A highly efficient Fe-doped Ni3S2 electrocatalyst for overall water splitting

The development of efficient and stable electrocatalysts with earth-abundant elements for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in the same electrolyte is incontrovertibly vital in water electrolysis. However, their large-scale fabrication remains a great challenge. Here, we report a self-supported electrocatalyst in the form of Fe-doped Ni₃S₂ nanoparticles in-situ grown on three-dimensional (3D) conductive Fe−Ni alloy foam (Fe−Ni₃S₂/AF) by surface-assisted chemical vapor transport (SACVT) method. Homogeneous growth environment and scalability of SACVT method allow Fe−Ni₃S₂ nanoparticles uniformly growing on AF in large-scale. Fe−Ni₃S₂/AF exhibits high activity and durability when act as HER catalyst and OER precatalyst in alkaline media. The HER and OER overpotential at 10 mA/cm² is considerably small, only 75 and 267 mV, respectively. Moreover, the electrolyzer assembled by Fe−Ni₃S₂/AF for overall water splitting exhibits a low cell voltage and high durability in long-term test. Based on experiments and theoretical calculation, the significantly enhanced activity could be originated from the incorporation of Fe, which contributed to increase the electrochemical active surface area, enhance electrical conductivity, optimize the hydrogen and H₂O adsorption energy of Ni₃S₂ (101) surface in HER, and form active bimetallic Ni−Fe(oxy)hydroxide in OER. The excellent durability of self-supported Fe−Ni₃S₂/AF could be benefited from the in-situ growth of Fe−Ni₃S₂ nanoparticles on 3D AF, which could ensure closely mechanical adhesion between active materials and substrate, promote charge transport and increase surface area. This work provides a facile method for large-scale synthesis of electrocatalysts with high activity and long-term durability for efficient water electrolysis in alkaline media.

     

Self-supporting amorphous nanoporous NiFeCoP electrocatalyst for efficient overall water splitting

The design of cost-effective and earth-abundant bifunctional electrocatalysts for highly efficient oxy-gen evolution reaction(OER)and hydrogen evolution reaction(HER)is important for water splitting as an advanced renewable energy transformation system.In this work,the self-supporting amorphous NiFeCoP catalyst with nanoporous structure via a facile electrochemical dealloying method is reported.Benefiting from the bicontinuous nanostructure,disordered atomic arrangement,abundant active sites and synergic effect of various transition metals,the as-prepared nanoporous NiFeCoP(np-NiFeCoP)cat-alyst exhibits good electrocatalytic activity,which achieves the current densities of 10 mA cm-2 at low overpotentials of 244 mV and 105 mV for OER and HER in 1.0 M KOH,respectively.In addition,the bifunc-tional electrocatalyst also shows outstanding and durable electrocatalytic activity in water splitting with a small voltage of 1.62 V to drive a current density of 10 mA cm-2 in a two-electrode electrolyzer system.The present work would provide a feasible strategy to explore the efficient and low-cost bifunctional electrocatalysts toward overall water splitting.     

A bifunctional electrocatalyst of PtNi nanoparticles immobilized on three-dimensional carbon nanofiber mats for efficient and stable water splitting in both acid and basic media

Inspired by the excellent activity of platinum in hydrogen evolution reaction (HER) and the good performance of Ni-based compounds in oxygen evolution reaction (OER), a bifunctional electrocatalyst PtNi carbon nanofiber (CNF) is designed and fabricated using electrospinning followed by carbonization. Ultra-small PtNi nanoparticles of several nanometers in size are densely dispersed on every CNF, along with a few larger nanoparticles with sizes of several decades of nanometers. The as-prepared catalysts can be directly used as an electrode and act as high-efficiency materials for water splitting, including HER and OER. For HER activity, the PtNi/CNFs reach 10 mA cm^?2 current density at low overpotentials of 34 mV and exhibit a small Tafel slope of 31 mV dec^?1 in acidic electrolytes of 0.5 M H₂SO₄, which is close to that of commercial Pt/C (20 wt%) electrocatalytic catalysts. In 1 M KOH solution, the PtNi/CNFs also exhibit excellent HER activity with a low overpotential of 82 mV to achieve a current density of 10 mA cm^?2 and a small Tafel slope of 34 mV dec^?1. Moreover, the PtNi/CNFs also show good activity for OER in alkaline electrolyte of 1 M KOH with a Tafel slope of 159 mV dec^?1 and a small overpotential of 151 mV to reach a current density of 10 mA cm^?2. In addition, the OER performance of the PtNi/CNFs in acid media is also favorable, with a 198 mV dec^?1 Tafel slope. The decent activity of the PtNi/CNFs for water splitting originates from the synergistic effects of using Pt and Ni, large amounts of ultra-small nanoparticles densely dispersed on the CNFs, high conductivity of the support materials and interconnected three-dimensional structures of the carbon nanofiber mats.     

A co-coordination strategy to realize janus-type bimetallic phosphide as highly efficient and durable bifunctional catalyst for water splitting

In this work,a Janus-type dual-ligand metal-organic frameworks derived bimetallic (Fe,Co)P nanoparticles embedded carbon nanotube (CNT) skeleton (DLD-FeCoP@CNT) is presented and synthesized via a facile co-coordination synthesis strategy.The DLD-FeCoP@CNT hybrid shows much better performances for OER and HER with much lower Tafel slope of 39.6 (57.1) mV dec-1,an overpotential of 286 (166) mV@10 mA cm-2 and better stability for OER (HER) in 1 M KOH.Being both cathode and anode for water splitting,it requires only a low voltage of 1.67 V to obtain 10 mAcm-2 with nearly 100％ faradaic efficiency,which is close to Pt/C//RuO2 cell.Density functional theory calculations based on the bimetallic phosphide (Fe0.3Co0.7P) model reveal that,compared with the monometallic FeP or CoP,the enhanced catalytic activities of Fe0.3Co0.7P is mainly manifested in its free energy of H adsorption (△GH*) closer to zero,larger binding strength for H2O and higher electrical conductivity.     

