Preserving Cu⁺ Active Sites through Intensified Electron Density for Sustained CO₂ Electroreduction

In the realm of CO2 electroreduction to C2 fuels and feedstocks, copper-based oxides (CuOx) stand out for their exceptional ability to adsorb *CO intermediates. A significant challenge in the use of Cu-based oxide catalysts is the electroreduction-driven transformation of Cu+ species to metallic Cu, predominantly attributed to the direct electron-mediated disruption of Cu–O bonds. Addressing this, our study introduces an approach that enhances the electron density in Cu2O through the integration of MoS2, thereby stabilizing the Cu+ species. This method mitigates the Cu–O bond attack by dispersing the excess electrons, which originate from the external electrode, within the Cu2O. Our composite material, Cu2O-MoS2, demonstrates a 1.9-fold increase in Faraday efficiency for C2H4 production (FEC2H4), achieving 23.3% at −1.3 V vs RHE, and exhibits predominant Cu+ stability compared to pure Cu2O. Both experimental and computational analyses reveal that the lower work function (WF) of MoS2, relative to Cu2O, facilitates electron transfer from MoS2 to Cu2O, consequently augmenting the electron density in Cu2O. This increased electron density provides a protective barrier against electron attacks from the external electrode on the Cu–O bond. Our findings present a strategy for enhancing Cu+ stability, thereby promoting C2H4 production. Furthermore, this research contributes a different insight into the design of selective and stable catalysts for CO2 reduction

La₂O₃ Doped Carbonaceous Microspheres: A Novel Bifunctional Electrocatalyst for Oxygen Reduction and Evolution Reactions with Ultrahigh Mass Activity

An efficient and robust bifunctional electrocatalyst for both ORR and OER is highly desired for the applications in renewable energy technologies. Here, we prepare the carbonaceous microspheres (CMSs) by a facile hydrothermal treatment of glucose precursor and then dope the CMSs with La₂O₃, resulting in a high performance bifunctional electrocatalyst of La₂O₃@CMSs. In alkaline solution, the La₂O₃@CMSs catalyzes oxygen reduction reactions (ORR) with an onset potential of 0.80 V versus RHE and an overpotential only of 600 mV to achieve a current density of 1.3 mA cm^–2. Meanwhile, oxygen evolution reaction (OER) at La₂O₃@CMSs electrode occurs at an onset potential of 1.60 V versus RHE and the overpotential is only 370 mV. Also, the as-prepared La₂O₃@CMSs exhibits high Faraday efficiency and long-term stability toward ORR and OER. Significantly, we demonstrate that La₂O₃@CMSs possesses surprisingly high mass activity, which is calculated to be 78.4 A g^–1 for ORR and 831.5 A g^–1 for OER, respectively. A potential window for ORR and OER at the modified electrode is estimated to be 0.80 V, implying a promising bifunctional electrocatalytical performance of La₂O₃@CMSs. The improvement of the bifunctional electrocatalytical activity may be due to the generation of active component of La–O and C–O at the surface and its synergistic interact with the La₂O₃@CMSs. This work not only provides a facile strategy for preparing highly efficient bifunctional electrocatalyst, but also offers an insight into the design of metal-oxides doped carbon materials for energy storage and conversion applications

Controllable Growth of CNTs on Graphene as High-Performance Electrode Material for Supercapacitors

Design and synthesis of three-dimensional (3D) structured carbon materials are crucial for achieving high-performance supercapacitors (SC) for energy storage. Here, we report the preparation of 3D architectured GN-CNT hybrid as SC electrodes. Controllable growth of carbon nanotubes on graphene sheets was realized through a facile one-pot pyrolysis strategy. The length of the carbon nanotubes could be rationally tuned by adjusting the amount of precursors. Correspondingly, the resulted GN-CNT hybrid showed adjustable electrochemical performance as an SC electrode. Importantly, the GN-CNT exhibited a high specific surface area of 903 m² g^–1 and maximum specific capacitance of 413 F g^–1 as SC electrodes at a scan rate of 5 mV s^–1 in 6 M KOH aqueous solution. This work paves a feasible pathway to prepare carbon electrode materials with favorable 3D architecture and high performance, for use in energy storage and conversion

Built-in Electric Field-Induced Work Function Reduction in C–Co₃O₄ for Efficient Electrochemical Nitrogen Reduction

