Engineering the epitaxial interface of Pt-CeO2 by surface redox reaction guided nucleation for low temperature CO oxidation

The interface between metal nanoparticles(NPs)and support plays a vital role in catalysis because both electron and atom exchanges occur across the metal-support interface.However,the rational design of interfacial structure facilitating the charge transfer between the neighboring parts remains a challenge.Herein,a guided nucleation strategy based on redox reaction between noble metal precursor and supportsurface is introduced to construct epitaxial interfaces between Pt NPs and CeO2 support.The Pt/CeO2 catalyst exhibits near room temperature catalytic activity for CO oxidation that is benefited from the well-defined interface structure facilitating charge transfer from CeO2 support to Pt NPs.Meanwhile,this general approach based on support-surface-induced-nucleation was successfully extended to synthesize Pd and Cu nanocatalysts on CeO2,demonstrating its universal and feasible characteristics.This work is an important step towards developing highly active supported metal catalysts by engineering their interfaces.

Carbon-CeO interface confinement enhances the chemical stability of Pt nanocatalyst for catalytic oxidation reactions

Noble metals are downsized to nano-/subnanoscale to improve their catalytic activity and atom-economy.However,the stabilities in chemical state and catalytic performance of these nanocatalysts often suffer during harsh conditions.For Pt nanoparticles(NPs)supported on CeO2,activated oxygen diffused from the support over-stabilizes the active sites of Pt,degrading its performance at mild temperature.In this work,Pt nanocatalysts with unique structure of triple-junction are synthesized by selectively growing Pt NPs on the carbon-CeO2 interface.Impressively,the Pt NPs exhibit much enhanced catalytic stability and high activity for CO oxidation at mild temperature.The enhancement is attributed to electron donation from graphitized carbon and the confinement effect from the high-density nanopores of the CeO2 support.The triple-junction of Pt-C-CeO2,combining the merits of CeO2 for activating O2 and electron donating capability of carbon,provides new inspiration to the fabrication of high-performance nanocatalysts.

Light-switchable catalytic activity of Cu for oxygen reduction reaction

The surface reactivity of metals is fundamentally dependent on the local electronic structure generally tailored by atomic compositions and configurations during the synthesis.Herein,we demonstrate that Cu,which is inert for oxygen reduction reaction(ORR)due to the fully occupied d-orbital,could be activated by applying a visible-light irradiation at ambient temperature.The ORR current is increased to 3.3 times higher in the potential range between-0.1 and 0.4 V under the light of 400 mW·cm^-2,and the activity enhancement is proportional to the light intensity.Together with the help of the first-principle calculation,the remarkably enhanced electrocatalytic activity is expected to stem mainly from the decreased metal-adsorbate binding by photoexcita-tion.This finding provides an additional degree of freedom for controlling and manipulating the surface reactivity of metal catalysts besides materials strategy.

Far-from-equilibrium electrosynthesis ramifies high-entropy alloy for alkaline hydrogen evolution

High-entropy alloys(HEAs)provide an ideal platform for developing highly active electrocatalysts and investigating the synergy of mixed elements.Far-from-equilibrium synthesis holds great potential for fabricating HEAs at the nanoscale by rapidly shifting the thermodynamic conditions and manipulat-ing the growth kinetics.While far-from-equilibrium synthesis of nanomaterials has been successful un-der thermochemical conditions,it is markedly challenging under electrochemical environments,as the use of an electrolyte limits the accessible temperature window and the temporal tunability of tem-perature.Herein,we demonstrate that applying a large electrochemical overpotential would create a far-from-equilibrium condition as changing the temperature of the system by considering the equation △G=△H−T△S+nF△ψ.An electrochemical far-from-equilibrium approach is thus setup for construct-ing hierarchical and self-supporting high-entropy alloy nanostructures.The large overpotential drives the simultaneous reduction of multiple cations and the subsequent formation of a single-phase alloy.As a proof-of-concept,hierarchical Fe_(0.22)Co_(0.18)Ni_(0.18)Cr_(0.14)Cu_(0.28)was fabricated and used as an electrocatalyst for the hydrogen evolution reaction in alkaline media.The noble-metal-free HEA exhibits an overpoten-tial of 84 mV at a current density of 10 mA cm^(-2),which is among the lowest even compared to noble metal-based electrocatalysts.This work opens a new avenue for building a variety of HEAs for energy and catalysis applications.

Oxygen promoted hydrogen production from formaldehyde reforming with oxide-derived Cu nanowires at room temperature

This work demonstrates a two-step method to produce oxide-derived Cu nanowires on Cu mesh surface to offer a monolithic catalyst that outstandingly improves the hydrogen production from reforming formaldehyde and water under ambient conditions.Our results not only reveal that the special oxidederived nanostructure can significantly improve the formaldehyde reforming performance of Cu,but also display that the hydrogen production has a linear relationship with oxygen pressure.Specially,a maximum of 36 times increment in hydrogen generation rate is observed than that without oxygen during the reaction.Density functional theory calculations show that the formaldehyde molecule is adsorbed on Cu surface only when the adsorbed oxygen is in adjacency,and hydrogen release process is the ratedetermining step.This work highlights that the activity of deliberately synthesized catalyst can further be promoted by dynamic chemical modulation of surface states during working.