Oxygen reduction reaction on single Pt nanoparticle

Nanocollision electrochemistry is employed to evaluate the ORR’s activity of one single Pt nanoparticle,the effect of the size and ligand is investigated.The size-normalized activity of the Pt nanoparticle of 4 nm is two times higher than that of 25 nm,confirming that the intrinsic activity does depend on the size of the nanoparticles.It is further found that the adsorbed ligand does yield effect on electrocatalysis,and the adsorption strength follows the order of PVP>CTAB>citrate.This work is of significance to understand the nature of the ORR’s electrocatalysis at the level of an individual entity,which makes the structure-activity correlation in a more reliable way.

Achieving Negatively Charged Pt Single Atoms on Amorphous Ni(OH)_(2)Nanosheets with Promoted Hydrogen Absorption in Hydrogen Evolution

Single-atom(SA)catalysts with nearly 100%atom utilization have been widely employed in electrolysis for decades,due to the outperforming catalytic activity and selectivity.However,most of the reported SA catalysts are fixed through the strong bonding between the dispersed single metallic atoms with nonmetallic atoms of the substrates,which greatly limits the controllable regulation of electrocatalytic activity of SA catalysts.In this work,Pt-Ni bonded Pt SA catalyst with adjustable electronic states was successfully constructed through a controllable electrochemical reduction on the coordination unsaturated amorphous Ni(OH)_(2)nanosheet arrays.Based on the X-ray absorption fine structure analysis and first-principles calculations,Pt SA was bonded with Ni sites of amorphous Ni(OH)_(2),rather than conventional O sites,resulting in negatively charged Pt^(δ-).In situ Raman spectroscopy revealed that the changed configuration and electronic states greatly enhanced absorbability for activated hydrogen atoms,which were the essential intermediate for alkaline hydrogen evolution reaction.The hydrogen spillover process was revealed from amorphous Ni(OH)_(2)that effectively cleave the H-O-H bond of H_(2)O and produce H atom to the Pt SA sites,leading to a low overpotential of 48 mV in alkaline electrolyte at-1000 mA cm^(-2)mg^(-1)_(Pt),evidently better than commercial Pt/C catalysts.This work provided new strategy for the control-lable modulation of the local structure of SA catalysts and the systematic regulation of the electronic states.

Improved Plasmonic Hot‑Electron Capture in Au Nanoparticle/Polymeric Carbon Nitride by Pt Single Atoms for Broad‑Spectrum Photocatalytic H_(2)Evolution

ABSTRACT Rationally designing broad-spectrum photocatalysts to harvest whole visible-light region photons and enhance solar energy conversion is a“holy grail”for researchers,but is still a challenging issue.Herein,based on the common polymeric carbon nitride(PCN),a hybrid co-catalysts system comprising plasmonic Au nanoparticles(NPs)and atomically dispersed Pt single atoms(PtSAs)with different functions was constructed to address this challenge.For the dual co-catalysts decorated PCN(PtSAs–Au_(2.5)/PCN),the PCN is photoexcited to generate electrons under UV and short-wavelength visible light,and the synergetic Au NPs and PtSAs not only accelerate charge separation and transfer though Schottky junctions and metal-support bond but also act as the co-catalysts for H_(2) evolution.Furthermore,the Au NPs absorb long-wavelength visible light owing to its localized surface plasmon resonance,and the adjacent PtSAs trap the plasmonic hot-electrons for H_(2) evolution via direct electron transfer effect.Consequently,the PtSAs–Au_(2.5)/PCN exhibits excellent broad-spectrum photocatalytic H_(2) evolution activity with the H_(2) evolution rate of 8.8 mmol g^(−1) h^(−1) at 420 nm and 264μmol g^(−1) h^(−1) at 550 nm,much higher than that of Au_(2.5)/PCN and PtSAs–PCN,respectively.This work provides a new strategy to design broad-spectrum photocatalysts for energy conversion reaction.

