Comprehensive study of adsorption kinetics for hydrogen sensing with an electroless-plated Pd–InP Schottky diode

In this work, a comprehensive adsorption model for hydrogen detection with an electroless-plated Pd–InP Schottky diode is proposed. The hydrogen adsorption reaction enthalpy (ΔH°) and entropy (ΔS°) are estimated as −44.1 kJ mol−1 and −125.5 J mol−1 K−1, respectively, based on the steady-state analysis. It is therefore unfavorable for hydrogen detection at high temperature. From kinetic analysis, the activation energy (Ea) for hydrogen adsorption is determined as 12.1 kJ mol−1, which is smaller than those obtained from Pd–GaAs and Pt–GaAs diodes. Based on these results, the hydrogen adsorption rate of Pd–semiconductor diode is strongly influenced by the nature of semiconductor substrate.