Carbon‐Tailored Semimetal MoP as an Efficient Hydrogen Evolution Electrocatalyst in Both Alkaline and Acid Media

Abstract

to conventional energy sources due to its clean nature (i.e., only water is produced upon burning) and high energy density. [2] The electrochemical splitting of water to yield high purity hydrogen (>99.6%) has therefore drawn increasing attention. [3] However, due to the sluggish kinetics of the HER, the use of electrocatalysts is essential in order to reduce the overpotential, especially in alkaline solutions. Although Pt and Pt-based alloys are still benchmark electrocatalysts in the HER, the high cost and low abundance of Pt limits its widespread application in hydrogen production technologies.Recently, a range of abundant transition metal phosphides such as molybdenum phosphide have been intensively examined as potential HER electrocatalysts. Various strategies have been employed to improve the electrocatalytic HER activity of transition metal phosphides, including surface phosphosulfidation, hybridization, and elemental doping. [4] However, despite such modifications, MoP continues to suffer from a high overpotential (>130 mV at 10 mA cm −2 ) [5] and significant instability in alkaline electrolytes. Here we investigate whether the topological states of MoPThe electrolysis processes such as hydrogen evolution reaction (HER) require high efficient catalysts with robust surface stability. A high conductivity is also necessary to speed up the charge transport between the catalyst and the electrolyte. Recently, the observation of exceedingly high conductivity in the topological semimetal MoP, has provided a model catalyst to investigate the correlation between the electrical transport and the electrocatalytic activity for the HER. Thus, MoP is encapsulated in a Mo, P codoped carbon layer (MoP@C). This composite material exhibits outstanding HER performance, with an extremely low overpotential of 49 mV at a current density of 10 mA cm −2 and a Tafel slope of 54 mV dec −1 in an alkaline medium. In addition, electron transport analysis indicates that MoP exhibits high conductivity and mobility due to the existence of triple-point fermions and a complex Fermi surface. Furthermore, the presence of PC and MoC bonds at the interface between the carbon layer and the MoP particles modulates the band structure of MoP@C and facilitates fast electron transfer, accumulation, and subsequent delocalization, which are in turn responsible for the excellent HER activity.

Synergistically Interactive Pyridinic‐N–MoP Sites: Identified Active Centers for Enhanced Hydrogen Evolution in Alkaline Solution

“…The XPS spectra of Mo 3d and P 2p were recorded to determine the charge states and electronic structures of MoP in MoP@NCHSs‐T (Figure d). In the Mo 3d spectra for bulk MoP, deconvolution of the spectra gives two doublets at 232.1 eV/228.5 eV (MoO 2 , 3d 3/2 /3d 5/2 ) and 235.0 eV/231.9 eV (MoO 3 , 3d 3/2 /3d 5/2 ), respectively . Two other peaks at lower binding energy (228.1/231.2 eV) are assigned to molybdenum phosphide .…”

Hierarchical MoP Hollow Nanospheres Anchored on a N,P,S‐Doped Porous Carbon Matrix as Efficient Electrocatalysts for the Hydrogen Evolution Reaction

“…In addition, the XRD peaks of MoP 2 O 7 can be also detected in the samples obtained without petroleum asphalt. These results indicate that petroleum asphalt and g‐C 3 N 4 exert critical reducing effects for the formation of MoP, which avoids use of additional reductants like H 2 in previous reports …”

“…These results indicate that petroleum asphalta nd g-C 3 N 4 exert critical reducing effects for the formation of MoP,w hich avoids use of additional reductants like H 2 in previous reports. [23,47] To study the influenceo fM os alt content on the morphology and electrocatalytic behavior of the products,f ive samples with different amounts of Mo salts were prepared for comparison. As shown in Figure 1c,a ll as-obtained samples exhibit apparentc haracteristicp eaks of MoP.F urthermore,n oc lear XRD features of other oxidation states of Mo are observed,r evealing the high purity of the MoP phase.…”

Partially exposed RuP 2 surface in hybrid structure endows its bifunctionality for hydrazine oxidation and hydrogen evolution catalysis

“…2D mainly contains four peaks situated at 398.4 eV (pyridinic N), 400.6 eV (pyrrolic N), 401.8 eV (graphitic N), and 404 eV (oxygenated N), respectively; among those, the high content of graphitic N (39 atomic %) could be favorable for the electrocatalytic activity through modulating the electronic structure (27). The XPS results imply that the unique hybrid structure of partially exposed RuP 2 in the carbon matrix may induce the interfacial charge transfer from Ru to P and then to coupled C (22) and thus may modulate the Ru and C simultaneously, which could further improve the bifunctional performance for HzOR and HER.…”