The electrochemical reduction of CO2 to fuels and value-added chemicals on metallic copper is an attractive strategy for valorizing CO2 emissions. However, favoring the CO2 reduction over hydrogen ...evolution and exclusive control of selectivity towards C1 or C2+ products by restructuring the copper surface is a major challenge. Herein, we exploit the differential orientation of the exposed facets in copper nanostructures that can tune the product selectivity in CO2 electroreduction. The Cu nanostructure with predominant {111} orientation produce C1 products only upon CO2 electroreduction at an applied potential of −1.3 V vs. reversible hydrogen electrodes (RHE), with 66.57% Faradaic efficiency (FE) for methane. Whereas the vertically grown copper nanostructures that are oriented in {110} direction have higher dislocation density and show greater CO2 electroreduction activity (>95%) at the same applied potential, with FE towards ethylene 24.39% and that of oxygenates 41.31%. FIA-DEMS analysis provided experimental evidence of selectivity of methane over methanol at higher overpotentials indicating the mechanism of methane formation occurs via *COH intermediate. The ethylene formation at a potential −1.0 V vs. RHE or more negative to it suggests a common intermediate for methane and ethylene on the vertically grown copper nanostructures. This work advances the understanding between the product selectivity and the surface structure of the copper nanostructures in electrochemical CO2 reduction.
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•Growth direction of copper nanostructures determine the facet formation on the surface.•Higher dislocation density on Cu NsB favored CO2 reduction suppressing H2 evolution.•Cu NsA produced C1 products only on CO2 electroreduction with CH4 as the major product.•The local pH effect on the copper nanostructure is influenced by its exposed facets.•DEMS analysis shows selectivity of methane over methanol at higher overpotentials.
Sodium niobate nanorods (SNRs) have been synthesized by a facile surfactant free hydrothermal method. To explore their potential for photoelectrochemical water splitting under visible light, ...core-shell nanorods were fabricated by grafting CdS on sodium niobate nanorods. The TEM analysis shows the formation of sodium niobate nanorods which are in the order of 40 plus or minus 5 nm in width and 1300 plus or minus 100 nm in length. The presence of a thin layer on nanorods, as observed in a TEM image, and XRD and SAD analysis, reveals the grafting of hexagonal CdS on orthorhombic sodium niobate nanorods. This was further confirmed by dual band gap values (E sub(g): 3.6 for sodium niobate and 2.59 eV for CdS) determined from diffuse reflectance data of the CdS-sodium niobate nanorod sample. The CdS-sodium niobate nanorods show drastic enhancement in the current density (J sub(an): 7.6 mA cm super(-2) at 0.2 V vs.SHE) when irradiated with monochromatic UV light (300 nm), many folds higher than that observed for bare sodium niobate nanorods (J sub(an): 2.5 mA cm super(-2) at 0.2 V vs.SHE), bulk sodium niobate (J sub(an): 0.6 mA cm super(-2) at 0.2 V vs.SHE) and CdS. The conduction band (CB) minima calculations show a downhill offset of the CB edges of CdS-sodium niobate. Such a downhill staggered band gap and smooth lattice matched interface, as shown by HRTEM, seem to facilitate an efficient charge separation followed by a photo-generated e super(-) transfer from the CdS CB to the sodium niobate CB and, therefore, appear responsible for the enhancement of the photocurrent density of CdS-sodium niobate nanorods. This is further corroborated by the time resolved photoluminescence decay measurements which show a longer average decay time (< tau >) for CdS-sodium niobate nanorods in the order of 8.06 ns than that for sodium niobate nanorods (6.45 ns). Furthermore, better light harvesting efficiency and incident to photon conversion efficiency (23.91% at 300 nm) observed for CdS-sodium niobate nanorods imply a better photo-generated charge carrier separation than those observed for bare sodium niobate nanorods and bulk sodium niobate. The synthesis of CdS modified sodium niobate nanorods, detailed results on the photoelectrochemical behaviour of CdS modified sodium niobate nanorods and underlying mechanism are presented.
Developing copper‐based electrocatalysts that favor high‐value multi‐carbon oxygenates is desired, given their use as platform chemicals and as a direct fuel for transportation. Combining a ...CO‐selective catalyst with copper shifts the selectivity of CO2 electroreduction toward C2 products. Herein, we developed a reduced graphene oxide (rGO)‐modified copper nanocube electrocatalyst that could shift the selectivity of CO2 electroreduction towards ethanol (Faradaic efficiency 76. 84 % at −0.9 V vs. reversible hydrogen electrode (RHE)). Spectroelectrochemical Raman analysis reveals a higher population of *C2HxOy intermediates at −0.9 V vs. RHE on the rGO‐modified copper nanocube electrocatalyst surface, which coincides with the highest faradaic efficiency of ethanol upon CO2 electroreduction at the same potential. Our results demonstrate that the rGO modification can enhance ethanol selectivity through a probable tandem electrocatalysis mechanism and provide insights into controlling electrocatalytic activity and product selectivity in the CO2 electroreduction reaction.
Tandem electrocatalysis enhances ethanol selectivity in CO2 electroreduction: The modification of copper nanocubes by reduced graphene oxide (rGO) led to superior ethanol selectivity in the electrochemical CO2 reduction. High Faradaic efficiency was achieved due to the CO‐rich environment at the rGO−copper interface, increasing the coverage of *CO on the Cu surface that could lower the barrier to C−C coupling and steer the selectivity towards ethanol formation via tandem electrocatalysis.