Single-atom Pt promoted Mo_(2)C for electrochemical hydrogen evolution reaction

Hydrogen generation from electrochemical water splitting powered by renewable energy is important to the sustainable society,but the prohibitive cost of current Pt electrocatalyst has impeded the large-scale production of hydrogen by water electrolysis.In this contribution,a new low-Pt electrocatalyst for hydrogen evolution reaction(HER) has been fabricated by a facile one-pot synthesis approach,in which Pt^(2+)cations and phosphomolybdic acid confined in the metal-organic frameworks(MOFs) were submitted to pyrolysis to yield Pt single atoms dispersed into Mo_(2)C nanocrystals in 3 D porous carbon matrix.The as-synthesized Pt_(1)-Mo_(2)C-C catalyst with Pt content of only 0.7 wt% exhibited remarkably enhanced activity for HER in 1 M KOH,with overpotential at 10 mA/cm^(2) lowered from 211 mV to 155 mV and 7-fold higher mass activity(7.14 A/mgpt) than the benchmark 20 wt% Pt/C.The promoted activity can be attributed to the electronic interaction between Pt single atoms and Mo2C surface,which not only improved water activation but also strengthened hydrogen adsorption,as indicated by FTIR and microcalorimetric characterizations.

Single-atomic Pt sites anchored on defective Ti0_(2) nanosheets as a superior photocatalyst for hydrogen evolution

Single-atomic site catalysts have drawn considerable attention because of their maximum atom-utilization efficiency and excellent catalytic activity.In this work,a highly active single-atomic Pt site photocatalyst was synthesized through employing defective Ti0_(2) nanosheets as solid support for photo-catalytic water splitting.It indicated that the surface oxygen vacancies on defective Ti0_(2) nanosheets could effectively stabilize the single-atomic Pt sites through constructing a three-center Ti-Pt-Ti structure.The Ti-Pt-Ti structure can hold the stability of isolated single-atomic Pt sites and facilitate the separation and transfer of photoinduced charge carriers,thereby greatly improving the photocatalytic H2 evolution.Notably,our synthesized photocatalyst exhibited a remarkably enhanced H2 evolution performance,and the H2 production rate is up to 13460.7μmol h^(-1)·g^(-1),which is up to around 29.0 and 4.7 times higher than those of Ti0_(2) nanosheets and Pt nanoparticles-Ti0_(2).In addition,a plausible enhanced reaction mechanism was also proposed combining with photo-electrochemical characterizations and density functional theoiy(DFT)calculation results.Ultimately,it is believed that this work highlights the benefits of a single-site catalyst and paves the way to rationally design the highly active and stable single-atomic site photocatalysts on metal oxide support.

A DFT study on Pt single atom loaded COF for efficient photocatalytic CO_(2)reduction

Photocatalytic CO_(2)reduction provides a promising strategy for the alleviation of greenhouse effect and energy shortage problem.Metal single atom modification is an effective method to improve the CO_(2)reduction performance of covalent organic framework(COF)photocatalysts,while the intrinsic mechanism is not revealed in depth.Herein,a Pt-COF photocatalytic system was constructed by embedding Pt single atom in TFPT-TMT-COF(TFPT:1,3,5-tris(4-formylphenyl)-triazine,TMT:2,4,6-trimethyl-1,3,5-triazine).Based on density functional theory(DFT)calculation,the geometric structure and electronic property of Pt-COF were investigated,and the CO_(2)adsorption and reduction reaction process on Pt-COF were simulated.The results show that the Pt atom can be steadily anchored in COF via the formation of Pt-N and Pt-C bonds.Moreover,there is strong electronic interaction between Pt and COF.The incorporation of Pt atom benefits the CO_(2)reduction activity of COF from multiple aspects:(ⅰ)reducing the band gap and improving light absorption;(ⅱ)enhancing CO_(2)adsorption and activating the CO_(2)molecule;(ⅲ)decreasing the energy barrier in the hydrogenation step of CO_(2)→COOH,thus facilitating CO_(2)conversion to CO;(ⅳ)inhibiting the hydrogenation of CO,thereby increasing the selectivity of CO.This work brings a novel insight into the excellent CO_(2)reduction performance of Pt modified COF,and provides useful references for the design of single atom photocatalysts.

