An efficient chamber-induced activation method was applied for the preparation of holey graphene/cellulose nanofiber-based film with high specific surface area(SSA)and multiple channels through the graphene nanosheets...An efficient chamber-induced activation method was applied for the preparation of holey graphene/cellulose nanofiber-based film with high specific surface area(SSA)and multiple channels through the graphene nanosheets.With the cellulose nanofiber(CNF)simultaneously serving as“dispersing agent,”“spacer,”and“activating agent,”the graphene oxide(GO)nanosheets are perforated by the pyrolysis gas from CNF in the confined space inside the hybrid films,uniformly dispersed,and sandwiched between CNF networks with less agglomeration and restacking.Additionally,we have proved that H2O and H2 are primarily responsible for the activation and etching of GO/CNF film.As the CNF content increases,the mesoporosity of the activated reduced GO/CNF(A-RGO/CNF)film increases,and the graphene nanosheets show more nanopore perforations.Benefitting from the high SSA,high density,moderate mesoporosity,and abundant channels for ion diffusion through the graphene nanosheets,the A-RGO/CNF film exhibits the highest specific capacitance of 323(236)F g^(−1)(F cm^(−3))at 1Ag^(−1).For the A-RGO5/CNF5 film containing half CNF and half GO,an excellent comprehensive electrochemical performance including superior rate performance(208(160)F g^(−1)(F cm^(−3))at 60Ag^(−1))is exhibited.Moreover,the A-RGO5/CNF5 electrode in an all-solid-state flexible symmetric supercapacitor delivers a high specific capacitance of 250(193)F g^(−1)(F cm^(−3))at 1Ag^(−1).This study provides a novel idea for the preparation of holey graphene-based film for supercapacitor electrodes.The strategy of simultaneously employing CNF as“dispersing agent,”“spacer,”and“activating agent”also offers a new vision for the assembly of homogeneous nanohybrid material and the utilization of pyrolysis gas.展开更多
CO_(x)(x=1,2)and O_(2) chemistry play key roles in tackling global severe environmental challenges and energy issues.To date,the efficient selective electrocatalytic transformations of COx-carbon chemicals,and O_(2)-h...CO_(x)(x=1,2)and O_(2) chemistry play key roles in tackling global severe environmental challenges and energy issues.To date,the efficient selective electrocatalytic transformations of COx-carbon chemicals,and O_(2)-hydrogenated products are still huge challenges.Single-atom catalysts(SACs)as atomic-scale novel catalysts in which only isolated metal atoms are dispersed on supports shed new insights in overcome these obstacles in CO_(x) and O_(2) chemistry,including CO oxidation,CO_(2) reduction reaction(CO_(2)RR),oxygen reduction reaction(ORR),and oxygen evolution reaction(OER).In this review,the unique features and advanced synthesis strategies of SACs from a viewpoint of fundamental synthesis design are first highlighted to guide future strategy design for controllable SAC synthesis.Then,the to-date reported CO_(2)RR,CO oxidation,OER,and ORR mechanism are included and summarized.More importantly,the design principles and design strategies of improving the intrinsic activity,selectivity,and stability are extensively discussed and the engineering strategy is classified as neighbor coordination engineering,metal-atom engineering,and substrate engineering.Via the comprehensive review and summary of state-of-the-art SACs,the synthesis–structure–property–mechanism–design principle relation can be revealed to shed lights into the structural construction of SACs.Finally,we present an outlook on current challenges and future directions for SACs in CO_(x) and O_(2) chemistry.展开更多
Photoelectrochemical devices have been developed to enable the conversion of solar energy.However,their commercial potential is restricted by the limited stability of the materials employed.To enhance the stability of...Photoelectrochemical devices have been developed to enable the conversion of solar energy.However,their commercial potential is restricted by the limited stability of the materials employed.To enhance the stability of photocathode and its solar water splitting performance,a P-Si/TiO_(2)/HfO_(2)/MoS_(2)/Pt composite photocathode is developed in this work.The novel TiO_(2)/HfO_(2)/MoS_(2) serial nanostructure provides excellent stability of the photocathode,and optimizes the interface energy barrier to further facilitate the transfer process of photogenerated carriers within the photocathode.The best P-Si/TiO_(2)/HfO_(2)/MoS_(2)/Pt photocathode demonstrates an initial potential of 0.5 V(vs.RHE)and a photocurrent density of-29 mA/cm^(2) at 0 V(vs.RHE).Through intensity modulated photocurrent spectroscopy and photoluminescence test,it is known that the enhanced water splitting performance is attributed to the optimized carrier transfer property.These findings provide a feasible strategy for the stability and photon quantum efficiency enhancement of silicon-based photocathode devices.展开更多
基金funded by the Ministry of Business,Innovation and Employment Endeavour Fund of New Zealand(MAUX1801)supported by the China Postdoctoral Science Foundation(2021M692622).
