Chao Xie

Nanoparticle-Stacked Porous Nickel–Iron Nitride Nanosheet: A Highly Efficient Bifunctional Electrocatalyst for Overall Water Splitting

Nanoparticle-stacked porous Ni3FeN nanosheets were synthesized through a simple nitridation reaction of the corresponding LDHs. The nanosheet is composed of stacked nanoparticles with more active sites exposed for electrocatalytic reactions. Thus, it exhibited excellent oxygen evolution reaction performance having an extremely low overpotential of 223 mV at 10 mA/cm(2) and hydrogen evolution reaction property with a very low overpotential of 45 mV at 10 mA/cm(2). This electrocatalyst as bifunctional electrodes is used to overall water splitting in alkaline media, showing a high performance with 10 mA/cm(2) at a cell voltage of 1.495 V.

Porous cobalt–iron nitride nanowires as excellent bifunctional electrocatalysts for overall water splitting

Designing highly active, earth-abundant and stable bifunctional electrocatalysts for both the oxygen (OER) and hydrogen (HER) evolution reactions is very crucial to overall water splitting. Herein, we developed nanoparticle-stacked porous Co3FeNx (NSP-Co3FeNx) nanowires as bifunctional electrocatalysts, exhibiting excellent OER and HER activity with a low overpotential of 222 mV at 20 mA cm-2 and 23 mV at 10 mA cm-2, respectively, due to their unique structural advantages with grain boundaries, defects and dislocations. Moreover, the electrocatalysts as bifunctional electrodes show a high performance with 10 mA cm-2 at a cell voltage of 1.539 V.

In situ confined synthesis of molybdenum oxide decorated nickel–iron alloy nanosheets from MoO42− intercalated layered double hydroxides for the oxygen evolution reaction

This work reports molybdenum oxide decorated NiFe alloy nanosheets with high OER activity by reducing MoO42− intercalated nickel–iron layered double hydroxides (LDHs). The presence of MoO42− successfully led to structural integrity, increase of active sites, and modification of the surface electronic properties of the NiFe alloy.

Controllable Synthesis of CoS2@N/S-Codoped Porous Carbon Derived from ZIF-67 for as a Highly Efficient Catalyst for the Hydrogen Evolution Reaction

A convenient, controllable method to fabricate an electrode is necessary to achieve the practical application of a hydrogen evolution reaction (HER) catalyst. In this work, an electrodeposition–ZIF conversion–sulfuration strategy is developed to produce a CoS2@N/S‐codoped porous carbon (CoS2@NSC/CFP) to drive the HER efficiently. CoS2@NSC/CFP was prepared by the electrodeposition of Co(OH)2 on a carbon fiber paper followed by conversion into ZIF‐67 and subsequent sulfuration with sulfur. The loading of electroactive components can be controlled easily in the range of 0.7–10.0 mg cm−2 by varying electrodeposition time from 5 min to 2 h. The resulting material can be employed directly as a working electrode for the HER and it shows an excellent catalytic activity and stability with an overpotential of 95 mV at 10 mA cm−2 and 158 mV to reach 100 mA cm−2 in an acidic medium. The high efficiency is related intimately to the high dispersion of ultra‐small CoS2 nanoparticles, heteroatom‐codoping, and the 3 D porous network configuration of the carbon fiber paper.

Engineering the coordination geometry of metal–organic complex electrocatalysts for highly enhanced oxygen evolution reaction

Designing highly efficient oxygen evolution reaction (OER) electrocatalysts is very important for various electrochemical devices. In this work, for the first time, we have successfully generated coordinatively unsaturated metal sites (CUMSs) in phytic acid–Co2+ (Phy–Co2+) based metal–organic complexes by engineering the coordination geometry with room-temperature plasma technology. The CUMSs can serve as active centers to catalyze the OER. The electron spin resonance and X-ray absorption spectra provide direct evidence that the coordination geometry is obviously modified with many CUMSs by the plasma treatment. The plasma treated Phy–Co2+ (P-Phy–Co2+) only requires an overpotential of 306 mV to reach 10 mA cm−2 on glassy carbon electrodes. When we expand this strategy to a CoFe bimetallic system, it only needs an overpotential of 265 mV to achieve 10 mA cm−2 with a small Tafel slope of 36.51 mV dec−1. P-Phy–Co2+ is superior to the state-of-the-art. Our findings not only provide alternative excellent OER electrocatalysts, but also introduce a promising principle to design advanced electrocatalysts by creating more CUMSs.

Rapidly engineering the electronic properties and morphological structure of NiSe nanowires for the oxygen evolution reaction

The oxygen evolution reaction (OER) is one of the most important reactions in a wide range of renewable energy technologies. It is important to develop highly efficient electrocatalysts for the OER due to its sluggish kinetics. The electronic properties and morphological structure of electrocatalysts can significantly affect their OER performance. Electrocatalysts with the morphology of nanosheets can expose more active sites which would enhance the OER activity. Here, we report an extremely simple and fast method to synthesize a NixFe1−xSe@Ni(Fe)OOH core–shell nanostructure with a nanosheet shell by a facile solvothermal selenization and ion exchange reaction. The NixFe1−xSe@Ni(Fe)OOH core–shell nanostructure gives an excellent catalytic activity toward the OER with an overpotential as low as 260 mV to reach a current density of 100 mA cm−2 and excellent electrochemical long-term stability in 1 M KOH solution. The enhanced OER activity can be attributed to the dual modulation of electronic properties and the morphological structure by Fe doping.

