Pt nanodendrites with a PtIr alloy surface structure exhibit excellent stability toward acidic hydrogen evolution reaction

The development of effective and stable electrocatalysts for the hydrogen evolution reaction(HER)in acidic electrolytes is a significant challenge.In this work,homogeneous Pt nanodendrites(Pt NDs)with a PtIr shell were successfully synthesized by a two-step wet chemical method.This open three-dimensional(3D)dendritic structure exhibited exceptional electrocatalytic characteristics,exposing as many active sites as feasible.Furthermore,by alloying Ir with Pt on the surface,catalytic activity was greatly enhanced while ensuring extremely high stability.Iridium surface-enriched platinum nanodendritic catalysts(Pt@PtIr NDs)outperformed the control samples and the commercial catalysts.In acidic HER test,Pt@PtIr NDs had a lower overpotential(22 mV)than Pt NDs(26 mV)and commercial Pt/C(31 mV)at 10 mA/cm2,and the activity of Pt@PtIr NDs remained consistent even after undergoing a continuous durability test for at least 168 h,which was much superior to the performance of commercial Pt/C(10 h)under identical test conditions.This study revealed that the application of 3D Pt dendritic metal alloys may offer a chance for the development of enhanced electrocatalysts in acidic HER.

Synergetic effects of gold-doped copper nanowires with low Au content for enhanced electrocatalytic CO_(2)reduction to multicarbon products

As efficient catalysts of electrochemical CO_(2)reduction reaction(CO_(2)RR)towards multicarbon(C_(2+))products,Cu-based catalysts have faced the challenges of increasing the reactive activity and selectivity.Herein,we decorated the surface of Cu nanowires(Cu NWs)with a small amount of Au nanoparticles(Au NPs)by the homo-nucleation method.When the Au to Cu mass ratio is as little as 0.7 to 99.3,the gold-doped copper nanowires(Cu-Au NWs)could effectively improve the selectivity and activity of CO_(2)RR to C_(2+)resultants,with the Faradaic efficiency(FE)from 39.7%(Cu NWs)to 65.3%,the partial current density from 7.0(Cu NWs)to 12.1 mA/cm^(2) under−1.25 V vs.reversible hydrogen electrode(RHE).The enhanced electrocatalytic performance could be attributed to the following three synergetic factors.The addition of Au nanoparticles caused a rougher surface of the catalyst,which allowed for more active sites exposed.Besides,Au sites generated*CO intermediates spilling over into Cu sites with the calculated efficiency of 87.2%,which are necessary for multicarbon production.Meanwhile,the interphase electron transferred from Cu to Au induced the electron-deficient Cu,which favored the adsorption of*CO to further generate multicarbon productions.Our results uncovered the morphology,tandem,electronic effect between Cu NWs and Au NPs facilitated the activity and selectivity of CO_(2)RR to multicarbons.

Tunable CO_(2)enrichment on functionalized Au surface for enhanced CO_(2)electroreduction

Electrochemical conversion of carbon dioxide(CO_(2))to higher-value products provides a forward-looking way to solve the problems of environmental pollution and energy shortage.However,the low solubility of CO_(2)in aqueous electrolytes,sluggish kinetics,and low selectivity hamper the efficient conversion of CO_(2).Here,we report a Au-based hybrid nanomaterial by modifying Au nanoparticles(NPs)with the macrocyclic molecule cucurbit[6]uril(Au@CB[6]).Au@CB[6]displays the optimal selectivity of CO,with the highest CO Faraday efficiency(FECO)reaching 99.50%at−0.6 V vs.reversible hydrogen electrode(RHE).The partial current density of CO formed by Au@CB[6]increases dramatically,as 3.18 mA/cm2 at−0.6 V,which is more than ten times as that of oleylamine-coated Au NPs(Au@OAm,0.31 mA/cm2).Operando electrochemical measurement combined with density functional theory(DFT)calculations reveals that CB[6]can gather CO_(2)and lead the increased local CO_(2)concentration near metal interface,which realizes significantly enhanced electrochemical CO_(2)reduction reaction(CO_(2)RR)performance.

