Regulating local coordination environment of Mg-Co single atom catalyst for improved direct methanol fuel cell cathode

Fuel cells operated with a reformate fuel such as methanol are promising power systems for portable electronic devices due to their high safety,high energy density and low pollutant emissions.However,several critical issues including methanol crossover effect,CO-tolerance electrode and efficient oxygen reduction electrocatalyst with low or non-platinum usage have to be addressed before the direct methanol fuel cells(DMFCs)become commercially available for industrial application.Here,we report a highly active and selective Mg-Co dualsite oxygen reduction reaction(ORR)single atom catalyst(SAC)with porous N-doped carbon as the substrate.The catalyst exhibits a commercial Pt/C-comparable half-wave potential of 0.806 V(versus the reversible hydrogen electrode)in acid media with good stability.Furthermore,practical DMFCs test achieves a peak power density of over 200 m W cm^(-2)that far exceeds that of commercial Pt/C counterpart(82 m W cm^(-2)).Particularly,the Mg-Co DMFC system runs over 10 h with negligible current loss under 10 M concentration methanol work condition.Experimental results and theoretical calculations reveal that the N atom coordinated by Mg and Co atom exhibits an unconventional d-band-ditto localized p-band and can promote the dissociation of the key intermediate*OOH into*O and*OH,which accounts for the near unity selective 4e-ORR reaction pathway and enhanced ORR activity.In contrast,the N atom in SAC–Co remains inert in the absorption and desorption of*OOH and*OH.This local coordination environment regulation strategy around active sites may promote rational design of high-performance and durable fuel cell cathode electrocatalysts.

Isotype Heterojunction‑Boosted CO_(2) Photoreduction to CO

Photocatalytic conversion of CO_(2) to high-value products plays a crucial role in the global pursuit of carbon–neutral economy.Junction photocatalysts,such as the isotype heterojunctions,offer an ideal paradigm to navigate the photocatalytic CO_(2) reduction reaction(CRR).Herein,we elucidate the behaviors of isotype heterojunctions toward photocatalytic CRR over a representative photocatalyst,g-C_(3)N_(4).Impressively,the isotype heterojunctions possess a significantly higher efficiency for the spatial separation and transfer of photogenerated carriers than the single components.Along with the intrinsically outstanding stability,the isotype heterojunctions exhibit an exceptional and stable activity toward the CO_(2) photoreduction to CO.More importantly,by combining quantitative in situ technique with the first-principles modeling,we elucidate that the enhanced photoinduced charge dynamics promotes the production of key intermediates and thus the whole reaction kinetics.

Bismuth clusters pinned on TiO_(2) porous nanowires boosting charge transfer for CO_(2) photoreduction to CH_(4)

Artificial photosynthesis in carbon dioxide(CO_(2))conversion into value-added chemicals attracts considerable attention but suffers from the low activity induced by sluggish separation of photogenerated carriers and the kinetic bottleneck-induced unsatisfied selectivity.Herein,we prepare a new-style Bi/TiO_(2) catalyst formed by pinning bismuth clusters on TiO_(2) nanowires through being confined by pores,which exhibits high activity and selectivity towards photocatalytic production of CH_(4) from CO_(2).Boosted charge transfer from TiO_(2) through Bi to the reactants is revealed via in situ X-ray photon spectroscopy and time-resolved photoluminescence(PL).Further,in situ Fourier transform infrared results confirm that Bi/TiO_(2) not only overcomes the multi-electron kinetics challenge of CO_(2) to CH_(4) via boosting charge transfer,but also facilitates proton production and transfer as well as the intermediates*CHO and*CH_(3)O generation,ultimately achieving the tandem catalysis towards methanation.Theoretical calculation also underlies that the more favorable reaction step from*CO to*CHO on Bi/TiO_(2) results in CH_(4) production with higher selectivity.Our work brings new insights into rational design of photocatalysts with high performance and the formation mechanism of CO_(2) to CH_(4) for solar energy storage in future.

Interfacial Engineering of NiFeP/NiFe-LDH Heterojunction for Efficient Overall Water Splitting

In consideration of application prospect of non-noble metallic materials catalysts,the study of exploring more highly effective electrocatalysts has been focused on by researchers.Herein,a novel strategy is employed to construct a heterojunction consisting of metal phosphide Ni_(x)Fe_(y)P and layered double hydroxide(LDH)with graphene oxide(GO)as conductive support.By adjusting the molar ratio of Ni to Fe,a series of heterojunctions with mixed valence state Fe^(δ+)/Fe^(3+)and Ni^(δ+)/Ni^(2+)(δis likely close to 0)redox couples are achieved and strong synergistic effects towards overall water splitting performance are found.The optimized catalyst with a Ni/Fe molar ratio of 0.72:0.33,namely Ni_(0.7)Fe_(0.3)P/LDH/GO,delivers ultra-low overpotentials for hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)of 79 and 198 mV at the current density of 10 mA·cm^(-2),respectively.Furthermore,for overall water-splitting practical application,it only requires 1.526 V at 10 mA·cm^(-2)with robust stability,which is superior to most reported electrocatalysts.Experimental results demonstrate the im-proved electronic conductivity,enlarged electrochemically active area and accelerated kinetics together account for the enhanced performance.This work supplies new prospects for the promotion and application of such heterojunction electrocatalysts in overall water splitting.