In Situ High-Temperature Reaction-Induced Local Structural Dynamic Evolution of Single-Atom Pt on Oxide Support

The dynamic evolution of active site coordination structure during a high-temperature reaction is critically significant but often difficult for the research of efficient single-atom catalysts(SACs).Herein,we for the first time report the in situ activation behaviors of the local coordination structure of Pt single atoms(Pt_(1))during the high-temperature oxidation of light alkanes.The distinctly enhanced activity of the catalyst is attributed to the in situ evolved Pt_(1)−oxygen vacancy(Pt_(1)−OV)combination ensemble as an efficient and stable active site.Theoretical calculations reveal that the lattice oxygen adjacent to Pt_(1)and the H dissociated from CH4 constitute the lattice hydroxyl,which is the initial step in the formation of the Pt_(1)−OV combination.Pt_(1)and nearby unsaturated Mn can donate the charge back to O−O to promote the dissociation of O_(2).This work provides molecular-level insight into the in situ reaction-induced evolution of a single-atom coordination environment for designing efficient SACs under harsh conditions.

Atomic Pt anchored on hierarchically porous monolithic carbon nanowires as high-performance catalyst for liquid hydrogenation

Monolithic catalysts play a crucial role in various catalytic applications,e.g.,chemical synthesis,energy conversion,and environmental treatment,but their catalytic efficiency is often limited by the restricted mass transfer and insufficient exposure of active sites.Herein,we present a dual-templating strategy to fabricate atomic Pt dispersed on monolithic N-doped mesoporous carbon nanowires(Pt_(1)/NMCW)with abundant super-/macropores,which,as monolithic catalyst,exhibits high catalytic performance in hydrogenation of 4-nitrophenol(4-NP).During synthesis,triblock copolymer(Pluronic F127)is employed as a primary soft template to generate the mesoporous structured carbon nanowires to improve the accessibility of Pt single sites;KCl crystallite is used as a secondary hard template to create the super-/macropores,which are beneficial for enhancing the mass transfer efficiency.Thanks to the dual-templating strategy that creates the monolithic carbon nanowires with hierarchically porous structure,the obtained Pt_(1)/NMCW shows highly enhanced catalytic activity in 4-NP hydrogenation,outperforming its analogue synthesized without using KCl as template and being comparable to the nano-powder catalyst(i.e.,atomic Pt loaded on the Ndoped carbon nanospheres,Pt_(1)/NCS).

1T-phase MoS_(2)edge-anchored Pt_(1)-S_(3)active site boosting selective hydrogenation of biomass-derived maleic anhydride

Selective hydrogenation of biomass-derived maleic anhydride(MAH)to succinic anhydride(SA)is valuable but remains a challenge due to the complicated reaction network.We here report that single Pt atoms decorated onto the edges of two-dimensional(2D)1Tphase MoS_(2)(Pt1/1T-MOS_(2)SAC)as a proof-of-concept catalyst can efficiently convert biomass-derived MAH to SA with 100%conversion and 100%selectivity under mild conditions.The kinetic data and characterization results suggest that the catalytic performance of the edge-anchored Pt1/1T-MoS_(2)SAC originates from the facile H_(2)dissociation induced by the electron-deficient Pt1atoms and the pocket-like configuration of Pt1active site confines the adsorption configuration of MAH by the steric effect.The strategy of fabricating edge-confined catalysts offers a new direction to design novel SACs for biomass-derived transformations.

Studies of surface processes of electrocatalytic reduction of CO_(2) on Pt(210), Pt(310) and Pt(510)

Surface processes of CO_(2)reduction on Pt(210),Pt(310),and Pt(510)electrodes were studied by cyclic voltammetry.Different surface structures of these platinum single crystal electrodes were obtained by various treatment conditions.The experimental results illustrated that the electrocatalytic activity of Pt single crystal electrodes towards CO_(2)reduction is decreased in an order of Pt(210)>Pt(310)>Pt(510),i.e.,with the decrease of(110)step density on well-defined surfaces.When the surfaces were reconstructed due to oxygen adsorption,the catalytic activity of all the three electrodes has been enhanced to a cer-tain extent.Although the activity order remains unchanged,the electrocatalytic activity has been en-hanced more significantly as the density of(110)step sites is more intensive on the Pt single crystal surface.It has revealed that the more open the surface structure is,the more active the Pt single crystal electrode will be,and the easier for the electrode to be transformed into a surface structure that exhib-its higher activity under external inductions.However,the relatively ordered surfaces of Pt single crystal electrode are comparatively stable under the same external inductions.The present study has gained knowledge on the interaction between CO_(2)and Pt single crystal electrode surfaces at a micro-scopic level,and thrown new insight into understanding the surface processes of electrocatalytic re-duction of CO_(2).