N, P-dual doped carbon with trace Co and rich edge sites as highly efficient electrocatalyst for oxygen reduction reaction

Oxygen reduction reaction (ORR) is key to fuel cells and metal-air batteries which are considered as the alternative clean energy. Various carbon materials have been widely researched as ORR electrocatalysts. It has been accepted that heteroatom doping and exposure of the edge sites can effectively improve the activity of carbon materials. In this work, we used a simple method to prepare a novel N, P-dual doped carbon-based catalyst with many holes on the surface. In addition, trace level Co doping in the carbon material forming Co–N–C active species can further enhance the ORR performance. On one hand, the doping can adjust the electronic structure of carbon atoms, which would induce more active sites for ORR. And on the other hand, the holes formed on the surface of carbon nanosheets would expose more edge sites and can improve the intrinsic activity of carbon. Due to the heteroatom doping and the exposed edge sites, the prepared carbon materials showed highly excellent ORR performance, close to that of commercial Pt/C.摘要本文使用有机分子配位聚合作用一步聚合、 碳化、 酸洗得到了一种N,P双掺杂碳材料. 其具有痕量掺杂的金属钴、 且具有更多活性边缘. X射线光电子能谱显示杂原子成功进入碳材料当中, 并且发现酸洗后钴的信号非常低, 证明酸洗后, 材料表面形成非常多的孔, 暴露出更多的边缘催化位点. 制备的碳材料具有大量催化活性位点, 因此表现出极其优异的电催化氧还原性能. 另外, 与Pt/C相比, 制备的多孔碳材料还具有较好的抗毒性与稳定性, 进一步显示了其在新能源电池领域的应用前景.

Defect-Enhanced Charge Separation and Transfer within Protection Layer/Semiconductor Structure of Photoanodes

Silicon (Si) requires a protection layer to maintain stable and long-time photoanodic reaction. However, poor charge separation and transfer are key constraint factors in protection layer/Si photoanodes that reduce their water-splitting efficiency. Here, a simultaneous enhancement of charge separation and transfer in Nb-doped NiOx /Ni/black-Si photoanodes induced by plasma treatment is reported. The optimized photoanodes yield the highest charge-separation efficiency (ηsep ) of ≈81% at 1.23 V versus reversible hydrogen electrode, corresponding to the photocurrent density of ≈29.1 mA cm-2 . On the basis of detailed characterizations, the concentration and species of oxygen defects in the NiOx -based layer are adjusted by synergistic effect of Nb doping and plasma treatment, which are the dominating factors for forming suitable band structure and providing a favorable hole-migration channel. This work elucidates the important role of oxygen defects on charge separation and transfer in the protection layer/Si-based photoelectrochemical systems and is encouraging for application of this synergistic strategy to other candidate photoanodes.

Crystalline TiO 2 protective layer with graded oxygen defects for efficient and stable silicon-based photocathode

The trade-offs between photoelectrode efficiency and stability significantly hinder the practical application of silicon-based photoelectrochemical devices. Here, we report a facile approach to decouple the trade-offs of silicon-based photocathodes by employing crystalline TiO2 with graded oxygen defects as protection layer. The crystalline protection layer provides high-density structure and enhances stability, and at the same time oxygen defects allow the carrier transport with low resistance as required for high efficiency. The silicon-based photocathode with black TiO2 shows a limiting current density of ~35.3 mA cm−2 and durability of over 100 h at 10 mA cm−2 in 1.0 M NaOH electrolyte, while none of photoelectrochemical behavior is observed in crystalline TiO2 protection layer. These findings have significant suggestions for further development of silicon-based, III–V compounds and other photoelectrodes and offer the possibility for achieving highly efficient and durable photoelectrochemical devices.While silicon-based materials can convert sunlight directly to fuel and electricity, balancing their stability and efficiency constrains usage. Here, authors protect silicon photocathodes with crystalline titanium dioxide layers with graded oxygen defects to improve both durability and efficiency.

Crystalline‐Water/Coordination Induced Formation of 3D Highly Porous Heteroatom‐Doped Ultrathin Carbon Nanosheet Networks for Oxygen Reduction Reaction

Development of highly efficient electrocatalysts with low cost for oxygen reduction reaction (ORR) is crucial for their application in fuel cells and metal‐air batteries. In this work, we report a synthesis of 3D heteroatom‐doped ultrathin carbon nanosheet networks directly starting from solid raw materials. This method represents an operationally simple, general, and sustainable strategy to various ultrathin carbon nanosheet networks. Evaporation of crystalline water and coordination interaction are proposed to be responsible for the formation of the 3D carbon nanosheet networks. The carbon nanosheet networks possess high surface area with micro‐ and macropores, large pore volume, ultrathin nanosheet structure, and effective N/S‐co‐doping. The as‐prepared materials show outstanding electrocatalytic ORR performance with more positive onset potential and half‐wave potential, good methanol tolerance, and excellent stability, compared with those of the porous carbons derived from the ZIF counterpart and commercial Pt/C. This work not only provides highly active ORR electrocatalysts via an operationally simple and green process and also demonstrates a general method to prepare 3D ultrathin carbon nanosheet networks without any additional template and solvent.