MoP/Mo₂C@C: A New Combination of Electrocatalysts for Highly Efficient Hydrogen Evolution over the Entire pH Range

Abstract

During the exploration of highly efficient noble-metal-free electrocatalysts for the hydrogen evolution reaction (HER), a promising and challenging strategy is to fabricate composite nanocatalysts by finely tuning metal and/or nonmetal element components. Herein, we report a new HER electrocatalyst, which is composed of molybdenum phosphide and molybdenum carbide composite nanoparticles (NPs) coated by few-layer N-doped graphitic carbon shells (denoted as MoP/MoC@C). Such a new combination mode of electrocatalysts is realized by a one-step annealing route with the mixture of a Mo/P-based polyoxometalate (POM) and dicyandiamide. On the basis of this method, the simultaneous phosphorization and carbonization in a nanoscale confined space can be easily achieved by the use of POM as the molecular-element-regulating platform. MoP/MoC@C exhibits more remarkable HER performance over the whole pH range than those of MoP, MoC, and the physical mixture of MoP and MoC. The low overpotentials of 89, 136, and 75 mV were obtained at a current density of 10 mA cm in the media of pH = 0, 7, and 14, respectively. Furthermore, MoP/MoC@C shows a long-term durability for 14 h over the entire pH range (0-14). Because of the protection of carbon shells, such composite electrocatalyst also possesses better transition-metal tolerance exemplified by Fe, Co, and Ni than that of 20% commercial Pt/C. This work demonstrates the advantage of POM precursors in adjusting the component and properties of nanoscale composite electrocatalysts for HER, which may suggest new options for the fabrication of highly efficient composite electrocatalysts.

N,P-Codoped Carbon Layer Coupled with MoP Nanoparticles as an Efficient Electrocatalyst for Hydrogen Evolution Reaction

“…Typically, the Mo 3d peak can be fitted with four regions in Figure 2c, indicating that there were two valence states (+4, +6) for the Mo element in the MoP/NPCs, which confirms the existence of MoP [27]. The high oxidation state of Mo 4+ (228.2 and 231.6 eV) and Mo 6+ (233.2 and 236.3 eV) in MoP/NPCs may be caused by the surface oxidation suffering from air contact [32]. For the high-resolution N 1s spectrum in Figure 2d, three peaks at 398.2 eV, 399.2 eV, and 401.5 eV were assigned to pyridinic N, pyrrolic N, and graphitic N, which was ascribed to the heteroatom N-doping in the graphitic carbon [37].…”

“…The prepared catalyst was mainly composed of C, Mo, P, O, and N (Figure 1c–g, Figure S5). The relatively uniform dispersion could expose abundant active sites and rich channels for the diffusion of electrolytes, which is beneficial for the catalytic process [32,33]. As observed from Figure 1i, a high-resolution transmission electron microscopy (HRTEM) image of a MoP/NPC exhibited that the catalysts were coated by graphitic carbon shells, and the lattice plane distance of MoP was 0.27 nm, which can be ascribed to the lattice plane (101) of MoP [32].…”

“…As depicted in Figure 2f, the peaks located at 27.81°, 32.03°, 43.06°, 57.47°, 57.81°, 64.85°, 67.03°, 67.52°, and 74.21° indexed to (001), (100), (101), (110), (002), (111), (200), (102), and (201) facets of pure MoP (JCPDS, No. 24-0771), respectively [32]. …”

Network‐Like Ni1−xMox Nanosheets: Multi‐Functional Electrodes for Overall Water Splitting and Supercapacitor

“…The charge transfer resistance (R ct ) at the interface between the electrolyte and electrode corresponds to the semicircle. [61] We further investigated the OER properties of Ni 1À x Mo x /CC in 1 M KOH (Figure 4c). In addition, electrochemical double-layer capacitances ( Figure S6a) were acquired via CV measurements (Figure S6 bf).…”

Surface engineering-modulated porous N-doped rod-like molybdenum phosphide catalysts: towards high activity and stability for hydrogen evolution reaction over a wide pH range

“…[12][13][14][15][16][17][18] Wherein, a kind of ternary pyrite-type CoPS has been fabricated and act as a high-performance Earth-abundant catalyst for electrochemical hydrogen production with lower catalytic overpotential and outstanding long-term operational stability. 19 Among different metal-based compounds, Mo-based catalytic materials, such as MoS 2 28 and MoP, [29][30][31] which are considered as promising candidates for hydrogen production owing to their low cost and high catalytic activities. Among them, MoP has attracted special attention because of its high electrical conductivity, adjustable morphology, structure and surface architecture.…”