Rational Design of Single Molybdenum Atoms Anchored on N‐Doped Carbon for Effective Hydrogen Evolution Reaction

Abstract

The highly efficient electrochemical hydrogen evolution reaction (HER) provides a promising pathway to resolve energy and environment problems. An electrocatalyst was designed with single Mo atoms (Mo-SAs) supported on N-doped carbon having outstanding HER performance. The structure of the catalyst was probed by aberration-corrected scanning transmission electron microscopy (AC-STEM) and X-ray absorption fine structure (XAFS) spectroscopy, indicating the formation of Mo-SAs anchored with one nitrogen atom and two carbon atoms (Mo N C ). Importantly, the Mo N C catalyst displayed much more excellent activity compared with Mo C and MoN, and better stability than commercial Pt/C. Density functional theory (DFT) calculation revealed that the unique structure of Mo N C moiety played a crucial effect to improve the HER performance. This work opens up new opportunities for the preparation and application of highly active and stable Mo-based HER catalysts.

Heterostructures Composed of N‐Doped Carbon Nanotubes Encapsulating Cobalt and β‐Mo2C Nanoparticles as Bifunctional Electrodes for Water Splitting

“…Thep eaks around 780/795.7 eV can be ascribed to oxidized Co species. Ag radual increase in the peak percentage of pyridinic N( Co@N-CNTs < Mo 2 C@N-CNTs < Co/b-Mo 2 C@N-CNTs) implies that the simultaneous introduction of Co and b-Mo 2 Ccan increase the percentage of pyridinic N species.T he high concentration of pyridinic Nc an not only improve electrical conductivity and surface wettability, [31,32] but the pyridinic Nc an also accept electrons from adjacent Catoms,t hus facilitating the adsorption of water-oxidation intermediates (OH À ,O OH À )a sr ate-determining steps. [27,28] TheM o3 ds pectrum was deconvoluted into six singlets ascribed to Mo 2+ (228.4/231.6 eV), Mo 4+ (229.2/ 232.3 eV), and Mo 6+ (232.9/235.6 eV), corresponding to the main Mo 2 Cs pecies and slightly surface oxidized MoO x species (Figure 2b).…”

“…High durability is an important criterion for an efficient electrocatalyst. [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] To unveil the electronic interactions between b-Mo 2 C, Co, and N-CNTs,w es ystematically performed and compared DFT calculations on the adsorption free energy of H* (DG H* represents an adsorption site) of several models,i ncluding CNTs,N -CNTs,C o@N-CNTs,M o 2 C@N-CNTs,a nd Co/b-Mo 2 C@N-CNTs,d uring the HER (see Figure S12). Accelerated LSV was also conducted continuously for 1000 cycles,and the overpotential of Co/b-Mo 2 C@N-CNTs only increased by about 13 mV at j 10 (see Figure S11).…”

“…Furthermore,u pon encapsulating Mo 2 Cw ithin N-CNTs,t he DG H* value was effectively tuned, owing to the improved H*-chemisorption strength, which is promoted by the interfacial Mo-N coupling. [27][28][29][30][31][32][33][34][35][36][37] To better understand the higher OER activity of the Co/b-Mo 2 C@N-CNTs,w ei nvestigated the detailed OER mechanism using DFT calculations (Figure 4e,f). [23,36] Thee lectrocatalytic OER performance of the catalysts was also evaluated in 1.0 m KOH.…”

Atomically Dispersed Molybdenum Catalysts for Efficient Ambient Nitrogen Fixation

“…[20] Metal-free catalysts,s uch as boron carbide, [23] porous carbon, [24] and their derivatives, [25,26] are alternative materials,o fw hich boron carbide (B 4 C) nanosheets presented the highest FE of 15.95 %a nd ac orresponding NH 3 yield rate of 26.57 mgh À1 mg À1 cat . [28][29][30][31] Considering that nearly all natural N 2 is fixed with the enzyme nitrogenase produced in bacteria, and the active center of the nitrogenase is aM o-based structure, [32] single Mo atoms could be ap romising catalyst. Thea ctivity of metal-based nanocatalysts is highly influenced by their size.…”

“…Brunauer-Emmett-Teller (BET) analysis gives as pecific surface area of 302.3 m 2 g À1 and indicates the hierarchical existence of meso-and macroporous features ( Figure S2). [30] Moreover, elemental mapping performed by energy-dispersive X-ray spectroscopy (EDS) indicates the presence of homogeneous distributions of Mo,C ,a nd Nt hroughout the architecture (Figure 1c;F igure S3). [30] Moreover, elemental mapping performed by energy-dispersive X-ray spectroscopy (EDS) indicates the presence of homogeneous distributions of Mo,C ,a nd Nt hroughout the architecture (Figure 1c;F igure S3).…”