Abstract
The work presents a research on preparation and physical and electrochemical characterisation of dc magnetron sputtered Pd films envisaged for application as hydrogen storage in a chip-integrated hydrogen microenergy system. The influence of the changes in the sputtering pressure on the surface structure, morphology, and roughness was analysed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AMF). The electrochemical activity towards hydrogen adsorption/desorption and formation of PdH were investigated in 0.5 M H2SO4 using the methods of cyclic voltammetry and galvanostatic polarisation. The changes in the electrical properties of the films as a function of the sputtering pressure and the level of hydrogenation were evaluated before and immediately after the electrochemical charging tests, using a four-probe technique. The research resulted in establishment of optimal sputter regime, ensuring fully reproducible Pd layers with highly developed surface, moderate porosity, and mechanical stability. Selected samples were integrated as hydrogen storage in a newly developed unitized microenergy system and tested in charging (water electrolysis) and discharging (fuel cell) operative mode at ambient conditions demonstrating a stable recycling performance.
Highlights
Nowadays the usage of hydrogen as a new environmentally clean energy carrier is already a reality
In the last years the boom in the portable electronic devices has led to an increased importance of the microfuel cells as an alternative power supply for consumer electronics such as multimedia, laptops, mobile phones, and so forth, as well as for powering of emergency and military equipment, different sensors, and medical devices
Most of the hydrogen μFCs reported in the literature work in a passive mode and consist of several membrane electrode assemblies (MEA) connected in a stack and a hydrogen reservoir [1, 2]
Summary
Nowadays the usage of hydrogen as a new environmentally clean energy carrier is already a reality. The same authors later on have coupled the μFC to an electrolyser cell, creating a fuel cell accumulator that acquires the ability to recharge the hydrogen storage on board. This rechargeable μFC reached a power output about 300 μW⋅cm−2, while the achieved discharge capacity was just 2.7% of the palladium theoretical hydrogen storage capacity. The hydrogen storage material is an integrated part of the system It is charged via water electrolysis and used to feed the system during its reverse operation in a fuel cell mode. The material of choice is Pd, which is well known for its high hydrogen solubility and diffusivity, in a thin film form, along with its excellent corrosion resistance
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