA is benefited by the self-complementary effect through strong orbital coupling, which maximized the electroactivity towards both oxidation and reduction and preferred binding of key intermediate. The design of pH-universal multifunctional catalyst by rational control of the compositions, morphologies and sizes strategy can facilitate the research of advanced catalysts.
查看更多>>摘要：The design of cathodic catalysts layer (CCL) consisted of Platinum Group Metal-free (PGM-free) electrocatalysts was done by catalyst coated membrane approach. Three different Fe-Mn-N-C compounds were synthesized with Fe:Mn ratio of 1:1, 2:1 and 2:1 with modified heat treatment profile. The catalysts were characterized by X-ray photoelectron spectroscopy, X-ray powder diffraction, pore and particle size distribution, zeta potential and transmission electron microscopy. Electrocatalysts were integrated into membrane electrode assembly and evaluated by electrochemical methods. Electrochemical impedance spectroscopy in combination with modeling were used for estimation of proton conductivity of CCL and its oxygen diffusivity. It was found that all CCLs possess extremely high proton conductivity, which was demonstrated for the first time for these types of PGMfree catalysts. The observed ORR mechanism was predominantly 4e- due to peroxide/radicals scavenging effect of Mn.
查看更多>>摘要：Oxygen evolution reaction (OER) in pH-neutral electrolyte is considered more difficult for the additional adsorption and the dissociation process of H2O. Herein, by in-suit construction of the heterostructure between MgO and NiCo2S4 on carbon cloth (CC), a novel MgO/NiCo2S4 heterostructure on CC (MgO/NCS-CC) is successfully fabricated. Benefitting from the optimized electronic structure attributed to the construction of heterointerface, and the intense adsorption of H2O on the surface of catalysts owing to the introduction of hydration-effect-promoting (HEP) element Mg, the MgO/NCS-CC exhibits outstanding OER activity with overpotential of 145 mV at the current density of 10 mA.cm(-2) in pH-neutral electrolyte and can maintain stability over 40 h. Density-functional theory (DFT) also demonstrates that the MgO/NiCo2S4 heterostructure can effectively adjust the electronic structure and enhance the adsorption of reactant, thus further optimizing Gibbs free energies and improving the activity for OER in pH-neutral electrolyte.
查看更多>>摘要：Lead-free double perovskites with superior stability have been considered as promising non-toxic substitutes to their lead-contained counterparts in photocatalysis. However, the severe charge recombination greatly restricts their potential as high-performance photocatalysts. Herein, for the first time, we present a self-assembled het-erostructure of lead-free double perovskite Cs2AgBiBr6 nanocrystals (NCs) on the surface of MXene nanosheets via mutual electrostatic attraction. The presence of MXene nanosheets effectively promotes the formation of free charge carriers inCs(2)AgBiBr(6 ) NCs via reducing the exciton binding energy. Additionally, the ultrafast photo-generated electron transfer from Cs(2)AgBiBr(6 )to MXene with a timescale of 1.1 ps largely prolongs the charge carrier lifetime by two times. As a result of the efficient charge separation and electron extraction, the Cs2Ag-BiBr6/MXene heterostructures achieve a high photoelectron consumption yield of 50.6 mu mol g(-1 )h(-1) for pho-tocatalytic CO2 reduction, which surpasses most previously reported lead-free perovskite-based catalysts.
查看更多>>摘要：NOx and VOCs are primary air pollutants and their photochemical reactions would generate secondary pollutants like O-3 with NO2 intermediate as the direct precursor. Here we apply a highly efficient In(OH)(3) photocatalyst to degrade mixed NO and C7H8 for inhibition of photochemical O-3 generation. The dual pollutants show synergistic interaction from the adsorption process to photocatalytic reaction. C7H8 and NO exhibit non-competitive adsorption and coupling reaction effects on In(OH)(3) surface. The coupling intermediate C7H7NOH would be oxidized to nitrotoluene and further decomposed into CO2 and nitrates. Meanwhile, the protons and electrons released during the oxidation of C7H8 can reduce NO to NH4+. Gibbs free energy calculation reveals that the coupling and reduction reactions are more favorable than the oxidation of NO to NO2. The new conversion path of NO on In(OH)(3) when C7H8 coexists could enable an increase of NO conversion efficiency to 100.0% and a decrease of NO2 selectivity to only 3.7%, thus highly inhibiting the formation of O-3.
Yu, Jimmy C.Wu, ChunxiaoZhu, RuixueTeoh, Wey Yang...
