LiCl as Phase‐Transfer Catalysts to Synthesize Thin Co₂P Nanosheets for Oxygen Evolution Reaction

Abstract

Inorganic salts have been widely studied as templatesf or the synthesis of 2D layer structures. However,t heses alts normally can only serve as templates without any catalytic activity.H ere, we report that LiCl used for the synthesis of ultrathin nanosheets not only serves as template for the synthesis of ultrathin Co 2 Pn anosheets with at hickness of 0.7 nm but also acts as ac atalyst that induces the phase-transfer from CoP to Co 2 P. The Co 2 Pn anosheets have ah ighe lectrochemical performance for oxygen evolutionr eaction.Transition-metal phosphides (TMP) are an important class of functional materials with catalytic, photonic, semiconducting, electronic,a nd mechanical properties. [1] In recent years, extensive efforts have been devotedt os tudy nanostructured TMPs as noble-metal free electrocatalysts for the hydrogen evolution (HER) [2] and oxygen evolution reactions (OER). [3] Among TMPs, cobalt phosphides( CPs) have attracted attention as emerging electrocatalysts on both anode and cathode for overall water splitting because of their excellent electrocatalytic activities and high stabilityi nb oth acidic and basic media. [4] However, they are mainly obtained in the form of 0D (nanodots and fine nanoparticles), [5] 1D (nanowires), [6] and 3D (nanostructures and nanoarrays) [7] but rarely as 2D nanomaterials, especially with confined thickness. [8] This can be attributed to difficultb ondcleavage of non-layered CPs and lack of an intrinsic driving force for a2 Da nisotropic growth restraining the synthesis of atom-thick 2D nanosheets. [9] In principle, very thin CPs nanosheets have some unique characteristics:T heirn anometerrange thickness allows rapid mass transport and reduces the charge migration distance from the bulk to the surface whereas the high percentage of exposed surfacesl eads to an increasedn umber of unsaturated metal sites as active centers. [10] Therefore, the synthesis of CPs with 2D layer structures has become an urgent task of acquiring CP-based high-performance electrocatalysts.The phase-controlled synthesis of CPs is of particular importance, because their properties are not only relatedt ot heir morphology, [2c, 11] composition, [3b, 5b, 12] size, [13] and dimension [14] but also are phase dependent. [15] For example, Guo et al. developed ap hase-transfer method to synthesize the desired phase of CoO for electrochemical OER. [16] The product, which was synthesized by adding sodiumo leate during synthesis, showed ahigherwater oxidation activity than the Co 3 O 4 phase. In addition, Callejas et al. [17] reported that CoP nanoparticles showeda lower overpotential for HER than Co 2 Pn anoparticles. Interestingly,v ery thin Co 2 Pn anowires were reported that exhibited an enhanced electrocatalytic activityf or the oxygen evolution from water splitting compared to CoP nanowires. [18] The main reason is the high cobalt contenti nC o 2 P, which can generate more active sites. As such, the phasec ompositionp lays ac rucial role in improving electrocatalytic activity (HER or OER). The...

Tuning Crystallinity and Surface Hydrophobicity of a Cobalt Phosphide Cocatalyst to Boost CO2 Photoreduction Performance

“…The pristine CoP nanoparticles were synthesized according to a reported method with some modifications [20b,21] . In the typical synthesis, the obtained Co 3 O 4 nanoparticles (0.1 g) and NaH 2 PO 2 ⋅ H 2 O (mass ratio of 1 : 5) were mixed and ground evenly in a mortar.…”

“…: 29-0497). [21] Clearly, the crystallinity of CoP-600 is markedly higher than that of CoP by comparing the peak intensities of their XRD patterns. Moreover, results of Rietveld refinement based on the corresponding strongest diffraction peaks ( Figure S2) reveal that, as the post-treatment temperature increases, the crystalline grain of CoP grows gradually while the half peak width reduces in turn.…”

Ultrathin NiFeS Nanomeshes with Sulfur Vacancy for Electrocatalytic Hydrogen Evolution

“…The electronic and geometric structures of electrocatalysts determine their performance . The ultrathin two‐dimensional (2D) nanomaterials have exhibited outstanding performance as electrocatalysts due to the high surface‐to‐volume ratio and unique electronic structure . Furthermore, creating pores in nanosheets to construct nanomesh can increase the number of active sites and facilitate the diffusion of electrolyte .…”

Synthesis of Metal Phosphide Nanoparticles Supported on Porous N‐Doped Carbon Derived from Spirulina for Universal‐pH Hydrogen Evolution

“…The peaks at BE = 798.2 and 781.7 eV reflect the existence of oxidizedC os pecies, and those at BE = 803.5 and 786.1 eV are attributed to satellite peaks. [17] The fine spectrum of P2p ( Figure 3f)s hows ap eak at BE = 129.3 eV,w hich corresponds to the P2pi nC o 2 P. The other peaks at BE = 133.6 and 134.8 eV are assigned to PÀCa nd PÀO, respectively. [18] Remarkably,t he BE of Co 2p 3/2 (CoÀP) has ap ositive shiftc ompared to that of metallicC o( BE = 778.1 eV), and the BE of P2ph as an egative shift compared to that of elemental P( BE = 130 eV).…”