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Pulsed CO2 electroreduction (CO2RR) has recently emerged as a facile way to in situ tune the product selectivity, in particular toward ethanol, without re-designing the catalytic system. However, in-depth mechanistic understanding requires comprehensive operando time-resolved studies to identify the kinetics and dynamics of the electrocatalytic interface. Here, we track the adsorbates and the catalyst state of pre-reduced Cu2O nanocubes (~ 30 nm) during pulsed CO2RR using sub-second time-resolved operando Raman spectroscopy. By screening a variety of product-steering pulse length conditions, we unravel the critical role of co-adsorbed OH and CO on the Cu surface next to the oxidative formation of Cu-Oad or CuOx/(OH)y species, impacting the kinetics of CO adsorption and boosting the ethanol selectivity. However, a too low OHad coverage following the formation of bulk-like Cu2O induces a significant increase in the C1 selectivity, while a too high OHad coverage poisons the surface for C-C coupling. Thus, we unveil the importance of co-adsorbed OH on the alcohol formation under CO2RR conditions and thereby, pave the way for improved catalyst design and operating conditions. Controlling the selectivity of the electroreduction of CO2 to value-added products is challenging. Here, authors use sub-second operando Raman spectroscopy to analyze Cu catalyst surfaces and discover the pivotal role of co-adsorbed OH and CO in enhancing ethanol selectivity. [ABSTRACT FROM AUTHOR]

We report the synthesis of graphene- TiO2 ( G-TiO2) composite films that exhibit significantly enhanced photoelectrochemical water-splitting performance relative to pure TiO2. Supersonic kinetic spraying was used to produce strongly adhered, electrically and mechanically robust G-TiO2 composite films containing 0.1, 0.5, 1.0, and 5.0 wt.% graphene. Films with an intermediate graphene content of 1.0 wt.% demonstrated the best water-splitting performance. G-TiO2 composite films with 1.0 wt.% graphene exhibited photocurrent density ten times that of pure TiO2 films. The electron transfer between TiO2 and graphene suppresses the recombination of photoinduced charge carriers and prolongs the electron excited-state lifetime, which contributes to the enhanced photoelectrochemical water-splitting performance. [ABSTRACT FROM AUTHOR]

This study presents the impact of the side chains in 1-n-alkylimidazolium ionomers with varying side chain lengths (C n H 2n+1 where n = 1, 4, 10, 16) on Cu-catalyzed electrochemical CO 2 reduction reaction (CO 2 RR). Longer side chains suppress the H 2 and CH 4 formation, with the n-hexadecyl ionomer (n = 16) showing the greatest reduction in kinetics by up to 56.5% and 60.0%, respectively. On the other hand, C 2 H 4 production demonstrates optimal Faradaic efficiency with the n-decyl ionomer (n = 10), a substantial increase of 59.9% compared to its methyl analog (n = 1). Through a combination of density functional theory calculations and material characterization, it is revealed that the engineering of the side chains effectively modulates the thermodynamic stability of key intermediates, thus influencing the selectivity of both CO 2 RR and hydrogen evolution reaction. Moreover, ionomer engineering enables industrially relevant partial current density of -209.5 mA cm -2 and a Faradaic efficiency of 52.4% for C 2 H 4 production at 3.95 V, even with a moderately active Cu catalyst, outperforming previous benchmarks and allowing for further improvement through catalyst engineering. This study underscores the critical role of ionomers in CO 2 RR, providing insights into their optimal design for sustainable chemical synthesis., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

Electrochemical reduction of CO 2 (CO 2 RR) is an attractive technology to reintegrate the anthropogenic CO 2 back into the carbon cycle driven by a suitable catalyst. This study employs highly efficient multi-carbon (C 2+ ) producing Cu 2 O nanocubes (NCs) decorated with CO-selective Au nanoparticles (NPs) to investigate the correlation between a high CO surface concentration microenvironment and the catalytic performance. Structure, morphology and near-surface composition are studied via operando X-ray absorption spectroscopy and surface-enhanced Raman spectroscopy, operando high-energy X-ray diffraction as well as quasi in situ X-ray photoelectron spectroscopy. These operando studies show the continuous evolution of the local structure and chemical environment of our catalysts during reaction conditions. Along with its alloy formation, a CO-rich microenvironment as well as weakened average CO binding on the catalyst surface during CO 2 RR is detected. Linking these findings to the catalytic function, a complex compositional interplay between Au and Cu is revealed in which higher Au loadings primarily facilitate CO formation. Nonetheless, the strongest improvement in C 2+ formation appears for the lowest Au loadings, suggesting a beneficial role of the Au-Cu atomic interaction for the catalytic function in CO 2 RR. This study highlights the importance of site engineering and operando investigations to unveil the electrocatalyst's adaptations to the reaction conditions, which is a prerequisite to understand its catalytic behavior., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)