Hierarchical Porous Molybdenum Carbide Based Nanomaterials for Electrocatalytic Hydrogen Production

Abstract

The electrocatalytic hydrogen evolution reaction (HER) for the preparation of hydrogen fuel is a very promising technology to solve the shortage of hydrogen storage. However, in practical applications, HER catalysts with excellent performance and moderate price are very rare. Molybdenum carbide (Mo x C) has attracted extensive attention due to its electronic structure and natural abundance. Here, a comprehensive review of the preparation and performance control of hierarchical porous molybdenum carbide (HP-Mo x C) based catalysts is summarized. The methods for preparing hierarchical porous materials and the regulation of their HER performance are mainly described. Briefly, the HP-Mo x C based catalysts were prepared by template method, morphology-conserved transformations method, and secondary conversion method of an organic-inorganic hybrid material. The intrinsic HER kinetics are enhanced by the introduction of a carbon-based support, heteroatom doping, and the construction of a heterostructure. Finally, the future development of HP-Mo x C based catalysts is prospected in this review.

Review and Perspective on Transition Metal Electrocatalysts Toward Carbon-Neutral Energy

“…The high cost and scarcity of these rare metals, however, make it impractical for large-scale application. Pt/C is frequently used to benchmark the performance of other catalysts–it exhibits low overpotentials of 28 and 43 mV with corresponding Tafel slopes of 30 and 125 mV/dec in acidic and basic electrolytes, respectively. − This indicates a Tafel rate determining step in acidic media and a Volmer rate determining step in basic media. Table shows the HER activities of selected noble-based and transition metal-based electrocatalysts …”

Smart Designs of Mo Based Electrocatalysts for Hydrogen Evolution Reaction

“…For example, Mo 2 C nanosheets doped with N were synthesized via chemical vapor reduction with dicyandiamide as the N source [123]. Based on the characteristic peaks of Mo 2+ at 231.6 and 228.6 eV (Mo 3d spectra) and pyridinic N at 398.5 eV (N 1s spectra), the successful introduction of N and the electron rich environment surrounding Mo were proven [4]. Benefiting from the lone pairs of N atoms, the adsorption of active H was promoted and electronic conductivity was enhanced with an increased spin density and electron density [125].…”

“…Considering the environmental pollution and greenhouse effect caused by the excessive utilization of fossil fuels, the exploitation of renewable and clean energy sources is imminent and imperative in order to realize the sustainable development of industries and economies [1,2]. Characterized by a carbon free nature, green product (H 2 O) and high energy density, hydrogen has been regarded as a promising alternative to conventional fossil fuels, prior to other renewable energies (e.g., wind and solar energy) that suffer from an intermittent nature and low energy density [3,4]. Thus far, general routes of producing hydrogen include the gasification of coal and biomass, conversion of hydrocarbons (e.g., methane and tar molecules) and electrolytic water splitting [2].…”

“…To address the issues, various modifications have been developed to improve the catalytic performances of Mo based materials, such as combination with carbon matrix, doping with heteroatoms and construction of heterostructures [24][25][26][27]. So far, most of the reviews are focused on specific Mo based compounds; a comprehensive review based on the modification strategies of Mo based electrocatalysts rather than the materials is rarely reported in HER [1][2][3][4][5]. Therefore, in this review, in addition to the introduction of the reaction mechanism, all the types of Mo based materials used in HER will be summarized.…”

Molybdenum Carbide-Reduced Graphene Oxide Composites as Electrocatalysts for Hydrogen Evolution

“…However, Mo 2 C nanoparticles have some drawbacks, such as easy agglomeration into large particles, which may result in the slow transport of electrons and protons during HER, fewer available active sites due to larger particles size, and relatively poor conductivity compared to the noble metal nanoparticles, hence leading to poor electrocatalytic activity . Several synthetic and nanostructuring approaches have been developed for an advanced electrocatalyst architecture to achieve the full potential of Mo 2 C as an affordable and efficient electrocatalyst. , These include facile one-step and two-step synthesis methods for highly porous Mo 2 C structures, , nanostructuring, , elemental doping, , and hybrid nanostructures. Despite all these efforts, it still remains a challenge to achieve the desired Mo 2 C nanoarchitecture.…”