Physical Barricading at the Nanoscale: Protecting Pyrite from Weathering toward Efficient and Stable Electrocatalysis of the Oxygen Evolution Reaction

Abstract

The unique atomic arrangement and excellent charge transfer properties of two-dimensional (2D) metal chalcogenides (MX 2 ; M = transition metal, X = S, Se) make them effective electrocatalysts toward water splitting. But, so far, none of them have been able to replace noble-metal catalysts for the oxygen evolution reaction (OER), and it remains a great challenge to develop these catalysts. Specifically, cost-effective and earth-abundant FeS 2 has shown potential, but it is less acknowledged due to the associated weathering process. Here, we report a spin-coated TiO 2 layer on hydrothermally synthesized 2D-FeS 2 nanoplates to control weathering through physical barricading at the nanoscale. Notably, the electrochemical and chemical weathering studies suggest that the TiO 2 layer stabilized FeS 2 oxidation in alkaline solution, while the latter gets oxidized without TiO 2 overlayers. To the best of our knowledge, this would be the first report on an FeS 2 /TiO 2 photoanode for efficient and stable OER without any composite or doping. It displayed improved long-term durability of OER activity. Moreover, the annealed crystalline leaky TiO 2 layer (∼72 nm) remarkably displayed enhanced charge transfer at the FeS 2 /TiO 2 interface. Also, Mott−Schottky measurements confirmed that the leaky TiO 2 served as a protective layer (physical barrier) against the weathering of FeS 2 . The current study may provide new insights into the rational design of low-cost FeS 2 /TiO 2 layered electrocatalysts for OER and renewable energy applications.

Coordination compound-derived La-doped FeS2/N-doped carbon (NC) as an efficient electrocatalyst for the oxygen evolution reaction

“…2b, the peaks at 332 and 372 cm −1 in the Raman spectra of FeS 2 /NC and La-doped FeS 2 /NC-0.33 are ascribed to Fe–S. 18 The peaks at ∼1314 and 1527 cm −1 are the D and G peaks of carbon, 19 and the peaks at 903 and 1048 cm −1 are attributed to the amorphous carbon. 20 The results prove the presence of FeS 2 and carbon in the samples.…”

Enhanced oxygen evolution performance by the partial phase transformation of cobalt/nickel carbonate hydroxide nanosheet arrays in an Fe-containing alkaline electrolyte

“…Furthermore, Mott–Schottky measurements were applied to analyze the electronic conductivity. According to the previous reports, 67,68 electrochemical Mott–Schottky measurements can be performed to check the correlation between the flat band potential and charge carrier density at electrode/electrolyte interfaces as below:where C is the capacitance (F cm −2 ), ε 0 is the permittivity of the vacuum (8.854 × 10 −12 F cm −1 ), ε r is the dielectric constant of the electrocatalyst, N D is the donor density (cm −3 ), E is the applied potential, E FB is the flat band potential, k B is the Boltzmann constant, T is the thermodynamic temperature, and e is the electronic charge (1.602 × 10 −19 C). Here, N D is inversely proportional to the slope of the Mott–Schottky curve.…”

“…Furthermore, Mott-Schottky measurements were applied to analyze the electronic conductivity. According to the previous reports, 67,68 electrochemical Mott-Schottky measurements can be performed to check the correlation between the flat band potential and charge carrier density at electrode/electrolyte interfaces as below:…”

Recent Progress in Transition-Metal Sulfide Catalyst Regulation for Improved Oxygen Evolution Reaction

“…Theoretically, the catalyst materials with much higher surface area and electronic conductivity are more suitable for electrocatalysis reactions. Although the 2D nanomaterials have high surface areas, their surfaces are not completely available, because of the easy structure restack; moreover, the conductivity of some 2D nanomaterials like FeS 2 83 is not satisfactory. Therefore, it is necessary to maintain the high surface area exposure for the fabrication of novel 2Dbased nanomaterials.…”