Simultaneous Interface Engineering and Phase Tuning of CeO2-Decorated Catalysts for Boosted Oxygen Evolution Reaction

Heterogeneous catalysts have attracted extensive attention among various emerging catalysts for their exceptional oxygen evolution reaction (OER) capabilities, outperforming their single-component counterparts. Nonetheless, the synthesis of heterogeneous materials with predictable, precise, and facile control remains a formidable challenge. Herein, a novel strategy involving the decoration of catalysts with CeO2 is introduced to concurrently engineer heterogeneous interfaces and adjust phase composition, thereby enhancing OER performance. Theoretical calculations suggest that the presence of ceria reduces the free energy barrier for the conversion of nitrides into metals. Supporting this, the experimental findings reveal that the incorporation of rare earth oxides enables the controlled phase transition from nitride into metal, with the proportion adjustable by varying the amount of added rare earth. Thanks to the role of CeO2 decoration in promoting the reaction kinetics and fostering the formation of the genuine active phase, the optimized Ni3FeN/Ni3Fe/CeO2-5% nanoparticles heterostructure catalyst exhibits outstanding OER activity, achieving an overpotential of just 249 mV at 10 mA cm-2. This approach offers fresh perspectives for the conception of highly efficient heterogeneous OER catalysts, contributing a strategic avenue for advanced catalytic design in the field of energy conversion.

Revealing the effect of crystallinity and oxygen vacancies of Fe-Co phosphate on oxygen evolution for high-current water splitting

Strategically tuning the composition and structure of transition metal phosphates (TMPs) holds immense promise in the development of efficient oxygen evolution reaction (OER) electrocatalysts. However, the effect of crystalline phase transformation for TMPs on the catalytic OER activity remains relatively uncharted. In this study, we have deftly orchestrated the reaction process of anion-etched precursor to induce the amorphization process of FeCo-POx from crystalline to amorphous states. The as-obtained amorphous FeCo-POx (A-FeCo-POx) exhibited an optimized OER performance with a low overpotential of 270 mV at a current density of 10 mA cm-2, which could be attributed to the flexibility of its amorphous structure and the synergistic effect of oxygen vacancies. Moreover, when incorporated into an overall water splitting (OWS) device configured as A-FeCo-POx(+)||Pt/C(-), it displayed long-term solid stability, sustaining operation for 300 h at a current density of 200 mA cm-2. This work not only provides valuable insights into understanding the transformation from crystalline to amorphous states, but also establishes the groundwork for the practical utilization of amorphous nanomaterials in the field of water splitting.

Surface Enhancement Effects of Tiny SnO2 Nanoparticle Modification on α-Fe2O3 for Room-Temperature NH3 Sensing

The development of a gas sensor capable of detecting ammonia with high selectivity and rapid response at room temperature has consistently posed a formidable challenge. To address this issue, the present study utilized a one-step solvothermal method to co-assemble α-Fe2O3 and SnO2 by evenly covering SnO2 nanoparticles on the surface of α-Fe2O3. By controlling the morphology and Fe/Sn mole ratio of the composite, the as-prepared sample exhibits high-performance detection of NH3. At room temperature conditions, a gas sensor composed of α-Fe2O3@3%SnO2 demonstrates a rapid response time of 14 s and a notable sensitivity of 83.9% when detecting 100 ppm ammonia. Experiments and density functional theory (DFT) calculations suggest that the adsorption capacity of α-Fe2O3 to ammonia is enhanced by the surface effect provided by SnO2. Meanwhile, the existence of SnO2 tailors the pore structure and effective surface area of α-Fe2O3, creating multiple channels for the diffusion and adsorption of ammonia molecules. Additionally, an N-N heterostructure is formed between α-Fe2O3 and SnO2, which enhances the potential energy barrier and improves the ammonia sensing performance. Demonstration experiments have proved that the sensor shows significant advantages over commercial sensors in the process of ammonia detection in agricultural facilities. This work provides new insights into the perspectives on ammonia detection at room temperature.

