Black Phosphorus‐Based Compound with Few Layers for Photocatalytic Water Oxidation

Abstract

Although black phosphorus (BP) is an interesting 2D nanosheet material with a high hole mobility, its application in the photocatalytic water oxidation for O 2 evolution is not reported yet. Herein the use of BP coupled with a reductive hydroxide, Ni(OH) 2 , is reported for the first time. The developed photoassisted process confirms that the BP XPS measurements confirm that the oxidation state of BP is reduced through the photo-assisted loading method. The obtained PÀNi(OH) 2 samples present the steady and efficient photocatalytic water splitting for O 2 generation. Under the simulated sunlight irradiation in 0.1 M Na 2 S 2 O 4 solution, the O 2 generation rate can reach up to 15.7 mmol/(g catalyst *h) or 224.3 mmol/(g BP *h). The density functional theory (DFT) calculation suggests that the electrons and holes move to surface of BP and Ni(OH) 2 , respectively. The merit of self-polarization of PÀNi(OH) 2 ensures the stability of BP and achieves the photocatalytic O 2 generation from water.The importance of photocatalysis in the solar-to-chemical energy converison is widely confirmed and the structure of the studied materials (metal-semiconductor and semiconductorsemiconductor, etc.) plays a crucial role. [1-10] On the compound system, a heterojunction is always used to promote the photogenerated carriers separation and favor the migration across the interface. [7][8][9][10] Moreover, in order to reach a new equilibrium, the different work functions of the components induce the relocation of the Fermi levels. During these processes, the redistribution of the free carriers i. e. electrons and holes to different sides of the semiconductors leads to the formation of one intermediate region, which is named as the built-in electric field. [5][6][7][8][9][10] Under the illumination of incident light, the heterojunction will generate photogenerated electron-hole pairs, which are separated by the field and then move to the different sites to participate in reactions, thus the enhanced photocatalytic activity will be obtained. Furthermore, a few layered heterojunction structure will reduce the migration distance and then decrease the recombination, thus enhancing the final photocatalytic activity of the system.Black phosphorous (BP) is an interesting material with the high hole carrier mobility of ca. 105 cm 2 /V/s, [11][12][13][14][15][16][17][18][19][20] wide range of thickness-dependent direct bandgap of range of 0.3 to 2.0 eV and strong optical absorption near infrared region. Therefore, BP-based samples have been applied working as one photocatalyst [16][17] or co-catalysts, [18] in the photocatalytic field, especially in the application of water splitting, which has been thought as the promising strategy to solve the future or near global energy and environmental issues. [21][22] Owing to the more positive than the oxidation potential of O 2 /H 2 O and the reduction potential of H + /H 2 , BP can only be used for photocatalytic water reduction to H 2 generation. [16][17][18] The band edge positions of BP semiconduc...

Ultrathin Two‐Dimensional Semiconductors for Photocatalysis in Energy and Environment Applications

“…Based on the above‐mentioned advantages, 2D semiconductors nanosheets can establish a clear structure‐property relationship for studying the influence of the microstructure on the photocatalytic performance, which will undoubtedly play a significant role in promoting the photocatalytic activity . Although there are a lot of 2D reviews spring up in recent years, only a few progresses have made efforts to overview ultrathin 2D semiconductors applied in the significant field of photocatalysis.…”

Black Phosphorus-IGZO van der Waals Diode with Low-Resistivity Metal Contacts

“…In the Raman spectrum of p-BP, the peak A g 1 was observed at 361.7 cm –1 , showing the out-of-plane vibration mode, whereas the peaks B g 2 and A g 2 were observed at 438.4 and 466.4 cm –1 , respectively, showing the in-plane vibration modes, ,, as shown in Figure a. These modes of vibration indicate the high quality of the p-BP flakes without any oxidation. − The structural characterizations of the n-IGZO film after annealing at different temperatures were examined by XRD, as shown in Figure b. The scanning electron microscopy (SEM) images are presented in Figure S1 in the Supporting Information.…”

Recent Progress on Black Phosphorus‐Based Materials for Photocatalytic Water Splitting

“…They also developed a facile strategy for loading thin‐film BP on Ti foil surface to obtain advanced electrocatalytic oxygen evolution activity . In our recent work, the thin layered BP (80% monolayer) with a size smaller than 10 nm was used as a semiconductor, of which oxidation potential is more positive than H 2 O/O 2 . Layered Ni(OH) 2 owns a reduction property and presents the excellent water oxidation performance.…”