Single-atom Mo-tailored high-entropy-alloy ultrathin nanosheets with intrinsic tensile strain enhance electrocatalysis.

The precise structural integration of single-atom and high-entropy-alloy features for energy electrocatalysis is highly appealing for energy conversion, yet remains a grand challenge. Herein, we report a class of single-atom Mo-tailored PdPtNiCuZn high-entropy-alloy nanosheets with dilute Pt-Pt ensembles and intrinsic tensile strain (Mo1-PdPtNiCuZn) as efficient electrocatalysts for enhancing the methanol oxidation reaction catalysis. The as-made Mo1-PdPtNiCuZn delivers an extraordinary mass activity of 24.55 A mgPt-1 and 11.62 A mgPd+Pt-1, along with impressive long-term durability. The planted oxophilic Mo single atoms as promoters modify the electronic structure of isolated Pt sites in the high-entropy-alloy host, suppressing the formation of CO adsorbates and steering the reaction towards the formate pathway. Meanwhile, Mo promoters and tensile strain synergistically optimize the adsorption behaviour of intermediates to achieve a more energetically favourable pathway and minimize the methanol oxidation reaction barrier. This work advances the design of atomically precise catalytic sites by creating a new paradigm of single atom-tailored high-entropy alloys, opening an encouraging pathway to the design of CO-tolerance electrocatalysts.

Improved Plasmonic Hot-Electron Capture in Au Nanoparticle/Polymeric Carbon Nitride by Pt Single Atoms for Broad-Spectrum Photocatalytic H2 Evolution.

Rationally designing broad-spectrum photocatalysts to harvest whole visible-light region photons and enhance solar energy conversion is a "holy grail" for researchers, but is still a challenging issue. Herein, based on the common polymeric carbon nitride (PCN), a hybrid co-catalysts system comprising plasmonic Au nanoparticles (NPs) and atomically dispersed Pt single atoms (PtSAs) with different functions was constructed to address this challenge. For the dual co-catalysts decorated PCN (PtSAs-Au2.5/PCN), the PCN is photoexcited to generate electrons under UV and short-wavelength visible light, and the synergetic Au NPs and PtSAs not only accelerate charge separation and transfer though Schottky junctions and metal-support bond but also act as the co-catalysts for H2 evolution. Furthermore, the Au NPs absorb long-wavelength visible light owing to its localized surface plasmon resonance, and the adjacent PtSAs trap the plasmonic hot-electrons for H2 evolution via direct electron transfer effect. Consequently, the PtSAs-Au2.5/PCN exhibits excellent broad-spectrum photocatalytic H2 evolution activity with the H2 evolution rate of 8.8 mmol g-1 h-1 at 420 nm and 264 µmol g-1 h-1 at 550 nm, much higher than that of Au2.5/PCN and PtSAs-PCN, respectively. This work provides a new strategy to design broad-spectrum photocatalysts for energy conversion reaction.

MnIn2S4 nanosheets growing on rods-like ß-MnO2 via covalent bonds as high-performance photocatalyst for boosting Cr(VI) photocatalytic reduction under visible light irradiation: Behavior and mechanism study.

It is an urgent and onerous task to develop catalysts for photocatalytic reduction of Cr(VI) in wastewater under wide pH range. In this work, a novel hierarchical Z-scheme MnO2/MnIn2S4 (MISO) heterojunction photocatalyst with MnIn2S4 nanosheets growing on the surface of ß-MnO2 nanorods is constructed for efficient photocatalytic reduction of Cr(VI). The optimized 2.0-MISO photocatalyst exhibits the almost 100% reduction efficiency in the pH range of 2.1-5.6 under visible light irradiation, and the apparent rate constant is 0.05814 min-1, which is 29.96 and 3.27 times higher than the pure ß-MnO2 and MnIn2S4, respectively. A efficient photocatalytic reduction of Cr(VI) to Cr(III) species on 2.0-MISO photocatalyst in actual industry wastewater (286.7 mg/L) up to 99.8% is achieved. Under natural light, the 2.0-MISO photocatalyst also shows rapid reduction of Cr(VI) species. The photocorrosion of MnIn2S4 was significantly hindered by the construction of heterojunction. And the O2- and e- species are the main active species during the Cr(VI) photoreduction process. The connection mode between MnIn2S4 and ß-MnO2 is verified by DFT calculations and a possible photocatalytic mechanism is also proposed.

Short-Range Diffusion Enables General Synthesis of Medium-Entropy Alloy Aerogels.

