Electrochemical Carbon Dioxide Reduction to Ethylene:From Mechanistic Understanding to Catalyst Surface Engineering

Electrochemical carbon dioxide reduction reaction(CO_(2)RR)provides a promising way to convert CO_(2)to chemicals.The multicarbon(C_(2+))products,especially ethylene,are of great interest due to their versatile industrial applications.However,selectively reducing CO_(2)to ethylene is still challenging as the additional energy required for the C–C coupling step results in large overpotential and many competing products.Nonetheless,mechanistic understanding of the key steps and preferred reaction pathways/conditions,as well as rational design of novel catalysts for ethylene production have been regarded as promising approaches to achieving the highly efficient and selective CO_(2)RR.In this review,we first illustrate the key steps for CO_(2)RR to ethylene(e.g.,CO_(2)adsorption/activation,formation of~*CO intermediate,C–C coupling step),offering mechanistic understanding of CO_(2)RR conversion to ethylene.Then the alternative reaction pathways and conditions for the formation of ethylene and competitive products(C_1 and other C_(2+)products)are investigated,guiding the further design and development of preferred conditions for ethylene generation.Engineering strategies of Cu-based catalysts for CO_(2)RR-ethylene are further summarized,and the correlations of reaction mechanism/pathways,engineering strategies and selectivity are elaborated.Finally,major challenges and perspectives in the research area of CO_(2)RR are proposed for future development and practical applications.

Recent advances in p-block metal chalcogenide electrocatalysts for high-efficiency CO_(2) reduction

Electrocatalytic CO_(2) reduction(ECR)to high-value fuels and chemicals offers a promising conversion technology for achieving sustainable carbon cycles.In recent years,although great efforts have been made to develop highefficiency ECR catalysts,challenges remain in achieving high activity and long durability simultaneously.Taking advantage of the adjustable structure,tunable component,and the M–Ch(M¼Sn,In,Bi,etc.,Ch¼S,Se,Te)covalent bonds stabilized metal centers,the p-block metal chalcogenides(PMC)based electrocatalysts have shown great potential in converting CO_(2) into CO or formates.In addition,the unique p-block electron structure can suppress the competitive hydrogen evolution reaction and enhance the adsorption of ECR intermediates.Seeking to systematically understand the structure–activity relationship of PMC-based ECR catalysts,this review summarizes the recent advances in designing PMC electrocatalysts for CO_(2) reduction based on the fundamental aspects of heterogeneous ECR process,including advanced strategies for optimizing the intrinsic activity and improving the loading density of catalytic sites,constructing highly stable catalysts,and tuning product.

Insights into the Dynamic Surface Reconstruction of Electrocatalysts in Oxygen Evolution Reaction

Electrocatalytic water splitting,which is recognized as an ideal technology to tackle escalating energy demands and related environmental problems,has attracted growing interest.The sluggish dynamics of the oxygen evolution reaction(OER)has posed an intractable problem in this regard,hindering the practical commercial application of hydrogen production via water splitting.Therefore,the development of active and stable electrocatalysts is a prerequisite for accelerating OER kinetics,which greatly relies on the mechanistic understanding of the structural-property relationship.Owing to the harsh anodic oxidation conditions,most of the catalysts undergo surface reconstruction during the OER process,which means the authentic active sites are the in-situ reconstructed species rather than the freshly prepared one.In this regard,fully comprehending the surface reconstruction process will help us to determine the active sites on the catalyst surface and gain insights into the design principles for more efficient OER catalysts.In this review,we will first give a summary of surface reconstruction of OER electrocatalysts.Then we will focus on the factors that affect surface reconstruction,in-situ/operando characterization technologies,and the strategies to govern surface reconstruction.In addition,we outline existing challenges and the outlook for the development of OER catalysts by tuning surface reconstruction.

Electrocatalytic oxidation of 5-hydroxymethylfurfural for sustainable 2,5-furandicarboxylic acid production-From mechanism to catalysts design

Catalytic conversion of biomass-based platform chemicals is one of the significant approaches to utilize renewable biomass resources.2,5-Furandicarboxylic acid(FDCA),obtained by an electrocatalytic oxidation of 5-hydroxymethylfurfural(HMF),has attracted extensive attention due to the potential of replacing terephthalic acid to synthesize high-performance polymeric materials for commercialization.In the present work,the pHdependent reaction pathways and factors influencing the degree of functional group oxidation are first discussed.Then the reaction mechanism of HMF oxidation is further elucidated using the representative examples.In addition,the emerging catalyst design strategies(defects,interface engineering)used in HMF oxidation are generalized,and structure-activity relationships between the abovementioned strategies and catalysts performance are analyzed.Furthermore,cathode pairing reactions,such as hydrogen evolution reaction,CO_(2) reduction reaction(CO_(2)RR),oxygen reduction reaction,and thermodynamically favorable organic reactions to lower the cell voltage of the electrolysis system,are discussed.Finally,the challenges and prospects of the electrochemical oxidation of HMF for FDCA are presented,focusing on deeply investigated reaction mechanism,coupling reaction,reactor design,and downstream product separation/purification.

Designing Electrocatalysts for High-Current-Density Freshwater/Seawater Splitting

Electrocatalytic water splitting is crucial to renewable and clean hydrogen generation.Achieving high efficiency and stability in hydrogen generation by freshwater/seawater electrolysis at a high current density(HCD)using low-cost electrode materials is of utmost importance for the future hydrogen economy.However,conventional freshwater/seawater electrolysis suffers from low current density due to inefficient electrocatalysts and competitive reactions of the chlorine evolution reaction(ClER),consequently hampering its industrial adoption.Advanced surface and interface engineering techniques are essential for the development of efficient and long-lasting electrodes for freshwater and seawater electrolysis at HCD.In the review,we begin by discussing the fundamental aspects of freshwater/seawater splitting,focusing on recent advancements and strategies to increase the efficiency at HCD.We then comprehensively discuss the rational design strategies for the hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)at HCD together with the associated fundamental electrode reactions by considering the thermodynamic and kinetic aspects of the catalytic efficiency,selectivity,and corrosion resistance.It is followed by a discussion of some existing issues and limitations of HCD freshwater/seawater splitting and viable solutions.Finally,the issues facing the field and possible future research directions for efficient large-scale industrial water splitting are discussed.