Controlled Synthesis Of Nobel Metal On Cuprous Sulfide Composites And Its Electrocatalytic Performance

Electrochemical synthesis is a green and safe technology for chemical synthesis.Catalysts are the key materials needed in electrochemical synthesis,which typically determine the activity,selectivity,and durability of the overall reaction.Precious metal nanocatalysts are widely used in practical electrochemical devices because of their excellent electrocatalytic properties.Typically,the precious metals nanoparticles（NPs）need to be loaded onto suitable carriers to inhibit the agglomeration of tiny particles at high surface energy.Meanwhile,the carrier-metal interaction can regulate the electronic structure of the active center,inhibit the toxic deactivation of the active center,and enhance the activity and stability of the catalyst.Herein,we used Cu₂S nanoparticles as the carriers to load noble metal NPs because of the strong interaction between noble metals and sulfur.The Cu₂S-supported noble metal catalysts are adopted to catalyze ethanol electrooxidation and two-electron oxygen reduction reactions.The enhanced electrocatalytic performance,including activity,selectivity,and stability,is demonstrated.The main findings are as follows:（1）Pd-Cu_2-xS catalysts were prepared by loading Pd onto the carrier Cu₂S,exhibiting enhanced catalytic activity and stability for ethanol electrooxidation.The Pd-Cu_2-xS catalysts were synthesized by the ion exchange method.The effects of reaction temperature,reaction time and Pd loading on the morphology and composition of the catalysts were investigated to further investigate their catalytic effects on the electro-oxidation of ethanol.Finally,the Pd-Cu_2-xS catalysts with the best mass activity were obtained.The catalyst was tested for stability at a potential of 0.6 V（vs.RHE）using the chrono-current method and exhibited better stability than Pd/C.The comparative experiments and characterization analysis showed that the performance improvement originated from the accelerated ethanol oxidation decisive step by the adsorption of hydroxyl groups on the carrier Cu_2-xS after oxidation.（2）Introduction of Au-based catalysts to further enhance the stability of Cu₂S-loaded catalysts for catalytic ethanol electro-oxidation reactions.The performance of the Au-Cu_2-xS electrocatalyst is significantly enhanced compared to Au/C,which is mainly attributed to the synergistic and electronic effects of the catalyst carrier.At the same time,due to the weak adsorption of the Au active site to the reaction intermediate,it cannot break the C-C bond,which avoids the"poisoning"phenomenon of the catalyst in the reaction,and the catalyst shows better stability.A liquid flow electrolytic cell was constructed with the synthesized Au-Cu_2-xS catalyst as the anode,and stable operation was achieved at a constant potential of 1.2 V for 20 h.The feasibility of using this catalyst as the anode material for electrolytic hydrogen production and electrochemical synthesis of high-value-added organic compounds using ethanol electrooxidation instead of anode OER reaction was verified in practice.（3）Using the high specific surface area provided by the nano-Cu₂S carriers and the anchoring effect of S to achieve uniform loading of high-loading Pt catalysts,an ion exchange method based on ethylene glycol solvent was developed to prepare Pt-Cu_2-xS composite electrocatalysts with different Pt dispersion states.The catalyst achieved high activity,selectivity,and stability for the preparation of hydrogen peroxide by two-electron oxygen reduction under acidic conditions with a half-wave potential of 0.95 V and more than 90%selectivity for H₂O₂in the potential range of 0.1～0.6 V.There was no significant degradation in performance after 5000 turns of continuous cyclic voltammetry scanning.Combined with the available reports,structural and comparative performance analyses indicate that the excellent catalytic performance and stability of the catalysts originate from the stable Pt-S bond between the carrier Cu₂S and Pt,while their two-electron oxygen reduction selectivity originates from the Pt active site alone.