9页
查看更多>>摘要：We demonstrate a carefully tailored elemental red phosphorus (red P) for a record-high photocatalytic hydrogen evolution rate of 1280 mu mol g(-1 )h(-1). This performance has even surpassed some of the established compound photocatalysts. Systematic studies reveal that the bismuth-catalyzed selective growth of the preferential crystal phases of red P leads to the formation of fibrous and Hittorf's phases at distinctive sites within the same pho-tocatalyst particle of dendritic morphology: nanobranches of fibrous phase and main stems of Hittorf's phase. As each crystal phase possesses unique band energy potential, the intimate heterojunction between the two phases affords an effective built-in driving force for the efficient transportation of photoexcited charge carriers with suppressed charge trapping and recombination. The strategy in crystal phase engineering of red P as well as the understanding of its charge transportation properties in this work provides new insights into developing favorable elemental P-based materials for various photocatalytic applications.
查看更多>>摘要：Exploring excellent catalysts for oxygen reduction reaction (ORR) with a facile and cost-effective method is desirable but remains challenging. Herein, ultra-small PtCu3 nanoparticles (ca. 2.7 nm), immobilized on reduced graphene oxide (rGO), were synthesized via a novel and general strategy. Traceless protectant, NH4OH, was used to resist the aggregation of graphene oxide (GO), and the spray-freeze-drying method ensures excellent dispersion of the Pt and Cu precursors, which could not be achieved by other reported drying methods. After annealing, the nanoparticles with the highest mass loading, 52%, among reported ordered Pt-based catalysts were obtained. The PtCu3/rGO shows a remarkable electrocatalytic performance. Density functional theory calculations elucidate that PtCu3 possess a lowered energy barrier of the rate-determining step, contributing to significantly improved ORR kinetics. This strategy was extended to the synthesis of other binary- and quaternarymetallic Pt-based nanoparticles, which proved its generality and applicability towards the potential commercialization of fuel cell technologies.
查看更多>>摘要：The infeasible cost of PEMFCs can be effectively lowered by replacing Pt-based catalysts with PGM-free catalysts. Although promising advancements have been achieved recently, the practical availability of PGM-free catalysts in PEMFCs remains apprehensive, typically, owing to their low output power density. Herein, a huge breakthrough has been made for high power density PGM-free PEMFCs with a peak power density of 1.36 W cm-2 in H-2-O-2 and 0.65 W cm-2 in H2-air PEMFCs. Moreover, after iR-corrected, it delivers an affirmative current density of 62 mA cm-2 at 0.9 V in H-2-O-2 fuel cells, a breakthrough on the US Department of Energy 2025 target for PGM-free catalysts. The tremendous progress can be attributed to the rearrangement of active sites by recrystallization which significantly increases the active site density and mesoporosity of the Fe/N/C catalyst. Consequently, it cost-effectively enhances the catalytic activity and boosts its power density output.
查看更多>>摘要：The sluggish oxygen evolution reaction (OER) limits the efficiency of overall water splitting, which thereby hinders hydrogen evolution reaction (HER). Here, we demonstrate a bifunctional CoNiP nanosheet integrated electrode (CoNiP-NIE) to boost HER and replace OER by 5-hydroxymethylfurfural oxidation reaction (HMFOR) to obtain high-valued 2,5-furandicarboxylic acid (FDCA). The as-developed CoNiP-NIE exhibits a constant high Faradaic efficiency more than 82% for HMFOR in a wide potential from 1.40 V to 1.70 V vs. RHE, which stand at the top level among the reported electrocatalysts. Moreover, the low overpotential for HER further indicates its high efficiency in the H2 generation. Based on the bifunctional activity of CoNiP, an electrochemical hydrogen evolution coupled with biomass oxidation device is constructed, which delivers lower voltage (1.46 V) for anode oxidation and higher evolution rate of H-2 (41.2 L h(-1) m(-2)) than water splitting (1.76 V, 16.1 L h(-1) m(-2)).
查看更多>>摘要：This work reports a strategy to promote the low-temperature CO2 methanation on the Ni-based catalyst by tuning the surface oxygen vacancy and medium-strength basic sites of the CeO2 support and thus changing the reaction pathway. La species was introduced into CeO2 support and calcined at 600 degrees C (CeO2-La-600) to form a La-Ce-O solid solution with a thin La2O2CO3 layer on the surface, generating more basic sites and oxygen vacancies. This unique structure facilitated the adsorption and direct dissociation of CO2. Over Ni/CeO2-La-600, the reaction follows the HCOO* and *CO pathways, while over Ni/CeO2-600, the reaction occurs via the HCOO* pathway only. The decomposition of CO2 * to *CO is energetically more favorable than hydrogenation to HCOO* on Ni/CeO2-La-600, resulting in its higher catalytic performance at low temperatures. This work unravels the complex interplay among oxygen vacancy, basic site, and reaction pathway in CO2 methanation over the Ni-based catalysts.
NSTL
Elsevier