Preparation And Multiple Effect Electric Catalytic Performance Research Of NiCu@PdRu(PdIr)/C Nano Electrocatalysts

In Alkali-dissolution and carbonizion-precipitation process is an efficient way to improve the production efficiency of alumina. The key of the technique is to realize the recycle by the electrolysis of sodium carbonate. But the single cell voltage of traditional electrolysis consumes more than 2.5 V. We propose to replace the traditional oxygen evolution anode with hydrogen anode, matching the commercial hydrogen evolution cathode to build energy saving hydrogen anode-hydrogen evolution cathode electrolytic model and reduce the cost, the key of the propose is the development of low cost, low over-potential and high poison tolerance hydrogen anode.Pd and Pt are two of the few metals with high catalytic activity in hydrogen oxidation reaction (HOR). Pt metal has the highest catalytic activity for hydrogen oxidation reaction. But the application of commercial Pt/C in industry is limited due to the lack of reserves and high price. By contrast, Pd has relative low price, and the geological reserves is far higher than that of Pt. So we choose the metal Pd, who has the similar properties as the main element in catalyst. We use noble metal Ni, Cu and their alloy as the "core". Reduce the Pd on the outer of core to synthesis core-shell catalyst. To further reduce the dosage of Pd and regulate the activity of catalysts, stability, and poison tolerance. In addition, we doped few Ru, Ir to improve the hydrogen oxidation activity and methanol-tolerance ability.This paper study four metals core-shell structured NiCu@PdM/C (M=Ru or Ir) catalyst, which use the alloy of Ni and Cu as core, the Pd-Ru or Pd-Ir as shell. Catalyst was synthesized in two steps, first prepared the NiCu/C precursor in H2 at high temperature, then deposed the certain mass ratio of Pd and other transition metal through EG reduction method assistant with replacement onto NiCu/C selectively. The NiCu@PdM/C catalyst was constructed through a series of regulation and control. This paper investigates the noble metal load method (displacement method, hydrothermal method, toluene reflux method and ethylene glycol reflux method), the preparation conditions, the doping metal and the proportion of doped materials in the catalysts. The morphology, composition and kinetics of the catalyst were studied by physical characterization and electrochemical tests, to determine the optimal performance of core-shell structure nanometer catalyst. The HRTEM result indicated that four metal nanoparticles load on the carbon supported homogeneous with a quiet small average size 1.84nm. TG and ICP results indicate Ni, Cu dissolution selectively when the reducing the noble metal. This is advantageous to the alloying of Pd, Ru and Ni, Cu, also advantagous to the regulation of precious metal lattice spacing and load condition. It shows a higher electrochemical activity area even if the metal load is reduced by 50%. There is only a 14mV gap between NiCu@Pd9Rul/C, which perform the highest activity, and equal noble metal loading commercial Pt/C. Apply the catalyst in electrolysis experiment, it reduce the cell voltage by 1.18V effectively, and keep a stable ability after a long time electrolysis.NiCu@PdIr/C catalyst synthesized by the same method also has small particle sizes. The average diameter of metal particles is only 2.06nm. Synergy between Pd shell and Cu core lead to electron binding energy of Pd decreased, performing in XPS characterization, indicated that d orbital cavity increased. There is only a less than 8mV gap between NiCu@Pd4Irl/C, which perform the highest activity, and equal noble metal loading commercial Pt/C in hydrogen oxidation test. The HOR performance has improved compare to NiCu@Pd9Rul/C. Besides, the catalyst exhibits high methanol-tolerance ability. It has a direct link with the easy formed Ir-OH on the surface of Ir, which can remove the oxidation of intermediate product.Benefit from special components, structural features and the synergistic effect of Pd-Ir, the NiCu@PdIr/C exhibits a high catalytic activity in the HER^ OER and HOR tests. The OER Current density of NiCu@PdIr/C is 8 times the commercial Pt/C,2 times the commercial PtRu/C at the same potential. The over potential is consistent with the Pt/C catalyst when the current density of HER is 10mA/cm2. The half wave potential of ORR polarization curve perform 12mV ahead of time, compared with equal noble metal loading Pt/C. The NiCu@PdIr/C also has high methanol tolerance as the ORR catalyst. These data show that the NiCu@PdIr/C is an excellent four functions catalyst with HOR, ORR, HER and OER ability.