Selective Synthesis of Bismuth or Bismuth Selenide Nanosheets from a Metal Organic Precursor: Investigation of their Catalytic Performance for Water Splitting.

Shumaila Razzaque,Neerish Revaprasadu,Ram K Gupta,Muhammad Aamir,Malik Dilshad Khan,Sanket Bhoyate,Javeed Akhtar,Muhammad Sher,Manzar Sohail

doi:10.1021/acs.inorgchem.0c02668

Abstract

The development of cost-effective, functional materials that can be efficiently used for sustainable energy generation is highly desirable. Herein, a new molecular precursor of bismuth (tris(selenobenzoato)bismuth(III), [Bi(SeOCPh)3]), has been used to prepare selectively Bi or Bi2Se3 nanosheets via a colloidal route by the judicious control of the reaction parameters. The Bi formation mechanism was investigated, and it was observed that the trioctylphosphine (TOP) plays a crucial role in the formation of Bi. Employing the vapor deposition method resulted in the formation of exclusively Bi2Se3 films at different temperatures. The synthesized nanomaterials and films were characterized by p-XRD, TEM, Raman, SEM, EDX, AFM, XPS, and UV–vis spectroscopy. A minimum sheet thickness of 3.6 nm (i.e., a thickness of 8–9 layers) was observed for bismuth, whereas a thickness of 4 nm (i.e., a thickness of 4 layers) was observed for Bi2Se3 nanosheets. XPS showed surface oxidation of both materials and indicated an uncapped surface of Bi, whereas Bi2Se3 had a capping layer of oleylamine, resulting in reduced surface oxidation. The potential of Bi and Bi2Se3 nanosheets was tested for overall water-splitting application. The OER and HER catalytic performances of Bi2Se3 indicate overpotentials of 385 mV at 10 mA cm–2 and 220 mV, with Tafel slopes of 122 and 178 mV dec–1, respectively. In comparison, Bi showed a much lower OER activity (506 mV at 10 mA cm–2) but a slightly better HER (214 mV at 10 mA cm–2) performance. Similarly, Bi2Se3 nanosheets were observed to exhibit cathodic photocurrent in photoelectrocatalytic activity, which indicated their p-type behavior.

Highlights

Layered materials, when thinned down to their atomic limits, are referred to as two-dimensional (2D) materials that exhibit unique properties as compared to their bulk counterparts
The chalcogenide atoms (i.e., Se or Te), probably due to their flow rate was adjusted to 180 sccm, and the deposition of Bi2Se3 films instability and the handling difficulties associated with them
The synthesized molecular precursor was used for the preparation of Bi or Bi2Se3 nanosheets by the colloidal method

Summary

■ INTRODUCTION

Layered materials, when thinned down to their atomic limits, are referred to as two-dimensional (2D) materials that exhibit unique properties as compared to their bulk counterparts. The sample was analyzed by EDX analysis to observe the presence of selenium, which might indicate the formation of Bi2Se3 as an impurity phase; the EDX analysis shows the presence of only bismuth (Figure 3b). For Ni foam to obtain a current density of 10 mA cm−2, an overpotential of 440 mV is required, which clearly indicates that the catalytic activity is coming from Bi2Se3 nanosheets. The durability of the bismuth electrode as an HER catalyst was studied using cyclic voltammetry (Figure 9c) and chronoamperometry (Figure 9d) As seen from both studies, the Bi2Se3 electrode indicated a stable performance up to 1000 cycles of study, and after an initial decrease in the current density, which may be probably due to the surface oxidation of bismuth, a steady state was indicated for over 18 h of chronoamperometric study. The Bi2Se3/FTO photocathode acted as an efficient water reduction catalyst in the neutral sodium sulfate solution and could be a promising candidate for cathodic water-splitting applications

■ CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES