The Pt-interfacial-reaction-based quantitative detection of trace H2 released from palladium hydride in aqueous solutions

Abstract

Hydrogen gas holds tremendous potential across various domains, encompassing industrial applications, medical usage, and scientific research, among others. The precise and reliable detection of hydrogen gas is of paramount importance to ensure its safe utilization and accurate control of associated reactions, among other considerations. However, conventional approaches for quantitatively detecting H2, such as gas chromatography and hydrogen sensors, primarily focus on gas-phase detection, neglecting the detection of trace amounts of H2 in the liquid phase. This limitation becomes particularly pertinent when employing palladium hydride (PdHx) as a slow-releasing agent of hydrogen for medical purposes, necessitating the quantification of H2 released from PdHx in aqueous solutions, which is not straightforward to accomplish. This study presents a straightforward and convenient electrochemical method for quantifying H2 in an aqueous solution released from PdHx. The proposed method establishes a linear relationship between the theoretical concentration of H2 in the solution and the amount of H2 that reacted on the working electrode. Consequently, by measuring the amount of H2 that reacted on the working electrode in a PdHx dispersion, the actual concentration of H2 can be determined using the established linear relation. Specifically, it was found that the concentration of H2 released by 200 μg/mL PdHx at room temperature was determined to be 0.23 mM. To validate the findings, a simulation of the hydrogen detection reaction was conducted, which exhibited good agreement with the experimental results. The simulation results suggest that the presence of a peak near the primary hydrogen oxidation peak could be attributed to the adsorption of H2 and H+ near the electrode surface, and this effect diminishes with increasing temperature due to the weakening of species adsorption at elevated temperatures. Moreover, this study also demonstrated the quantitative verification of O2 in an aqueous solution using a similar method. The detection of trace amounts of H2 or O2 in aqueous solutions can find applications in determining the actual production of H2 in hydrogen evolution reactions facilitated by molecular catalysts and evaluating the trace amounts of H2 in photocatalysis as a complementary technique to gas chromatography. This methodology holds significant potential for advancing various areas of research.