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Challenges in direct catalytic oxidation of biomass-derived aldehyde and alcohol into acid with high activity and selectivity hinder the widespread biomass application. Herein, we demonstrate that a Pd/Ni(OH)2 catalyst with abundant Ni2+-O-Pd interfaces allows electrooxidation of 5-hydroxymethylfurfural to 2, 5-furandicarboxylic acid with a selectivity near 100 % and 2, 5-furandicarboxylic acid yield of 97.3% at 0.6 volts (versus a reversible hydrogen electrode) in 1 M KOH electrolyte under ambient conditions. The rate-determining step of the intermediate oxidation of 5-hydroxymethyl-2-furancarboxylic acid is promoted by the increased OH species and low C–H activation energy barrier at Ni2+-O-Pd interfaces. Further, the Ni2+-O-Pd interfaces prevent the agglomeration of Pd nanoparticles during the reaction, greatly improving the stability of the catalyst. In this work, Pd/Ni(OH)2 catalyst can achieve 100% 5-hydroxymethylfurfural conversion and >90% 2, 5-furandicarboxylic acid selectivity in a flow-cell and work stably over 200 h under a fixed cell voltage of 0.85 V. Catalytic oxidation of biomass-derived aldehydes and alcohols into acids is challenging due to low activity and selectivity. Here the authors report a Pd/Ni(OH)2 electrocatalyst with abundant Ni2+-O-Pd interfaces that enables efficient electrooxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid with high selectivity and product yield. [ABSTRACT FROM AUTHOR]

Surface and interface engineering, especially the creation of abundant Cu 0 /Cu + interfaces and nanograin boundaries, is known to facilitate C 2+ production during electrochemical CO 2 reductions over copper-based catalysts. However, precisely controlling the favorable nanograin boundaries with surface structures (e.g., Cu(100) facets and Cu[ n (100)×(110)] step sites) and simultaneously stabilizing Cu 0 /Cu + interfaces is challenging, since Cu + species are highly susceptible to be reduced into bulk metallic Cu at high current densities. Thus, an in-depth understanding of the structure evolution of the Cu-based catalysts under realistic CO 2 RR conditions is imperative, including the formation and stabilization of nanograin boundaries and Cu 0 /Cu + interfaces. Herein we demonstrate that the well-controlled thermal reduction of Cu 2 O nanocubes under a CO atmosphere yields a remarkably stable Cu 2 O-Cu nanocube hybrid catalyst (Cu 2 O(CO)) possessing a high density of Cu 0 /Cu + interfaces, abundant nanograin boundaries with Cu(100) facets, and Cu[ n (100)×(110)] step sites. The Cu 2 O(CO) electrocatalyst delivered a high C 2+ Faradaic efficiency of 77.4% (56.6% for ethylene) during the CO 2 RR under an industrial current density of 500 mA/cm 2 . Spectroscopic characterizations and morphological evolution studies, together with in situ time-resolved attenuated total reflection-surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) studies, established that the morphology and Cu 0 /Cu + interfacial sites in the as-prepared Cu 2 O(CO) catalyst were preserved under high polarization and high current densities due to the nanograin-boundary-abundant structure. Furthermore, the abundant Cu 0 /Cu + interfacial sites on the Cu 2 O(CO) catalyst acted to increase the *CO adsorption density, thereby increasing the opportunity for C-C coupling reactions, leading to a high C 2+ selectivity.

Metal-oxide interfaces on Cu-based catalysts play very important roles in the low-temperature water-gas shift reaction (LT-WGSR). However, developing catalysts with abundant, active, and robust Cu-metal oxide interfaces under LT-WGSR conditions remains challenging. Herein, we report the successful development of an inverse copper-ceria catalyst (Cu@CeO 2 ), which exhibited very high efficiency for the LT-WGSR. At a reaction temperature of 250 °C, the LT-WGSR activity of the Cu@CeO 2 catalyst was about three times higher than that of a pristine Cu catalyst without CeO 2 . Comprehensive quasi-in situ structural characterizations indicated that the Cu@CeO 2 catalyst was rich in CeO 2 /Cu 2 O/Cu tandem interfaces. Reaction kinetics studies and density functional theory (DFT) calculations revealed that the Cu + /Cu 0 interfaces were the active sites for the LT-WGSR, while adjacent CeO 2 nanoparticles play a key role in activating H 2 O and stabilizing the Cu + /Cu 0 interfaces. Our study highlights the role of the CeO 2 /Cu 2 O/Cu tandem interface in regulating catalyst activity and stability, thus contributing to the development of improved Cu-based catalysts for the LT-WGSR.

