Unveiling active sites by structural tailoring of two‐dimensional niobium disulfide for improved electrocatalytic hydrogen evolution reaction

Abstract

Here we report, unveiling the active sites for improved electrocatalytic hydrogen evolution reaction (HER) by structural tailoring of Niobium Disulfide (NbS 2). NbS 2 synthesized by chemical vapor deposition method, structural deformation is carried out by post-argon plasma and annealing treatment. Plasma-treated (P.T) NbS 2 exhibits layer-by-layer stacked (≈250 nm) long and (≈200 nm) wide flakes, which show more edge sites and demonstrates low hydrogen evolution activity. Annealed NbS 2 flakes are enlarged in size (≈1 μm) having more surface area which shows additional active basal plane sites and demonstrate remarkable HER performance at 10 mA cm −2. As the thickness of NbS 2 is reduced, more basal planes are exposed hence improved HER activity was achieved. This enhanced electrocatalytic change demonstrates that the basal planes are the main active sites for HER in NbS.

Acid‐durable, high‐performance cobalt phosphide catalysts for hydrogen evolution in proton exchange membrane water electrolysis

“…The overpotentials at 10 mA/cm 2 increase in the order of Co-P-0.3 (143.85 mV) < Co-P-0.2 (167.11 mV) < Co-P-0.4 (171.59 mV) < Co-P-0.1 (227.38 mV) < Co-P-0.5 (280.89 mV) < Co-P-0.6 (345.98 mV) < Co (346.27 mV), exhibiting a volcano-like trend and showing the best HER performance for Co-P-0.3, that is, Co 94 P 6 . When compared with commercial Pt-based catalysts and others, the lowest overpotential of 143.85 mV in the case of Co-P-0.3 was still higher than those of Pt/C on Ti (14 mV), 32 Pt/C on CP (10 mV), 77 NiS 2 -Ni(OH) 2 (90 mV), 78 and MoS x /Ni-metalorganic framework-74 (114 mV) 79 but comparable to other non-PGM catalysts such as CoP (130 mV), 80 FeMoS (140 mV), 81 and N, P-dual-doped MoS 2 (147 mV) 82 and even better than [Mo 3 S 13 ] 2À (188 mV), 50 MoS 2 (190 mV), 83 NbS 2 (207 mV), 84 CoCu (342 mV), 27 and VS 2 (350 mV). 85 In addition, the Tafel slopes of each catalyst at the fourth cycle (Figure 5H) exhibit the same volcano-like trend, showing the lowest slope of 60.10 mV/dec for Co-P-0.3 (Co 94 P 6 ), which is comparable to results obtained previously for Co-P, that is, Tafel slopes from 45 to 82 mV/dec.…”

Plasma Processing and Treatment of 2D Transition Metal Dichalcogenides: Tuning Properties and Defect Engineering

“…Plasma treatment creates a higher density of defects and edges in 2D TMDs, leading to enhanced catalytic activity. However, care must be taken because excess amounts of defects may decrease the active sites due to etching and/or overdoping. ,,,,,, For instance, the optimum values for concentration of chalcogen vacancies produced by Ar plasma for best catalytic activity of 1T-MoTe 2 and 2H-MoTe 2 are found to be 3.18 × 10 14 cm –2 and 1.02 × 10 14 cm –2 , respectively . Theoretical studies have shown the sulfur vacancies to reduce the free energy for hydrogen adsorption (Δ G H ) by introducing new localized bands near the Fermi level (Figure a,b) .…”

A review of the porous transport layer in polymer electrolyte membrane water electrolysis

“…In contrast, electrolysis techniques (water electrolysis via renewable energies, thermal water splitting with Cu-Cl and S-I cycles, high-temperature electrolysis) yield up to 99.999% pure hydrogen and prove to be environmentally friendly candidates. 8 While high production cost is their main drawback. For water electrolysis to dominate hydrogen production, it is required to operate at high efficiency and low cost.…”

“…The traditional techniques (natural gas steam reforming, coal gasification, biomass gasification) qualify for the advantages of low cost and ease of scale‐up; however, they are disadvantageous from an environmental perspective. In contrast, electrolysis techniques (water electrolysis via renewable energies, thermal water splitting with Cu‐Cl and S‐I cycles, high‐temperature electrolysis) yield up to 99.999% pure hydrogen and prove to be environmentally friendly candidates 8 . While high production cost is their main drawback.…”