All-pH Hydrogen Evolution by Heterophase Molybdenum Carbides Prepared via Mechanochemical Synthesis

Abstract

As non-precious-metal catalysts for the hydrogen evolution reaction (HER), molybdenum carbides have attracted extensive attention in recent years. Molybdenum carbides usually require high synthesis temperatures (>700 °C), which leads to a high cost. In this study, we report a controllable synthesis of heterophase molybdenum carbides (MoC/Mo2C) using a simple ball milling method without external thermal input. The as-obtained MoC/Mo2C catalysts exhibit excellent HER electrocatalytic activity and durability at all pH conditions in comparison with MoC or Mo2C alone. The interface of MoC/Mo2C formed in situ is the key factor in improving the electrocatalytic activity. This fabrication method is cheap and effective in generating heterophase interfaces, which can be employed in many other fields where interface engineering is needed.

Advanced and Durable Self-Standing MoC-Mo2C Electrode for Alkaline Hydrogen Evolution in Chlor-alkali Electrolysis

“…As revealed in Figure a, the full XPS spectrum confirmed that the sample consisted of Mo, C, and O . As depicted in Figure b, the Mo 3d XPS spectrum can be segmented into four states, namely, Mo 2+ (228.28, 231.60 eV), Mo 3+ (228.89, 232.63 eV), Mo 4+ (230.06, 234.69 eV), and Mo 6+ (233.06, 235.82 eV). − There is still controversy with the exact valence states of Mo in MoC and Mo 2 C. Typically, most scholars believe that Mo 2+ is dominant in Mo 2 C and the Mo 3+ is dominant in MoC. In addition, the higher valence states of Mo 4+ and Mo 6+ originate from MoO 2 and MoO 3 , which are caused by partial oxidation at the surface of MoC/Mo 2 C. ,, Figure c displays the C 1s XPS spectrum that can be fitted using four peaks, which are attributed to Mo–C (283.05 eV), C–C (284.80 eV), C–O (286.25 eV), and OC–O (288.48 eV) species. , In addition, evident peaks in the O 1s spectrum of O–H (530.53 eV), CO (531.84 eV), and Mo–O (533.01 eV) were derived from MoO 2 and MoO 3 due to the slight oxidation of the MoC–Mo 2 C surface (Figure d) .…”

Small-size composite Ni-Co/Mo2C/Co6Mo6C2@C prepared by a anchoring calcination strategy for efficient hydrogen evolution reaction in the acidic and alkaline conditions

“…In addition, there is a high specific surface area and hierarchical pore structure for Ni-Co/Mo 2 C/Co 6 Mo 6 C 2 @C, which can accelerate material transfer in the process of HER. Therefore, Ni-Co/Mo 2 C/Co 6 Mo 6 C 2 @C demonstrates great superiority for HER in acidic and alkaline conditions, which also excels that of some reported transition-based catalysts for HER (Table S1) [32][33][34][35][36][37][38][39][40][41][42] .…”

Recent Progress on Molybdenum Carbide-Based Catalysts for Hydrogen Evolution: A Review

“…As a half-reaction of water splitting, the hydrogen evolution reaction (HER) is a two-electron-proton coupling reaction that takes place on the surface of the cathode catalyst [27,28]. In acidic media, the hydrogen evolution reaction is generally considered to consist Nowadays, many methods have been proposed, such as optimization of synthesis methods [20], composites with carbon material [21], non-precious metal doping [22], transition metal doping [23], construction of heterogeneous structures [24], etc. Among them, the importance of sulphur-doping, Ni-doping, and heterophase structure on molybdenum carbide-based catalysts for enhancement of activity in acidic and basic media has been highlighted in this review.…”