Electrochemical Investigation of Si of Various Dopant Concentrations at Negative Overpotentials in Aqueous Electrolyte

Abstract

n-Type and p-type Si samples of various doping concentrations (1014–1019 cm–3) are investigated in hydrogen fluoride electrolyte using voltammetry and electrochemical impedance spectroscopy (EIS) at negative overpotentials. In addition to the features of solution resistance, space charge, and double layer common to all the doped-Si samples, up to six different types of low-frequency (lf) features are observed in the EIS spectra, depending on the dopant and its concentration. These lf features corresponding to the sequential or simultaneous hydride formation and evolution processes are well resolved on Si of appropriate dopant concentration, unlike in the case of the widely investigated Pt and Pd. The results reported here with Si, a semiconducting material, lend experimental credence to the proposed theoretical models of hydrogen evolution reaction (HER), and the spectra are similar to the simulated spectra reported in the literature.

Kinetics of Hydrogen Evolution Reactions in Acidic Media on Pt, Pd, and MoS2

“…Transition-metal dichalcogenides (TMDs) are the most investigated among the NPMCs. MoS 2 , generally used as a photocatalyst, shows reasonably good HER activity from an electrochemical perspective. − Recently, in this context, Priyadarshani et al analyzed HER on a semiconducting Si surface by electrochemical impedance spectroscopy …”

“…20−27 Recently, in this context, Priyadarshani et al analyzed HER on a semiconducting Si surface by electrochemical impedance spectroscopy. 28 In this study, temperature-dependent HER is investigated on three catalyst (Pt black, Pd black, and MoS 2 ) surfaces. The working electrode potentials at the respective temperatures are corrected using the definition of equilibrium potential.…”

Low-frequency inductive features in the electrochemical impedance spectra of mass-transport limited redox reactions

“…, MOR in Fig. 4, or in the case of the HER on Si 30 ) and are attributed to the faster surface relaxation. In the mass-transport limited region, the increase in lf EC parameter values with decreasing potential is quite unexpected because surface coverage continues to decrease, as is evident from the adsorption isotherm (Fig.…”

“…The decreasing values of EC parameters at higher negative overpotential confirm faster surface relaxation. 29,30…”

“…The decreasing values of EC parameters at higher negative overpotential confirm faster surface relaxation. 29,30 The circuit presented in Fig. 1 (hereafter denoted as Circuit 1) is widely used to model the one-adsorbate system, where R P is the polarization resistance across the electrode-electrolyte interface.…”