A Review of Phosphide‐Based Materials for Electrocatalytic Hydrogen Evolution

Abstract

for HER when nanoscale MoS 2 is used, [ 1 ] albeit bulk MoS 2 is suggested to be inactive towards HER. [ 2 ] Thus most studies have focused on designing thin layered/nanostructured MoS 2 nanomaterials with most exposed edges for HER. To this end, amorphous MoS 2,[ 3 ] MoS x nanosheets [ 4 ] were found to outperform bulk MoS 2 signifi cantly; layer-dependent attributes, [ 5 ] the correlation with intrinsic low conductivity out-of-plane, and phasedetermined performance have also been studied. [ 6 ] These fi ndings have stimulated the work of sulfi de of earth-abundant metals, e.g., WS 2 [ 7 ] and its analogues, selenides, [ 8 ] resulting in a big family of chalcogenides of fi rst-row transition metals. [ 9 ] Reviews [ 6b , 7c , 10 ] have been conducted from different perspectives and can be referred to accordingly. Unfortunately, the best performing MoS 2 catalyst still lacks the competitiveness of Pt. Furthermore, improvements in performance relies heavily on the basis that moly bdenum/tungsten chalcogenides (sulfi de, selenide) are nanostructured with abundant S-edges and are thin layered (preferable single layer). These requirements may severely constrain their application in large-scale production. Thus, it is imperative to continue the search for new inexpensive catalysts that can rival the performance of Pt while being suitable for large-scale hydrogen production.It was only recently discovered that hydrogen evolution proceeds via a similar pathway to that of hydrogenation (hydrotreating process), e.g., hydrodesulfurization (HDS), where a reversible ad/desorption of hydrogen on catalyst is critical for achieving fast kinetics. This correlation broadens the scope of search for new catalysts. Hence, phosphides, previously employed as catalysts for HDS, were found to be active towards HER, e.g., Ni 2 P [ 11 ] has been reported to achieve a better performance than the state-of-the-art MoS 2 .[ 11c ] This pivotal work [ 11c ] was followed by a variety of studies applying phosphide as catalysts for HER. This class of electrocatalyst with superb electrocatalytic activities has thus opened up a new avenue in the search of non-noble metal catalysts for HER. Here, we focus our discussion on the recent developments of synthesis methodology of phosphides for HER. Based on different synthetic routes of phosphides, we then make a comparative survey of their activities, which are evaluated in terms of experimental metrics of over-potential ( η ) at a certain current density ( j ), Tafel slope coupled with exchange current density ( j o ) extrapolated from the plot of η vs. Log 10 ( j ), and turnover frequency (TOF). In conjunction with experimental results, Hydrogen evolution by means of electrocatalytic water-splitting is pivotal for effi cient and economical production of hydrogen, which relies on the development of inexpensive, highly active catalysts. In addition to sulfi des, the search for non-noble metal catalysts has been mainly directed at phosphides due to the superb activity of phosphides for hydrogen ev...

Nanoporous Gold Surface: An Efficient Platform for Hydrogen Evolution Reaction at Very Low Overpotential

“…For example, cobalt, [11][12][13] nickel, 14 copper [15][16][17] bimetallic catalyst, 18 transition metal carbide nanocrystals M3C (M: Fe, Co, Ni) encapsulated with vertically aligned graphene nanoribbons, 19 nitrogen and sulfur co-doped nanoporous graphene, 20 molybdenum sulfide (MoS 2 ), phosphide, carbon and noble metal-free catalysts are reported for the HER process. [21][22][23][24] Currently, nanoporous gold films (NPGF) have attracted attention for their widespread application in catalysis and in the sensors field because of their higher surface area in comparison to bulk gold electrodes, allowing superior electron transfer rate between the electrode-electrolyte interface. 25,26 Such platforms have been mainly prepared by alloying/dealloying or template methods, where hazardous chemicals are mostly used.…”

Ru-Doped Platelet-Like Ni2P Nanostructure for Electrocatalytic HER and ORR Applications

“…Due to its particular platelet-like structure, the as-synthesized Ru-doped Ni 2 P catalyst not only exhibits a remarkably enhanced electrocatalytic hydrogen evolution reaction (HER) performances with an onset potential of 35 mV, tafel slope of 34 mV dec -1 and long-term stability, but also possesses superior oxygen evolution reaction (OER) properties with an onset potential of 1.54 V and robust durability, exceeding the performance of an individual Ru or Ni 2 P component and comparable to that of commercial 20% Pt/C, IrO 2 catalysts. As confirmed by HRTEM, line-scan, elemental-mapping and electrochemical analysis, the superior electrocatalytic bifunctionality of Rudoped Ni 2 P nanostructure can be attributed to the combined influence of the following factors: (1) The good intrinsic electrocatalytic properties for the exposed abundant (001) planet of Ni 2 P [1][2][3][4] ; (2) The special platelet-like structure ensures larger specific surface area compared to simple flat or hollow nanosheets, along with more accessible active sites caused by defects, facilitating their electrocatalytic process; (3) The introduced metallic Ru enables faster electron transfer rate of semiconductor Ni 2 P and moderate hydrogen adsorption energy, and thus are responsible for their remarkable electrocatalytic bifunctionality [5], [6] . In summary, such platelet-like Ru-doped Ni 2 P nanostrufcture is expected to serve as a new kind of robust catalyst for HER and OER applications.…”

Perspective—Commercializing Lithium Sulfur Batteries: Are We Doing the Right Research?

“…At this level of analysis, the results are similar to those reported previously. 31 60 review articles examined overall Li-S research and suggested areas for investigation. The direction for research recommended by the most recent 34, covering all review articles published between 2014 and 2017, was synthesized in Figure 1 as 'recommended areas'.…”