文摘An efficient chamber-induced activation method was applied for the preparation of holey graphene/cellulose nanofiber-based film with high specific surface area(SSA)and multiple channels through the graphene nanosheets.With the cellulose nanofiber(CNF)simultaneously serving as“dispersing agent,”“spacer,”and“activating agent,”the graphene oxide(GO)nanosheets are perforated by the pyrolysis gas from CNF in the confined space inside the hybrid films,uniformly dispersed,and sandwiched between CNF networks with less agglomeration and restacking.Additionally,we have proved that H2O and H2 are primarily responsible for the activation and etching of GO/CNF film.As the CNF content increases,the mesoporosity of the activated reduced GO/CNF(A-RGO/CNF)film increases,and the graphene nanosheets show more nanopore perforations.Benefitting from the high SSA,high density,moderate mesoporosity,and abundant channels for ion diffusion through the graphene nanosheets,the A-RGO/CNF film exhibits the highest specific capacitance of 323(236)F g^(−1)(F cm^(−3))at 1Ag^(−1).For the A-RGO5/CNF5 film containing half CNF and half GO,an excellent comprehensive electrochemical performance including superior rate performance(208(160)F g^(−1)(F cm^(−3))at 60Ag^(−1))is exhibited.Moreover,the A-RGO5/CNF5 electrode in an all-solid-state flexible symmetric supercapacitor delivers a high specific capacitance of 250(193)F g^(−1)(F cm^(−3))at 1Ag^(−1).This study provides a novel idea for the preparation of holey graphene-based film for supercapacitor electrodes.The strategy of simultaneously employing CNF as“dispersing agent,”“spacer,”and“activating agent”also offers a new vision for the assembly of homogeneous nanohybrid material and the utilization of pyrolysis gas.
基金supported by the National Natural Science Foundation of China(No.51632007)the National Science and Technology Major Project(2017-VI-0007-0077)。
文摘CO_(x)(x=1,2)and O_(2) chemistry play key roles in tackling global severe environmental challenges and energy issues.To date,the efficient selective electrocatalytic transformations of COx-carbon chemicals,and O_(2)-hydrogenated products are still huge challenges.Single-atom catalysts(SACs)as atomic-scale novel catalysts in which only isolated metal atoms are dispersed on supports shed new insights in overcome these obstacles in CO_(x) and O_(2) chemistry,including CO oxidation,CO_(2) reduction reaction(CO_(2)RR),oxygen reduction reaction(ORR),and oxygen evolution reaction(OER).In this review,the unique features and advanced synthesis strategies of SACs from a viewpoint of fundamental synthesis design are first highlighted to guide future strategy design for controllable SAC synthesis.Then,the to-date reported CO_(2)RR,CO oxidation,OER,and ORR mechanism are included and summarized.More importantly,the design principles and design strategies of improving the intrinsic activity,selectivity,and stability are extensively discussed and the engineering strategy is classified as neighbor coordination engineering,metal-atom engineering,and substrate engineering.Via the comprehensive review and summary of state-of-the-art SACs,the synthesis–structure–property–mechanism–design principle relation can be revealed to shed lights into the structural construction of SACs.Finally,we present an outlook on current challenges and future directions for SACs in CO_(x) and O_(2) chemistry.
基金supported by the Key projects of intergovernmental international cooperation in key R&D programs of the Ministry of science and technology of China(No.2021YFE0115800)the National Science Funding Committee of China(No.U20A20250).
文摘Photoelectrochemical devices have been developed to enable the conversion of solar energy.However,their commercial potential is restricted by the limited stability of the materials employed.To enhance the stability of photocathode and its solar water splitting performance,a P-Si/TiO_(2)/HfO_(2)/MoS_(2)/Pt composite photocathode is developed in this work.The novel TiO_(2)/HfO_(2)/MoS_(2) serial nanostructure provides excellent stability of the photocathode,and optimizes the interface energy barrier to further facilitate the transfer process of photogenerated carriers within the photocathode.The best P-Si/TiO_(2)/HfO_(2)/MoS_(2)/Pt photocathode demonstrates an initial potential of 0.5 V(vs.RHE)and a photocurrent density of-29 mA/cm^(2) at 0 V(vs.RHE).Through intensity modulated photocurrent spectroscopy and photoluminescence test,it is known that the enhanced water splitting performance is attributed to the optimized carrier transfer property.These findings provide a feasible strategy for the stability and photon quantum efficiency enhancement of silicon-based photocathode devices.