Jianwen Huang

Flexible cobalt phosphide network electrocatalyst for hydrogen evolution at all pH values

High-performance electrocatalysts for water splitting at all pH values have attracted considerable interest in the field of sustainable hydrogen evolution. Herein, we report an efficient electrocatalyst with a nanocrystalline cobalt phosphide (CoP) network for water splitting in the pH range of 0–14. The novel flexible electrocatalyst is derived from a desirable nanocrystalline CoP network grown on a conductive Hastelloy belt. This kind of self-supported CoP network is directly used as an electrocatalytic cathode for hydrogen evolution. The nanocrystalline network structure results in superior performance with a low onset overpotential of ~45 mV over a broad pH range of 0 to 14 and affords a catalytic current density of 100 mA·cm−2 even in neutral media. The CoP network exhibits excellent catalytic properties not only at extreme pH values (0 and 14) but also in neutral media (pH = 7), which is comparable to the behavior of state-of-the-art platinum-based metals. The system exhibits an excellent flexible property and maintains remarkable catalytic stability during continuous 100-h-long electrolysis even after 100 cycles of bending/extending from 100° to 250°.

Strongly Coupled Molybdenum Carbide on Carbon Sheets as a Bifunctional Electrocatalyst for Overall Water Splitting

High-performance and affordable electrocatalysts from earth-abundant elements are desirably pursued for water splitting involving hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Here, a bifunctional electrocatalyst of highly crystalline Mo2 C nanoparticles supported on carbon sheets (Mo2 C/CS) was designed toward overall water splitting. Owing to the highly active catalytic nature of Mo2 C nanoparticles, the high surface area of carbon sheets and efficient charge transfer in the strongly coupled composite, the designed catalysts show excellent bifunctional behavior with an onset potential of -60 mV for HER and an overpotential of 320 mV to achieve a current density of 10 mA cm-2 for OER in 1 m KOH while maintaining robust stability. Moreover, the electrolysis cell using the catalyst only requires a low cell voltage of 1.73 V to achieve a current density of 10 mA cm-2 and maintains the activity for more than 100 h when employing the Mo2 C/CS catalyst as both anode and cathode electrodes. Such high performance makes Mo2 C/CS a promising electrocatalyst for practical hydrogen production from water splitting.

A New Member of Electrocatalysts Based on Nickel Metaphosphate Nanocrystals for Efficient Water Oxidation

High-performance electrocatalysts are desired for electrochemical energy conversion, especially in the field of water splitting. Here, a new member of phosphate electrocatalysts, nickel metaphosphate (Ni2 P4 O12 ) nanocrystals, is reported, exhibiting low overpotential of 270 mV to generate the current density of 10 mA cm-2 and a superior catalytic durability of 100 h. It is worth noting that Ni2 P4 O12 electrocatalyst has remarkable oxygen evolution performance operating in basic media. Further experimental and theoretical analyses demonstrate that N dopant boosts the catalytic performance of Ni2 P4 O12 due to optimizing the surface electronic structure for better charge transfer and decreasing the adsorption energy for the oxygenic intermediates.

FeOx/FeP hybrid nanorods neutral hydrogen evolution electrocatalysis: insight into interface

The electrocatalytic interface plays a crucial role in driving the water splitting reaction. Herein, we report a rational constructed interface of Fe–O–P hybrid nanorods co-catalyst playing a significant role in high-performance hydrogen generation from neutral water. It is worth noting that the FeOx/FeP hybrid structure exhibits remarkably low overpotential of 96 mV at a current density of 10 mA cm−2 with a small Tafel slope of 47 mV dec−1 and maintains excellent electrolytic durability over 60 h, placing it at the forefront among the best hydrogen evolution electrocatalysts operating in neutral media. The increased Tafel value contributed by FeOx elimination demonstrates the important effect of the FeOx/FeP interface. Additionally, theoretical investigations reveal deeper insights into the FeOx/FeP interface: firstly, the FeOx facilitates the adsorption and dissociation of water molecules and accelerates the supply of hydrogen atoms in the Volmer–Heyrovsky reaction; secondly, the interface further optimizes the Gibbs free energy for hydrogen adsorption at the FeP surface.

