Efficient Electrocatalysts For Overall Water Splitting Research Articles

Bimetallic–organic frameworks derived heterointerface arrangements of V, N co-doped Co/Fe–selenide nanosheets electrocatalyst for efficient overall water-splitting

Due to their high specific surface area, modifiable chemical functionality, and accessibility of bountiful active sites, the metal–organic framework derivatives hold great potential for catalytic activity. Herein, heterointerface vanadium and nitrogen co-doped Co/Fe selenides inlaid in N-doped carbon shell are grown on nickel foam (V,N–Co/Fe–Se/C@NF) derived from V-doped bimetallic–organic frameworks (V–CoFe–MOF@NF), followed by chemical vapor deposition (CVD) selenization. The results show that V,N–Co/Fe–Se/C@NF requires lower overpotentials (η) for HER (η10 = 67 mV, η100 = 160 mV), and OER (η20 = 257 mV, η100 = 301 mV). Notably, the electrolyzer V,N–Co/Fe–Se/C@NF (+, −) needs 1.51 V cell voltage at 10 mA cm−2, lower than that of RuO2@NF (+)//Pt–C@NF (−) (1.59 V) to drive same current density. Thus, our work provides a new avenue for synthesis of MOF-derived heterointerfaces for clean hydrogen production at massive scale through water electrolysis.

Controllable disorder engineering in Mn-doped Co3O4/NF electrocatalyst for efficient overall water-splitting

The design of high-effective bifunctional non-noble electrocatalysts is a feasible strategy for water electrolysis. Non-noble metal oxide Co3O4/NF is a promising electrocatalyst. However, the wide application has been limited by its poor intrinsic activity for HER. In this work, controllable disorder engineering in Co3O4 was realized by a simple Mn-doping process. As higher disorder degree, a more and more Mn2+ and Co2+-rich surfaces of Co3O4/NF can be obtained, resulting in a faster charge transfer rate and more accessible active sites because of regulating the electronic structure and forming more defects. The optimized Co3O4/NF (Mn0.8Co2.2O4/NF) shows the enhanced HER and OER activity with an overpotential as low as 154 mV and 231 mV at 10 mA·cm−2, and only needs a cell voltage of 1.56 V for overall water-splitting. In a word, high-effective bifunctional non-noble electrocatalysts have been developed by controllable disorder engineering in Mn-doped Co3O4/NF.

Cu2Se nanowires shelled with NiFe layered double hydroxide nanosheets for overall water-splitting

It is imperative but challenging to develop non-noble metal-based bifunctional electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Our work reports a core–shell nanostructure that is constructed by the electrodeposition of ultrathin NiFe-LDH nanosheets (NiFe-LDHNS) on Cu2Se nanowires, which are obtained by selenizing Cu(OH)2 nanowires in situ grown on Cu foam. The obtained Cu2Se@NiFe-LDHNS electrocatalyst provides more exposed edges and catalytic active sites, thus exhibiting excellent OER and HER electrocatalytic performance in alkaline electrolytes. This catalyst needs only an overpotential of 197 mV for OER at 50 mA cm−2 and 195 mV for HER at 10 mA cm−2. Besides, when employed as a bifunctional catalyst for overall water-splitting, it requires a cell voltage of 1.67 V to reach 10 mA cm−2 in alkaline media. Furthermore, the corresponding water electrolyzer demonstrates robust durability for at least 40 h. The excellent performance of Cu2Se@NiFe-LDHNS might be ascribed to the synergistic effect from the ultrathin NiFe-LDHNS, the Cu2Se nanowires anchored on the Cu foam, and the formed core–shell nanostructure, which offers large surface area, ample active sites, and sufficient channels for gas and electrolyte diffusion. This work provides an efficient strategy for the fabrication of self-supported electrocatalysts for efficient overall water-splitting.

3D urchin like V-doped CoP in situ grown on nickel foam as bifunctional electrocatalyst for efficient overall water-splitting

Cobalt phosphide (CoP) is considered to be a potential candidate in the field of electrocatalysis due to its low-cost, abundant resources and high electrochemical stability. However, there is a great space for further improvement of its electrocatalytic performance since its charge transfer rate and catalytic activity have not reached a satisfactory level. Herein, we design and fabricate a three dimensional urchins like V-doped CoP with different amounts of V-doping on nickel foam electrode. The V-doped CoP/NF electrode with optimized amounts of V-doping (10%) exhibits outstanding hydrogen evolution reaction (HER) performance under universal-pH conditions and preeminent oxygen evolution reaction (OER) performance in alkaline media. Notably, the assembled water-splitting cell displays a cell voltage of only 1.53 V at 10 mA·cm−2 and has excellent durability, much better than many reported related bifunctional catalysts. The experiment results and theoretical analysis revealed that vanadium atoms replace cobalt atoms in CoP lattice. Vanadium doping can not only raise the density of electronic states near the Fermi level enhancing the conductivity of the catalyst, but can also optimize the free energy of hydrogen and oxygen-containing intermediates adsorption over CoP, thus promoting its catalytic activity. Moreover, the unique nanostructure of the catalyst provides the various shortened channels for charge transfer and reactant/electrolyte diffusion, which accelerates the electrocatalytic process. Also, the in situ growth strategy can improve the conductivity and stability of the catalyst.

In-situ formed N doped bamboo-like carbon nanotube decorated with Fe–Ni–Cr nanoparticles as efficient electrocatalysts for overall water-splitting

It is of tremendous significance to develop effective bifunctional electrocatalysts for electrochemical water-splitting to generate sustainable hydrogen energy. Herein, a facile and scalable strategy is evolved to design N doped bamboo-like carbon nanotube decorated with tri-metal nanoparticles (Fe–Ni–Cr/NC) for overall water-splitting in alkaline electrolyte. Coupling effects between different metals and intimately contact with the carbon matrix endow the obtained nanomaterial possesses splendid catalytic activity and stability for cathodic HER, anodic OER and overall water-splitting in alkaline electrolyte. The obtained Fe–Ni–Cr/NC exhibits the best catalytic performance for HER (284 mV@10 mA cm−2) relative to Fe–Cr/NC (368 mV), Ni–Cr/NC (314 mV) and Fe–Ni/NC (324 mV). For OER, a small overpotential of 210 mV is needed to drive 10 mAcm−2 which is superior to IrO2 (330 mV). Thus, the interactions between different metals act as paramount effects on promoting the catalytic activities. Benefiting from the outstanding catalytic performances for both HER and OER, the designed Fe–Ni–Cr/NC possesses splendid catalytic activity for overall water-splitting with a small potential of 1.64 V to deliver 10 mA cm−2. Moreover, the obtained nanomaterial also owns remarkable long-term stability in the measured electrolyte.

Surface modification of NiCo2Te4 nanoclusters: a highly efficient electrocatalyst for overall water-splitting in neutral solution

In this paper, we for the first time report the catalytic activity and durability of nickel cobaltite telluride (NiCo2Te4) nanocluster bifunctional catalysts can be significantly boosted by surface modification with perylene-tetracarboxylic-dianhydride for overall water-splitting in neutral solution. We reveal that tuning energy distribution of nanoclusters via a simple surface ligand can drastically increase the catalytic activity towards efficient hydrogen and oxygen evolution reaction simultaneously. A two-electrode based water electrolysis cell using this newly developed nanocluster catalyst operates at a low bias voltage of 1.55 V to achieve a current density of 10 mA·cm−2 in near-neutral pH solution for overall water-splitting. This, to the best of our knowledge, represents the most efficient mixed-transition-metal-based electrode that has so far been reported for electrochemical water splitting.