Influence of Mo (VI) on modified graphene in excellence of low cost composite activity over the noble metal for hydrogen evolution reaction in acidic media

Sustainable hydrogen production from water splitting is one of the most attractive methods for energy storage and conversion. Hydrogen evolution reaction is the production of hydrogen through the cathodic process in water electrolyzers. Pt exhibits excellent electrocatalytic activity in HER, but the scarcity and high prices of the noble metals prohibit their widespread applications [1]. The excellent electrocatalytic performance along with high abundance in earth and low-cost alternative to the precious metals has made Mo gradually become a rising star in clean energy fields. The several reports molybdenum (VI) complexes were used for H2 production [2]. In this perspective, for first time the complex of Mo (VI) supported functionalized graphene ([Mo-f-rGO]) has been investigated as a catalyst for H2 production. To provide the Mo ligands, GO was covalently modified with groups contained nitrogen and oxygen atoms. The performance of [Mo- f-rGO] catalysts can be improved by accompanying some noble metals. In contrast to Pt and Au, Pd is relatively cheaper than Pt and Au. In this paper were showed [Pd/Mo-f-G] catalysts to be significantly more active than either Pd or Mo alone for H2 production in acidic media. In Figure 1(a-b), FTIR spectra and SEM image of the (Pd/Mo-f-rGO) are illustrated. The synthesized samples with the various amounts of Pd and Mo complexes were evaluated as the HER electrocatalysts in 0.5 mol L-1 H2SO4 solution. Several electrochemical techniques such as cyclic voltammetry (CV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) were employed to determine the optimized composition for HER. Results showed that the addition of Mo complex to the Pd- functionalized graphene, makes the possibility of decrease the Pd amount in composite, with no activity drop. The composite with 5 wt% of Mo complex + 5 wt% of Pd, showed the onset overpotential (ηonset) of -83 mV, equal to the composite with 10 wt% of Pd. The obtained results and same activity of 5 wt% Mo complex + 5 wt% Pd compared to 10 wt% Pd guarantees the new synthesized structure application in acidic HER with the lowering of noble metal amount and decrease of electrocatalyst price.