Emission switching in carbon dots coated CdTe quantum dots driving by pH dependent hetero-interactions

Due to the different emission mechanism between fluorescent carbon dots and semiconductor quantum dots (QDs), it is of interest to explore the potential emission in hetero-structured carbon dots/semiconducting QDs. Herein, we design carbon dots coated CdTe QDs (CDQDs) and investigate their inherent emission. We demonstrate switchable emission for the hetero-interactions of the CDQDs. Optical analyses indicate electron transfer between the carbon dots and the CdTe QDs. A heterojunction electron process is proposed as the driving mechanism based on N atom protonation of the carbon dots. This work advances our understanding of the interaction mechanism of the heterostructured CDQDs and benefits the future development of optoelectronic nanodevices with new functionalities.

Sulfur‐Doped Rhenium Selenide Vertical Nanosheets: A High‐Performance Electrocatalyst for Hydrogen Evolution

Developing highly efficient electrocatalysts for hydrogen generation from water has been a crucial option for future energy conversion and storage. Rhenium dichalcogenides (ReX2, X=S or Se) have attracted tremendous research interests due to their unique distorted‐1T phase and anisotropic electronic structure. So far, there is no report about S doped ReSe2 electrocatalyst. In this work, we present a three‐dimensional nanosheets electrocatalyst derived from sulfur‐doped rhenium selenide (ReSe2(1–x)S2x) grown on carbon fiber paper (CFP) for water splitting. It is noting that the catalytic activity could be significantly fine‐tuned by controlling quantity of sulfur dopant. ReSe1.78S0.22/CFP cathode exhibits the best performance with a Tafel slope of 84 mV dec−1, an overpotential of 123 mV to drive the current density of 10 mA cm−2 as well as a long‐term stability of 30 h. The X‐ray photoelectron spectroscopy and density functional theory calculations confirm that sulfur‐doped structure, especially the dangling sulfur atoms adsorbed on the surface Se atom kars, achieves a more thermoneutral hydrogen adsorption energy, conducing an optimized catalytic activity of the basal plane. This study demonstrates that S doped ReSe2 could be a promising candidate electrocatalyst for hydrogen evolution.

High-Performance SERS Substrate Based on Hierarchical 3D Cu Nanocrystals with Efficient Morphology Control

Cu nanocrystals of various shapes are synthesized via a universal, eco-friendly, and facile colloidal method on Al substrates using hexadecylamine (HDA) as a capping agent and glucose as a reductant. By tuning the concentration of the capping agent, hierarchical 3D Cu nanocrystals show pronounced surface-enhanced Raman scattering (SERS) through the concentrated hot spots at the sharp tips and gaps due to the unique 3D structure and the resulting plasmonic couplings. Intriguingly, 3D sword-shaped Cu crystals have the highest enhancement factor (EF) because of their relatively uniform size distribution and alignment. This work opens new pathways for efficiently realizing morphology control for Cu nanocrystals as highly efficient SERS platforms.

Cytomembrane-Structure-Inspired Active Ni-N-O Interface for Enhanced Oxygen Evolution Reaction

Surface/interface design is one of the most significant and promising motivations to develop high-performance catalysts for electrolytic water splitting. Here, the nature of cytomembrane having the most effective and functional surface structure is mimicked to fabricate a new configuration of Ni-N-O porous interface nanoparticles (NiNO INPs) with strongly interacting nanointerface between the Ni3 N and NiO domains, for enhancing the electrocatalytic oxygen evolution reaction (OER) performance. The combination of transmission electron microscopy and electrochemical investigations, tracking the correlation between microstructure evolution and catalytic activity, demonstrate the strongly coupled nanointerface for an approximately sixfold improvement of electrolytic efficiency. Density functional theory simulates the electrocatalytic process with a maximum of 85% reduction of the energy barrier. Further investigations find that the real active site for the OER in the NiNO INPs is the strongly coupled Ni-N-O nanointerface, not the derived amorphous hydroxide, during the OER process. The determination of the correlation of constructed nanointerface with catalytic properties suggests a significant strategy toward the rational design of catalysts for efficient water electrocatalysis.