X-ray diffraction study on the effects of hydrogen on Pd60Cu40 wt% foil membranes

Hydrogen solubility and diffusivity at Σ3 grain boundary of PdCu

First principles calculations have been performed to comparatively reveal hydrogen solubility and diffusivity at grain boundaries of BCC and FCC PdCu phases. It is found that the temperature-dependent hydrogen solubility at BCC Σ3 (112) GB of PdCu seems much higher than that in BCC PdCu bulk, while hydrogen solubility in FCC Σ3 (111) GB of PdCu is much lower than that in its corresponding FCC bulk. Calculations also reveal that grain boundary has an important effect on hydrogen diffusion of BCC and FCC PdCu, i.e., hydrogen diffusivities of BCC Σ3 (112) and FCC Σ3 (111) grain boundaries of PdCu seem much smaller and bigger than those of its corresponding bulks, respectively. The predicted results could deepen the comprehension of hydrogen solubility and diffusion of PdCu phases.

Palladium/cobalt nanowires with improved hydrogen sensing stability at ultra-low temperatures

The metallic dopants in palladium (Pd) sensing materials enable modification of the d-band center of Pd, which is expected to tune the α-β phase transitions of the PdH_x intermediate, thus improve the sensing stability to hydrogen. Here, the boosted hydrogen-sensing stability at ultra-low temperatures has been achieved with palladium/cobalt nanowires (PdCo NWs) as the sensing material. The various Co contents in PdCo NWs were modulated via AAO-template-confined electrodeposition. The temperature-dependent sensing evaluations were performed in 0.1-3 v/v% hydrogen. Such sensors integrated with PdCo NWs are able to stably detect hydrogen as low as 0.1 v/v%, even when the temperature is lowered to 273 K. In addition, the critical temperatures of "reverse sensing behavior" of the PdCo NWs (Pd₈₂Co₁₈: T_c = 194 K; Pd₆₃Co₃₇: T_c = 180 K; Pd₃₃Co₆₇: T_c = 184 K) are observed much lower than that of pristine Pd NWs (T_c = 287 K). Specifically, the Pd₆₃Co₃₇ NWs (∼37 at% Co content) sensor shows outstanding stability of sensing hydrogen against α-β phase transitions within the wide temperature range of 180-388 K, which is attributed to both the electronic interactions between Pd and Co and the lattice compression strain caused by Co dopants. Moreover, the "reverse sensing behavior" of the PdCo NWs is explicitly interpreted using the α-β phase transition model.