| The photoelectrocatalytic (PEC) reduction of CO2 into high-value chemicals is beneficial in alleviating global warming and advancing a low-carbon economy. In the present study, Pt-modified reduced graphene oxide (Pt-RGO) and Pt-modified TiO2 nanotubes (Pt-TNT) were combined as cathode and photoanode catalysts, respectively, to form a PEC reactor for synergistic CO2 reduction. The reduced energy consumption in the PEC cell was revealed by anode photovoltage compensation on cathode CO2 reduction potential. Copper foam was used as CO2 reduction electrode and the matrix of Pt-RGO catalysts, which significantly increased carbon atom conversion rate of CO2 reduction.CO2 reduction was achieved with low energy consumption in the PEC cell which combined a Pt-RGO electrocathode and a Pt-TNT photoanode. Carbon atom conversion rate on Pt-RGO was much higher than that on Pt-modified CNT and Pt-modified active carbon, respectively. The outstanding catalytic activity of Pt-RGO was mainly attributed to its high reactant adsorptivity and efficient charge transportation. The significantly high specific surface area of RGO provided a large number of adsorption sites for the reactants. The extremely high electron transport mobility of RGO facilitated the fast reactions of electrons, protons, and CO2. Photoanode played a dual role during CO2 reduction:(1) anode photovoltage compensated and conferred more negative cathode potential for CO2 reduction; and (2) anode water decomposition provided protons and electrons for cathode CO2 reduction. Anode photovoltage compensation on cathode potential resulted in a more negative cathode potential with the same energy consumption in the PEC cell. A synergistic effect between photocatalytic and electrocatalytic reduction of CO2 was achieved. Carbon atom conversion rate initially increased and then decreased with increasing Pt loading amount on TNT, increasing Pt-RGO reduction time, increasing voltage, increasing electrolyte pH, and decreasing nickel foam pore size. Under optimum conditions, carbon atom conversion rate reached 1500 nmol/(h cm2).Cu foam combined with Pt-modified reduced graphene oxide (Pt-RGO) was investigated as an efficient cathode for CO2 reduction for the first time. Cu foam played a dual role in CO2 synergistic reduction on Pt-RGO/Cu foam, i.e., as cathode electrode and Pt-RGO catalyst matrix. Copper foam significantly suppressed hydrogen evolution and promoted CO2 reduction because of its affinity for CO2 reduction to hydrocarbons. The well-defined porosity, large specific surface area and excellent electrical conductivity made copper foam a perfect catalyst matrix. A synergistic effect of CO2 reduction on Cu foam elecrode and Pt-RGO catalysts was achieved. Carbon atom conversion rate on Pt-RGO/CF was 1.9 times of the simple addition on Pt-RGO and copper foam. Carbon atom conversion rate initially increased and then decreased with increasing applied voltage, increasing Pt loading amount on RGO, and increasing Pt-RGO loading amount on Cu foam. Under optimum conditions, carbon atom conversion rate reached 4340 nmol/(h cm2).A nanostructured Pt/graphene aerogel directly deposited in Cu foam (Pt-GA-CF) was prepared for the first time and used as a 3D binder-free cathode to convert CO2 into liquid chemicals. The uniform dispersion of Pt/GA catalysts on Cu foam facilitated electron transfer velocity on the electrode and decreased charge transfer resistance. The coating of Pt/GA on CF without any polymer binder effectively reduced contact resistance between catalysts and the current collector, which further increased the electrical properties of the electrode. The nanostructured Pt/GA without agglomeration can provide abundant adsorption sites for reactants and intermediates involved in CO2 reduction, which would facilitate CO2 conversion and the further reduction of the intermediates. The enhanced properties of Pt-GA-CF electrode markedly increased the carbon atom conversion rate of CO2 reduction which reached 5040 nmol/(h cm2). |
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