A Unified Theory for H₂ Evolution on Mo-Based Electrocatalysts

Abstract

Mo-based catalysts constitute a significant portion of active non-noble H 2 evolution reaction (HER) catalysts, but the role of Mo in conferring this activity remains debated. In this study, we utilize electrochemical, physical, functional, and computational approaches on a range of Mobased catalysts to derive a unified explanation for Mo HER catalyst function. Across all catalysts studied, the formation of Mo 3+ at cathodic potentials close to the thermodynamic HER onset drives activity, and activity between catalysts is therefore heavily determined by the ease of reduction from Mo 4+ to Mo 3+ . As such, surface oxidation is detrimental to HER activity as it makes Mo 3+ formation less facile. This theory provides a cohesive explanation for the origin of activity in Mo-based HER catalysts, emphasizing the specific role of Mo atoms in forming hydrides and carrying out the HER from Mo 3+ , with implications for future Mo catalyst design.

Uncovering the photoelectronic/catalytic property modulation and applications of 2D MoS2: from the perspective of constructing heterogeneous interfaces

“…Bau found that the activity of Mo-based catalysts depends on the degree of reduction from Mo 4+ to Mo 3+ . 165 These results all provided guidance for the design and synthesis of HS catalysts at the atomic level.…”

Isolated Electron Trap‐Induced Charge Accumulation for Efficient Photocatalytic Hydrogen Production

“…Thus, it should be reasonable to conclude that the newly generated signal should be ascribed to unpaired electrons from the Mo species of CZS, demonstrating that the decorated Mo species can trap unpaired electrons from the CZS. This tentative conclusion has been reconfirmed by increasing the Mo loading contents, in which the intensity of the signal has been further enhanced, and more radical pairs have been detected [32, 33] …”

“…This tentative conclusion has been reconfirmed by increasing the Mo loading contents, in which the intensity of the signal has been further enhanced, and more radical pairs have been detected. [32,33] Photocatalytic H 2 evolution efficiencies have been assessed in a closed circulation system under visible light (λ > 420 nm) irradiation. Lactic acid (20 vol %) has been applied as the sacrificial agent to consume the generated hole in the photoexcitation process.…”

Oxidized Copper and Molybdenum Species Exclusively Boosting Electrocatalytic Hydrogen Evolution in Non-Extreme pH Carbonate Buffer Electrolyte

“…On the other hand, we have reported that, on electrochemically prepared NiMoO x , a Mo oxo species (most likely Mo 3+ that forms during the HER) supported on metallic Ni or NiMo alloy was responsible for the high HER activity as the site for hydride formation . This catalytic role of the Mo oxo species was also reported on other Mo-based electrocatalysts. , Because these mechanistic studies suggested the crucial role of partner atoms in activating the Mo oxo species, , it is worthwhile to design catalysts with Mo and other optimum elements for highly efficient HER.…”