Investigation of the Support Effect in Atomically Dispersed Pt on WO_3−x for Utilization of Pt in the Hydrogen Evolution Reaction

Abstract

Single-atom catalysts (SACs) have attracted growing attention because they maximizet he number of active sites, with unpredictable catalytic activity.Despite numerous studies on SACs,t here is little researcho nt he support, which is essential to understanding SAC. Herein, we systematically investigated the influence of the support on the performance of the SACb yc omparing with single-atom Pt supported on carbon (Pt SA/C) and Pt nanoparticles supported on WO 3Àx (Pt NP/WO 3Àx ). The results revealed that the support effect was maximized for atomically dispersed Pt supported on WO 3Àx (Pt SA/WO 3Àx ). The Pt SA/WO 3Àx exhibited ahigher degree of hydrogen spillover from Pt atoms to WO 3Àx at the interface, compared with Pt NP/WO 3Àx ,w hichd rastically enhanced Pt mass activity for hydrogen evolution (up to 10 times). This strategy provides an ew framework for enhancing catalytic activity for HER, by reducing noble metal usage in the field of SACs.Hydrogen is being pursued as af uture alternative to fossil fuels and an ideal energy carrier for renewable energy, because it has the highest energy density per mass without any pollutants.Currently,hydrogen production is primarily based on the steam reforming of fossil fuels,w hich is accompanied by environmental issues,s uch as as ubstantial increase in atmospheric CO 2 .Accordingly,itisnecessary to find sustainable and clean alternatives. [1] Electrochemical water splitting is considered ap otentially cost-effective and promising approach for clean hydrogen production. [2] Fort he cathodic hydrogen evolution reaction (HER), platinum (Pt)-based materials are known to the most active electrocatalysts,b ut the high cost and scarcity of Pt are key obstacles to commercial applications of water electrolyzers. [3] Hitherto,n umerous design strategies have been developed for nanostructured electrocatalysts to obtain outstanding electrochemical performance. [4] These strategies are shown to improve the utilization of Pt, and thereby to reduce the use of Pt. Fore xamples,c ore-shell [5] and hollow structures [6] can significantly improve Pt utilization by diminishing the buried non-active Pt atoms inside the particles. From this point of view,single-atom catalysts (SACs), where all metal species are individually dispersed on ad esired support, could be the best candidates to meet this goal, because they offer the maximum number of surface exposed Pt atoms.S everal studies have also demonstrated that Pt SACs show greatly boosted Pt mass activity compared to commercial Pt/C.However,research that considers the effect of the support on SACs performance for the HER is rarely found. [3,7] Thec hoice of support material is one of the most promising strategies for improving (electro)catalysis because interactions between the metal and support can drastically tune the electronic structure of the supported metal, and enhance performance. [8] Furthermore,i th as been recently reported that HER performance can be improved by not only changing the electronic structure of the supported m...

Hydrogen migration at restructuring palladium–silver oxide boundaries dramatically enhances reduction rate of silver oxide

“…The intermixing of palladium and silver occurs during the reduction of oxidized Ag(111) by molecular hydrogen due to the presence of PdO x islands. Previously, migration of hydrogen atoms has been demonstrated away from single metal atoms and metal islands to either a metal or metal oxide host; [19][20][21][22][23][38][39][40][41]63 however, intermixing and reconstruction during reaction was not evident. For example, single palladium atoms in copper promote molecular hydrogen dissociation on palladium and subsequent migration to the copper 38 .…”

“…Prior studies have demonstrated that the interface between metal nanoparticles and the metal oxide support can affect chemical behavior by the creation of specific active sites [12][13][14][15][16][17][18] and direct migration or "spillover" 19 of reactive species created on one phase to a neighboring phase of differing reactivity [19][20][21][22][23][24][25] . The metal/oxide support interface can significantly restructure in reactive gas environments on a short timescale of minutes and long length scales of microns 26 .…”

Hydrogen Evolution Reaction-From Single Crystal to Single Atom Catalysts

“…Hydrogen atom spillover (not to be confused with H 2 spillover, which includes dissociation and is an important step for hydrogenation reactions and hydrogen storage) was recognized as the phenomenon responsible for the promotion of Pt electrocatalytic activity towards the hydrogen evolution 47 years ago, for Pt supported on pyrolytic graphite [157]. Several experimental works contributed to the affirmation of H ads spillover as the important step in HER mechanism at Pt/C [158], Pt/transition-metal-oxide [159], Pt/Au [160], Pi/Ni [161], atomically-dispersed-Pt/WO 3-x [162], Pd/Au [163], WO 3 •2H 2 O/WS 2 [164], Rh/MoS 2 [165], Rh/Si (although authors do not employ the term spillover) [166], Pd@Cu(II) phthalocyanine/MOF [82], and Ni/rGO interfaces [70,167,168]. Kinetic Monte-Carlo simulations were employed to investigate the impact of the spillover rate on the rate of H 2 production at the Ni/rGO interface, using the model that was able to qualitatively reproduce the experimentally observed trends [168].…”

Hydrogen Evolution Reaction - From Single Crystal to Single Atom Catalysts

“…Hydrogen atom spillover (not to be confused with H2 spillover, which includes dissociation and is an important step for hydrogenation reactions and hydrogen storage) was recognized as phenomenon responsible for the promotion of Pt electrocatalytic activity towards the hydrogen evolution 47 years ago, for Pt supported on pyrolytic graphite [144]. Several experimental works contributed to the affirmation of Hads spillover as the important step in HER mechanism at Pt/C [145], Pt/transition-metal-oxide [146], Pt/Au [147], Pi/Ni [148], atomically-dispersed-Pt/WO3-x [149], Pd/Au [150], WO3·2H2O/WS2 [151], Rh/MoS2 [152], Rh/Si (although authors do not employ the term spillover) [153], Pd@Cu(II) phthalocyanine/MOF [69], and Ni/rGO interfaces [154,155]. Kinetic Monte-Carlo simulations were employed to investigate the impact of spillover rate on the rate of H2 production at Ni/rGO interface, using the model that was able to qualitatively reproduce the experimentally observed trends [155].…”