The electrocatalytic CO 2 reduction reaction (CO 2 RR) is an attractive technology for CO 2 valorization and high-density electrical energy storage. Achieving a high selectivity to C 2+ products, especially ethylene, during CO 2 RR at high current densities (>500 mA cm -2 ) is a prized goal of current research, though remains technically very challenging. Herein, it is demonstrated that the surface and interfacial structures of Cu catalysts, and the solid-gas-liquid interfaces on gas-diffusion electrode (GDE) in CO 2 reduction flow cells can be modulated to allow efficient CO 2 RR to C 2+ products. This approach uses the in situ electrochemical reduction of a CuO nanosheet/graphene oxide dots (CuOC(O)) hybrid. Owing to abundant CuOC interfaces in the CuOC(O) hybrid, the CuO nanosheets are topologically and selectively transformed into metallic Cu nanosheets exposing Cu(100) facets, Cu(110) facets, Cu[n(100) × (110)] step sites, and Cu + /Cu 0 interfaces during the electroreduction step, the faradaic efficiencie (FE) to C 2+ hydrocarbons was reached as high as 77.4% (FE ethylene  ≈ 60%) at 500 mA cm -2 . In situ infrared spectroscopy and DFT simulations demonstrate that abundant Cu + species and Cu 0 /Cu + interfaces in the reduced CuOC(O) catalyst improve the adsorption and surface coverage of *CO on the Cu catalyst, thus facilitating CC coupling reactions., (© 2023 Wiley-VCH GmbH.)

The development of single-atom catalysts with effective interfaces for biomass conversion is a promising but challenging research area. In this study, a Ru 1 /CoO x catalyst was successfully fabricated with the impregnation method, which featured Ru single atoms on a cobalt oxide substrate. The Ru 1 /CoO x catalyst showed superior performance in the selective electrooxidation of 5-hydroxymethylfurfural (HMF) to produce 2,5-furandicarboxylic acid (FDCA), a high value-added product. The introduction of Ru single atoms with an ultralow loading of ∼0.5 wt % was revealed to accelerate the electroredox of Co 2+ /Co 3+ /Co 4+ and improve the intrinsic activity of the CoO x substrate with an FDCA selectivity of 76.5%, which is better than that of the pristine CoO x electrocatalysts (62.7%). The interfacial synergistic effect of the Ru 1 /CoO x interface clarified that Ru single atoms can enhance the adsorption of HMF at the Ru 1 /CoO x interface, which promoted the rate-determining step of the selective C-H bond activation for FDCA production. This finding provides valuable insights into the rational design of single-atom catalysts with functional interfaces for biomass upgrading.

In certain metalloenzymes, multimetal centers with appropriate primary/secondary coordination environments allow carbon-carbon coupling reactions to occur efficiently and with high selectivity. This same function is seldom realized in molecular electrocatalysts. Herein we synthesized rod-shaped nanocatalysts with multiple copper centers through the molecular assembly of a triphenylphosphine copper complex (CuPPh). The assembled molecular CuPPh catalyst demonstrated excellent electrochemical CO 2 fixation performance in aqueous solution, yielding high-value C 2+ hydrocarbons (ethene) and oxygenates (ethanol) as the main products. Using density functional theory (DFT) calculations, in situ X-ray absorption spectroscopy (XAS) and quasi- in situ X-ray photoelectron spectroscopy (XPS), and reaction intermediate capture, we established that the excellent catalytic performance originated from the large number of double copper centers in the rod-shaped assemblies. Cu-Cu distances in the absence of CO 2 were as long as 7.9 Å, decreasing substantially after binding CO 2 molecules indicating dynamic and cooperative function. The double copper centers were shown to promote carbon-carbon coupling via a CO 2 transfer-coupling mechanism involving an oxalate (OOC-COO) intermediate, allowing the efficient production of C 2+ products. The assembled CuPPh nanorods showed high activity, excellent stability, and a high Faradaic efficiency (FE) to C 2+ products (65.4%), with performance comparable to state-of-the-art copper oxide-based catalysts. To our knowledge, our findings demonstrate that harnessing metalloenzyme-like properties in molecularly assembled catalysts can greatly improve the selectivity of CO2RR, promoting the rational design of improved CO2 reduction catalysts.

The Cu + /Cu 0 interface in the Cu-based electrocatalyst is essential to promote the electrochemical reduction of carbon dioxide (ERCO 2 ) to produce multi-carbon hydrocarbons and alcohols with high selectivity. However, due to the high activity of the Cu + /Cu 0 interface, it is easy to be oxidized in the air. How to control and prepare a Cu-based electrocatalyst with an abundant and stable Cu + /Cu 0 interface in situ is a huge challenge. Here, combined with density functional theory (DFT) calculations and experimental studies, we found that the trace halide ions adsorbed on Cu 2 O can slow the reduction kinetics of Cu + → Cu 0 , which allowed us to in-situ well control the synthesis of the CuO-derived electrocatalyst with rich Cu + /Cu 0 interfaces. Our Cu catalyst with a rich Cu + /Cu 0 interface exhibits excellent ERCO 2 performance. Under the operation potential of -0.98 V versus RHE, the Faraday efficiency of C 2 H 4 and C 2+ products are 55.8 and 75.7%, respectively, which is about 16% higher than that of CuO-derived electrocatalysts that do not use halide ions. The high F E C 2 + comes from the improvement of the coupling efficiency of reaction intermediates such as CO-CO, which is proved by DFT calculations, and the suppression of hydrogen evolution reaction. Therefore, we provide an in-situ engineering strategy, which is simple and effective for the design and preparation of high-performance ERCO 2 catalysts.