Heterostructure Interface Engineering in CoP/FeP/CeOx with a Tailored d-Band Center for Promising Overall Water Splitting Electrocatalysis

Accomplishing a green hydrogen economy in reality through water spitting ultimately relies upon earth-abundant efficient electrocatalysts that can simultaneously accelerate the oxygen and hydrogen evolution reactions (OER and HER). The perspective of electronic structure modulation via interface engineering is of great significance to optimize electrocatalytic output but remains a tremendous challenge. Herein, an efficient tactic has been explored to prepare nanosheet-assembly tumbleweed-like CoFeCe-containing precursors with time-/energy-saving and easy-operating features. Subsequently, the final metal phosphide materials containing multiple interfaces, denoted CoP/FeP/CeO_x, have been synthesized via the phosphorization process. Through the optimization of the Co/Fe ratio and the content of the rare-earth Ce element, the electrocatalytic activity has been regulated. As a result, bifunctional Co3Fe/Ce0.025 reaches the top of the volcano for both OER and HER simultaneously, with the smallest overpotentials of 285 mV (OER) and 178 mV (HER) at 10 mA cm^-2 current density in an alkaline environment. Multicomponent heterostructure interface engineering would lead to more exposed active sites, feasible charge transport, and strong interfacial electronic interaction. More importantly, the appropriate Co/Fe ratio and Ce content can synergistically tailor the d-band center with a downshift to enhance the per-site intrinsic activity. This work would provide valuable insights to regulate the electronic structure of superior electrocatalysts toward water splitting by constructing rare-earth compounds containing multiple heterointerfaces.

Engineered Superhydrophilic/Superaerophobic Catalyst: Two-Dimensional Co(OH)2-CeO2 Nanosheets Supported on Three-Dimensional Co Dendrites for Overall Water Splitting

Efficient electrocatalysts require not only a tunable electronic structure but also great active site accessibility and favorable mass transfer. Here, a two-dimensional/three-dimensional (2D/3D) hierarchical electrocatalyst consisting of Co(OH)₂-CeO₂ nanosheet-decorated Co dendrites is proposed, named as Co(OH)₂-CeO₂/Co. Based on the strong electronic interaction of the Co(OH)₂-CeO₂ heterojunction, the electronic structure of the Co site is optimized, which facilitates the adsorption of intermediates and the dissociation of H₂O. Moreover, the open 2D/3D structure formed by introducing the Co substrate further reduces the accumulation of heterogeneous nanosheets and promotes the radial diffusion of the electrolyte, significantly improving the utilization of active sites and shortening the electron transfer pathway. In addition, the superhydrophilic/superaerophobic interface achieved by constructing the hierarchical micro-nanostructure is beneficial to electrolyte infiltration and bubble desorption, thus ensuring favorable mass transfer. Therefore, Co(OH)₂-CeO₂/Co exhibits an excellent overall water-splitting activity in alkaline solution.

Phosphorus vacancy-engineered Ce-doped CoP nanosheets for the electrocatalytic oxidation of 5-hydroxymethylfurfural

The electrooxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furanedioic acid (FDCA) has received increasing attention. To achieve satisfactory electrooxidation of HMF, the development of an efficient electrocatalyst is particularly critical. Herein, porous Ce-CoP nanosheets integrating Ce doping and P vacancies are designed through a deep eutectic solvent approach, and they allow the excellent electrocatalytic oxidation of HMF to FDCA in 1 M KOH electrolyte with 100% HMF conversion, 98% FDCA yield, and a faradaic efficiency of 96.4% at low potential.

Efficient nitric oxide electroreduction toward ambient ammonia synthesis catalyzed by a CoP nanoarray

The ever-increasing anthropic NO emission from fossil fuel combustion has resulted in a series of severe environmental issues. Ambient electrocatalytic NO reduction has emerged as a promising route for sustainable...