Co3O4 is a highly selective catalyst for the electrochemical conversion of N2 to NH3. However, the large work function (WF) of Co3O4 leads to unsatisfactory activity. To address this issue, a strong built-in electric field (BIEF) was constructed in Co3O4 by doping C atoms (C–Co3O4) to reduce the WF for improving the electrocatalytic performance. C–Co3O4 exhibited a remarkable NH3 yield of 38.5 μg h–1 mgcat–1 and a promoted FE of 15.1% at −0.3 V vs RHE, which were 2.2 and 1.9 times higher than those of pure Co3O4, respectively. Kelvin probe force microscopy (KPFM), zeta potential, and ultraviolet photoelectron spectrometry (UPS) confirmed the formation of strong BIEF and WF reduction in C–Co3O4. Additionally, in situ Raman measurements and density functional theory (DFT) calculations revealed the relationship between BIEF and WF and provided insights into the reaction mechanism. Our work offers valuable guidance for the design and development of more efficient nitrogen reduction catalysts

Deciphering the Stability Mechanism of Cu Active Sites in CO₂ Electroreduction via Suppression of Antibonding Orbital Occupancy in the O 2p-Cu 3d Hybridization

Copper-based catalysts, hallmarked by their ideal C–C coupling energy facilitated by the symbiotic presence of Cu+ and Cu0 active sites, are poised to revolutionize the selective electrochemical reduction of CO2 to C2H4. Regrettably, these catalysts are beleaguered by the unavoidable diminution of Cu+ to Cu0 during the reaction process, resulting in suboptimal C2H4 yields. To circumvent this limitation, we have judiciously mitigated the antibonding orbital occupancy in the O 2p and Cu+ 3d hybridization by introducing Cu defects into Cu2O, thereby augmenting the Cu–O bond strength to stabilize Cu+ sites and further decipher the stabilization mechanism of Cu+. This structural refinement, illuminated by meticulous DFT calculations, fosters a heightened free energy threshold for the hydrogen evolution reaction (HER), while orchestrating a thermodynamically favorable milieu for enhanced C–C coupling within the Cu-deficient Cu2O (Cuv-Cu2O). Empirically, Cuv-Cu2O has outperformed its pure Cu2O counterpart, exhibiting a prominent C2H4/CO ratio of 1.69 as opposed to 1.01, without conceding significant ground in C2H4 production over an 8 h span at −1.3 V vs RHE. This endeavor not only delineates the critical influence of antibonding orbital occupancy on bond strength and reveals the deep mechanism about Cu+ sites but also charts a pioneering pathway in the realm of advanced materials design

Cu₂O Decorated with Cocatalyst MoS₂ for Solar Hydrogen Production with Enhanced Efficiency under Visible Light

In this work, we have prepared a <i>p</i>-type semiconductor of Cu₂O decorated with MoS₂ nanosheets as cocatalyst for efficient solar hydrogen production under visible light. Results show that Cu₂O decorated with 1.0 wt % MoS₂ presents the maximum reduction photocurrent density of 0.17 mA cm^–2, which is 7-fold higher than pristine Cu₂O. Furthermore, the as-prepared MoS₂@Cu₂O exhibits remarkable photostability with only 7% loss of its original photocurrent after 9 h of continuous work. The excellent performance of MoS₂@Cu₂O is ascribed to the introduction of active sites of MoS₂ nanosheets as cocatalyst to the surface of Cu₂O nanoparticles, which activates the photocatalyst by lowering the electrochemical proton reduction overpotential and also inhibits photoinduced corrosion during the measurement

Cu-Modified Palladium Catalysts: Boosting Formate Electrooxidation via Interfacially OH_ad-Driven H_ad Removal

Direct formate fuel cells have gained traction due to their eco-friendly credentials and inherent safety. However, their potential is hampered by the kinetic challenges of the formate oxidation reaction (FOR) on Pd-based catalysts, chiefly due to the unfavorable adsorption of hydrogen species (Had). These species clog the active sites, hindering efficient catalysis. Here, we introduce a straightforward strategy to remedy this bottleneck by incorporating Pd with Cu to expedite the removal of Pd–Had in alkaline media. Notably, Cu plays a pivotal role in bolstering the concentration of hydroxyl adsorbates (OHad) on the surface of catalyst. These OHad species can react with Had, effectively unblocking the active sites for FOR. The as-synthesized catalyst of PdCu/C exhibits a superior FOR performance, boasting a remarkable mass activity of 3.62 A mg–1. Through CO-stripping voltammetry, we discern that the presence of Cu in Pd markedly speeds up the formation of adsorbed hydroxyl species (OHad) at diminished potentials. This, in turn, aids the oxidative removal of Pd–Had, leveraging a synergistic mechanism during FOR. Density functional theory computations further reveal intensified interactions between adsorbed oxygen species and intermediates, underscoring that the Cu–Pd interface exhibits greater oxyphilicity compared to pristine Pd. In this study, we present both experimental and theoretical corroborations, unequivocally highlighting that the integrated copper species markedly amplify the generation of OHad, ensuring efficient removal of Had. This work paves the way, shedding light on the strategic design of high-performing FOR catalysts