Medium-entropy alloy aerogels (MEAAs) with the advantages of both multimetallic alloys and aerogels are promising new materials in catalytic applications. However, limited by the immiscible behavior of different metals, achieving single-phase MEAAs is still a grand challenge. Herein, a general strategy for preparing ultralight 3D porous MEAAs with the lowest density of 39.3 mg cm-3 among the metal materials is reported, through combining auto-combustion and subsequent low-temperature reduction procedures. The homogenous mixing of precursors at the ionic level makes the short-range diffusion of metal atoms possible to drive the formation of single-phase MEAAs. As a proof of concept in catalysis, as-synthesized Ni50 Co15 Fe30 Cu5 MEAAs exhibit a high mass activity of 1.62 A mg-1 and specific activity of 132.24 mA cm-2 toward methanol oxidation reactions, much higher than those of the low-entropy counterparts. In situ Fourier transform infrared and NMR spectroscopies reveal that MEAAs can enable highly selective conversion of methanol to formate. Most importantly, a methanol-oxidation-assisted MEAAs-based water electrolyzer can achieve a low cell voltage of 1.476 V at 10 mA cm-2 for making value-added formate at the anode and H2 at the cathode, 173 mV lower than that of traditional alkaline water electrolyzers.

Mesoporous cobalt ferrite phosphides/reduced graphene oxide as highly effective electrocatalyst for overall water splitting.

Although the electrochemical production of hydrogen has been considered as a promising strategy to obtain the sustainable resources, the sluggish kinetics of anodic oxygen evolution reaction (OER) hindered the sustainable energy development. Herein, we design mesoporous cobalt ferrite phosphides hybridized on reduced graphene oxide (rGO) as a highly efficient bifunctional catalyst through a simple nanocasting method. The hybrid catalyst possesses the abundant interface, which provides the large active sites, as well as the hybrid rGO accelerates the electron exchange and ion diffusion. Moreover, the mesoporous structure not only prevents the aggregation of actives sites, but also benefits for the rapid escape of bubbles during catalytical process, which can significantly improve the catalytic performance. Consequently, the resulting mCo0.5Fe0.5P/rGO shows superior catalytic performance with a low overpotential of 250 mV at a current density of 10 mA cm-2 for OER and outstanding long-term stability. More importantly, an electrolyzer with mCo0.5Fe0.5P/rGO as both anode and cathode catalysts shows a low voltage of 1.66 V to afford a current density of 10 mA cm-2. This work offers a new route for designing the highly efficient OER and overall water splitting electrocatalysts.

High-Index Faceted PdPtCu Ultrathin Nanorings Enable Highly Active and Stable Oxygen Reduction Electrocatalysis.

Ultrathin nanosheet catalysts deliver great potential in catalyzing the oxygen reduction reaction (ORR), but encounter the ceiling of the surface atomic utilizations, thus presenting a challenge associated with further boosting catalytic activity. Herein, a kind of PdPtCu ultrathin nanorings with increased numbers of electrocatalytically active sites is reported, with the purpose of breaking the activity ceiling of conventional catalysts. The as-made PdPtCu nanorings possess abundant high-index facets at the edge of both the exterior and interior surfaces. An ultrahigh electrochemical active surface area of 92.2 m2 g-1 PGM is achieved on this novel catalyst, much higher than that of the commercial Pt/C catalyst. The optimized Pd39 Pt33 Cu28 /C shows a great enhanced ORR activity with a specific activity of 2.39 mA cm-2 and a mass activity of 1.97 A mg-1 PGM at 0.9 V (versus RHE), as well as superior durability within 30 000 cycles. Density function theory calculations reveal that the high-index facets and alloying Cu atoms can optimize the oxygen adsorption energy, explaining the enhanced ORR activity. Overcoming a key technical barrier in sub-nanometer electrocatalysts, this work successfully introduces the hollow structures into the ultrathin nanosheets, heralding the exciting prospects of high-performance ORR catalysts in fuel cells.

Industrially promising NiCoP nanorod arrays tailored with trace W and Mo atoms for boosting large-current-density overall water splitting.

Nanoarray catalysts supported on substrates provide an opportunity for industrially promising overall water splitting at large current densities. However, most of the present electrocatalysts show high overpotentials at a large current density, inducing a low efficiency for industrial water electrolysis. Herein, using the classic NiCoP nanorod arrays as the basic catalyst model, we presented a trace W and Mo co-doped strategy to boost the overall water splitting electrocatalysis at an industrial current density. After a trace amount of W and Mo atoms was doped, the constructed W and Mo co-doped NiCoP nanorod arrays (W,Mo-NiCoP/NF) show a low overpotential of 249 mV towards the hydrogen evolution reaction (HER) at a very large current density of 1000 mA cm-2. We deduce that the regulation of the electronic structure caused by the trace W and Mo atoms, as well as the intrinsic features of nanoarrays leads to enhanced catalytic activity. In addition, a significant enhancement towards the oxygen evolution reaction (OER) was also achieved by this co-doped strategy. Finally, an overall water splitting device using W,Mo-NiCoP/NF as both the anode and cathode was assembled to exhibit a low cell voltage of 1.85 V at a large current density of 500 mA cm-2 and an excellent long-term stability within 50 h, better than most of the state-of-the-art bifunctional electrocatalysts yet reported. Our results highlight the significance of trace-doping engineering in industrial water electrolysis.