Modification Of Pd Nanoparticles For An Enhanced Electrocatalytic Hydrodechlorination Reaction

In recent years,with the rapid development of economy,water pollution has become increasingly serious.Chlorophenol(CP)represent one typical class of persistent organic pollutants in water bodies,and are acute toxic,bioaccumulative,carcinogenic and strongly resistant to natural degradation.To alleviate their threat to ecological safety,it is highly desirable to develop technologies those can detoxify CP in an effective and environmentally-friendly way.Compared to various treatments of chlorinated organic pollutants,electrocatalytic hydrodechlorination(EHDC)stands out and has excellent application prospects for its high efficiency,no secondary pollution and mild conditions.Due to the superior properties and high catalytic activity in EHDC,the precious metal palladium(Pd)has become a favorable research subject.However,it has been hindered to some certain extent in practical applications of environmental restoration because of its high price.Therefore,it has become a critical issue on how to improve the effective utilization rate of Pd-based nanomaterials in EHDC.It is well known that the performance of a transition-metal catalyst is often boosted via the addition of a promoter or by alloying with another element.The promoter(or the second element of an alloy)can slightly change the energy of reaction intermediates on catalyst surface via shifting the d-band center or electrostatic interactions and normally accounts for a minor part of the catalytic system.Studies of the EHDC reaction using monodisperse AgPd nanoparticle(NP)model catalysts were conducted.The results reveal the essential role of the catalytically inert Ag component in promoting bimetallic AgPd nanocatalyst’s activity for the conversion of 2,4-dichlorophenol(2,4-DCP)to phenol(P).The EHDC reaction rate,current efficiency,and product selectivity were systematically investigated,leading to the observation of a volcano-type activity dependence on the Ag content in bimetallic NPs.The combination of kinetics analyses and density functional theory(DFT)calculations demonstrates that the balance of 2,4-DCP adsorption and P desorption is the dominant factor for EHDC efficiency rather than other processes(e.g.,hydrogen adsorbent formation).The presence of Ag,if precisely controlled in the proper range,alleviates the overstrong adsorption of P,allowing for a much enhanced EHDC kinetics compared to single-component Pd.This discovery provides a deep understanding of the EHDC mechanism over bimetallic nanocatalysts and a facile approach to optimizing this important environmental electrocatalysis strategy.Previous studies have shown that non-metallic elements(e.g.Boron,Phosphorus)doping into the Pd NPs can also boost their electrocatalytic performances.The boosting effect was usually attributed to the shrink of the Pd crystal lattice after introduction of the B atom,leading to the modification of the spatial electronic structure of Pd.Here,the B-doped Pd nanoparticle catalysts supported on carbon(C)were then synthesized by a surfactantfree wet-chemical reduction approach.The combination of material characterization,density functional theory(DFT)calculations and electrochemical test reveals that B doping changes the electronic structure of Pd and the adsorption strength to 2,4-DCP and P,which is beneficial to the EHDC reaction.This result further validates the EHDC reaction mechanism of Pd-based nanomaterials and improves the EHDC economic-viability of Pd-based catalysts in the field of environmental remediation.This work provided deep insight into the EHDC mechanism over the bimetallic NPs,and also developed efficient strategies to improve the EHDC performance of Pd-based catalysts,which should be of significance to the applications of EHDC technology for practical enviromental remediation.