Hierarchically structured flower-like Ru nanoparticles-cucurbit[6]uril/multiwalled carbon nanotubes as efficient pH-universal hydrogen evolution electrocatalyst

Developing efficient and stable electrocatalyst to hydrogen evolution reaction adaptable for electrolytes with different p H is a big challenge.In this work,a hierarchically structured ternary nanohybrid composed of flower-like Ru nanoparticles,rigid macrocyclic cucurbit[6]uril(CB[6])and carboxylated multiwalled carbon nanotubes(MWCNTs)was successfully prepared by chemical wet method.Benefited by the structural merits of flower-like Ru nanoparticles exposed abundant active sites supported by the MWCNTs holding superior mass transport and electrons transfer ability as well as the existence of CB[6],the obtained catalyst exhibited outstanding HER activities with overpotentials of 27,37 and 70 m V at-10 m A/cm^(2) in alkaline,acidic,and neutral electrolytes,respectively.Under the same electrocatalytic operation conditions,the HER performance is comparable or superior to commercial Pt/C catalyst(47,27and 49 m V).Besides,chronopotentiometric and accelerated stability test also revealed its extraordinary stability,which could be further employed for electrocatalytic procedure in a broad pH range.

Replacing PVP by macrocycle cucurbit[6]uril to cap sub-5 nm Pd nanocubes as highly active and durable catalyst for ethanol electrooxidation

Pd nano cubes(NCs)en closed by six{100}facets are fasci nating model materials for both fun dame ntal studies and practical applicati ons.However,the only available method to prepare well-defined sub-10 nm Pd NCs was developed by Xia et al.more than 10 years ago,un avoidably using polyvinyl pyrrol id one(PVP)polymer to preve nt particle aggregati on.The strongly adsorbed PVP extremely deteriorates the catalysts*efficiency because of the high coverage of accessible surface-active sites.Numerous efforts have been devoted to replacing PVP with weaker capping agents but with limited progress predominately due to the difficulties in tuning the growth kinetics of Pd NCs.For the first time,we report that macrocycle cucurbit[6]uril(CB[6])can replace PVP in the synthesis of Pd NCs by dedicatedly controlling the growth parameters.CB[6]capped Pd NCs showed 1.1-1.5 times in creased specific surface area compared to the surfactant-free commercial Pd catalysts.Moreover,X-ray photoelectron spectroscopy dem on strated the modified electronic structure of Pd NCs through the carb onyl group of CB[6].Consequently,compared to the commercial catalysts,the obtained Pd NCs exhibited 7 times higher current density towards ethanol oxidation reaction.Remarkably,after 17 h of continuous work,it reduced deactivation by up to 1-4 orders of magnitude.

Facile ultrafine copper seed-mediated approach for fabricating quasi-two-dimensional palladium-copper bimetallic trigonal hierarchical nanoframes

Anisotropic Pd nanoparticles with highly branched morphologies are urgently needed as building blocks for nanoscale devices, catalysts, and sensing materials owing to their novel structures and unique physicochemical properties. However, realizing size control and branch manipulation for these materials is very challenging. In this study, we develop a facile ultrafine Cu seed-mediated approach in the aqueous phase to produce novel Pd-Cu trigonal hierarchical nanoframes （THNFs）. The main branch of most of the obtained nanocrystals is tripod-like, with advanced branches along the arms as frame units having self-similarity. In this method, the size of the Pd-Cu THNFs can be flexibly controlled by manipulating the nucleation involving the sub-3 nm Cu seeds. These Pd-Cu THNFs outperform Pd black with regard to their ethanol-oxidation performance, having a specific activity and mass activity 9.7 and 6.6 times higher, respectively. This research provides a versatile ultrafine seed-mediated approach for producing size-controlled anisotropic bimetallic nanoframes.