Pd₇Se₂ nanospheres as an electrocatalyst for the hydrogen evolution reaction (HER)

Palladium selenide exists in several binary phases including Pd₁₇Se₁₅, PdSe₂, Pd₇Se₄, Pd₃Se, Pd_4.5Se, Pd₇Se₂, Pd₈Se and Pd₄Se. Among them, Pd₇Se₂ is attractive because it is palladium-rich in terms of the composition. During the catalysis, the availability of a high content of palladium in the material may be beneficial and may offer a high number of catalytically active sites. It may lead to achievement of a better performance than the other phases of palladium selenides. Very few studies have been conducted on the synthesis and applications of Pd₇Se₂. In the present study, for the first time, electrocatalytically active palladium-rich nanospheres of Pd₇Se₂ have been found to show potential to perform the HER. The development of this nanomaterial has been carried out using PdCl₂(Ph₂Se)₂ as a single molecular precursor. Complex 1 is reported as the first and an easily synthesizable single molecular precursor for the development of Pd₇Se₂. HR-TEM, FE-SEM, SEM-EDS, P-XRD, XPS and TGA studies have been conducted to characterize the Pd₇Se₂ NPs. The nanospheres perform very well as the electrocatalyst. While carrying out the hydrogen evolution reaction (HER), they require an overpotential of only 162 mV to drive a current density of 10 mA cm^-2, and an extremely low Tafel slope value of 37 mV dec^-1 is achieved. The electrocatalyst is stable and does not undergo degradation even after 30 hours of the HER process.