Wet-Chemical Preparation and Oxygen Reduction Properties of Nickel-Based Sulfide Electrocatalysts for Polymer Electrolyte Fuel Cell

Iwaya, Wataru; Takase, Satoko

doi:10.5796/electrochemistry.79.364

Cited by 6 publications

(1 citation statement)

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“…The effective charge transportation from cocatalyst to photocatalyst is also observed in NiS loaded CdS sample 194. In addition, as a cocatalyst, NiS 2 should be able to serve as reactive sites for H 2 evolution, as presented in cathodic H 2 evolution reactions during electrolysis 246,247. Xu et al reported that NiS on the surface of CdS would…”

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confidence: 86%

Deposition of economic cocatalysts on graphitic carbon nitride for efficient photocatalytic hydrogen generation

Yin¹

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Energy crisis and environmental issues are two most severe problems faced by all human beings on this planet. In order to solve the two problems, researchers are seeking for alternative energies other than fossil fuels. The alternative energies should be abundant, clean as well as sustainable. From this point of view, hydrogen is a good candidate. Hydrogen could be generated from a clean process, photocatalytic water splitting, in which semiconductor photocatalyst is a key factor. Polymeric graphitic carbon nitride (g-C 3 N 4), which could respond to visible light with a proper band gap of 2.7 eV and suitable conduction band (CB) of-1.1 eV to reduce protons, is demonstrated to be able to achieve photocatalytic H 2 generation. However, pristine g-C 3 N 4 exhibits a poor performance for photocatalytic H 2 generation due to the fast recombination of photoexcited electrons and holes. Whereas loading of noble metal cocatalysts such as Pt could enhance the performance. This project aims at suppressing the charge carrier recombination and thus enhancing the photocatalytic activity of g-C 3 N 4 by depositing earth abundant and low-cost cocatalysts, e.g. bimetallic alloy, PtCo, and noble metal free NiS 2. Firstly, the noble metal Pt cocatalyst was partially replaced with Co and a series of PtCo alloys with different compositions were loaded on to the surface of g-C 3 N 4 via the solvothermal method. Different amounts of Pt and Co precursors were added to adjust the compositions and the H 2 evolution results indicated the highest activity was obtained at an atomic ratio of 2.5 to 1(Pt to Co). This Pt 2.5 Co/ g-C 3 N 4 with 1wt% cocatalyst loading exhibited an even higher activity than that of Pt (1 wt%) loaded g-C 3 N 4 prepared under same conditions. The constant H 2 evolution IV rate of 1wt% Pt 2.5 Co/ g-C 3 N 4 under continuous 25-hour illumination under visible light suggested this alloy is highly stable on g-C 3 N 4. The photoluminescence spectra and photoelectrochemical properties measurements imply that PtCo alloy could efficiently inhibit the recombination of photogenerated electrons and holes and therefore enhance the photocatalytic H 2 production activity of g-C 3 N 4. Secondly, the noble metal Pt cocatalyst was fully replaced with earth abundant and noble metal free cocatalyst, NiS 2. NiS 2 /g-C 3 N 4 composite with different weight percentages were synthesized via the hydrothermal method using thiourea and nickel acetate tetrahydrate as precursors. The presence of NiS 2 was confirmed by X-ray diffraction pattern (XRD), transmission electron microscope (TEM) and Xray photoelectron spectra (XPS). The H 2 evolution test indicates that NiS 2 loading could increase activity of g-C 3 N 4 dramatically and 2 wt% loading of NiS 2 on g-C 3 N 4 shows the best performance, even better than 1 wt% Pt/g-C 3 N 4 from photodeposition. Photoluminescence (PL) spectra of the samples suggest that the enhancement is associated with the more effective charge carrier separation as well. In summary, this thesis is devoted to developing...

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confidence: 86%