Porous Pt nanoframes decorated with Bi(OH)3 as highly efficient and stable electrocatalyst for ethanol oxidation reaction

Nano Research - High-quality Pt-based catalysts are highly desirable for ethanol oxidation reaction (EOR), which is of critical importance for the commercial applications of direct ethanol fuel...     

Ternary non-noble metal zinc-nickel-cobalt carbonate hydroxide cocatalysts toward highly efficient photoelectrochemical water splitting

TiO₂ photoanodes have aroused intensive research interest in photoelectrochemical (PEC) water splitting. However, they still suffer from poor electron-hole separation and sluggish oxygen evolution dynamics, leading to the low photoconversion efficiency and limiting commercial application. Here, we designed and fabricated novel ternary non-noble metal carbonate hydroxide (ZNC-CH) nanosheet cocatalysts and integrated them with TiO₂ nanorod arrays as highly efficient photoanodes of PEC cells. Compared with the pristine TiO₂, the photocurrent of photoanode with the optimal amount of ZNC-CH represents 3.2 times enhancement, and the onset potential is shifted toward the negative potential direction of 62 mV. The remarkable enhancement is attributed to the suppressed carrier recombination and enhanced charge transfer efficiency at the interface of TiO₂, ZNC-CH and electrolyte, which is closely related to the zinc elements modulated intrinsic activity of catalysts. Our results demonstrate that the introduction of multimetallic ZNC-CH cocatalysts onto photoanodes is a promising strategy to improve the PEC efficiency.     

Ni-NiO/N-C的制备及其电解水析氢性能

电催化分解水制氢(HER)被认为是最具应用前景的能量转换方式之一,可同时获得高纯度氢气并实现能量储存与转化,其关键在于低廉、高效且高稳定HER电催化剂的设计与开发.采用一步水热法得到羟基氧化镍/聚苯胺(NiOOH/PANI)催化剂前驱体,经800℃热解后制备出Ni-NiO/N-C负载型电催化剂,并考察其HER性能.采用...     

Heterogeneous lamellar-edged Fe-Ni(OH)2/Ni3S2 nanoarray for efficient and stable seawater oxidation

Development of efficient non-precious catalysts for seawater electrolysis is of great significance but challenging due to the sluggish kinetics of oxygen evolution reaction(OER)and the impairment of chlorine electrochemistry at anode.Herein,we report a heterostructure of Ni₃S₂nanoarray with secondary Fe-Ni(OH)₂lamellar edges that exposes abundant active sites towards seawater oxidation.The resultant Fe-Ni(OH)₂/Ni₃S₂nanoarray works directly as a free-standing anodic electrode in alkaline artificial seawater.It only requires an overpotential of 269 mV to afford a current density of 10 mA·cm^-2and the Tafel slope is as low as 46 m V·dec^-1.The 27-hour chronopotentiometry operated at high current density of 100 mA·cm^-2shows negligible deterioration,suggesting good stability of the Fe-Ni(OH)₂/Ni₃S₂@NF electrode.Faraday efficiency for oxygen evolution is up to?95%,revealing decent selectivity of the catalyst in saline water.Such desirable catalytic performance could be benefitted from the introduction of Fe activator and the heterostructure that offers massive active and selective sites.The density functional theory(DFT)calculations indicate that the OER has lower theoretical overpotential than Cl₂ evolution reaction in Fe sites,which is contrary to that of Ni sites.The experimental and theoretical study provides a strong support for the rational design of high-performance Fe-based electrodes for industrial seawater electrolysis.     

钴-镍双金属磷化物中空纳米笼用于高效电解水

制备一种低成本、高效、稳定耐用的双功能电催化剂对于电催化水分解至关重要.本文采用自模板策略和原位磷化工艺相结合的方法构建了一种具有中空结构的钴镍双金属磷化物纳米笼(CoNiP_(x)).由于其独特的中空结构和钴镍双金属之间的协同效应,合成的CoNiP_(x)中空纳米笼催化剂在全pH值范围的电解质中对析氢反应均表现出优异...     

Wet-chemistry synthesis of cobalt carbide nanoparticles as highly active and stable electrocatalyst for hydrogen evolution reaction

Transition metal carbide (TMC) nanomaterials are promising alternatives to Pt,and are widely used as heterogeneous electrocatalysts for the electrochemical hydrogen evolution reaction (HER).In this work,a bromide-induced wet-chemistry strategy to synthesize Co2C nanopartides (NPs) was developed.Such NPs exhibited high electrocatalytic activity (η =181 mV for j =-10 mA.cm-2) and long-term stability (no obvious performance decrease after 4,000 cycles) for the HER.This study will pave the way for the design and fabrication of TMC NPs via a wetchemistry method,and will have significant impacts on broader areas such as nanocatalysis and energy conversion.     

Facile one-pot synthesis of nanocoral-like cerium-activated cobalt selenide: a highly efficient electrocatalyst for oxygen evolution reaction

The development of hydrogen production via environment-friendly and efficient electrochemical water splitting technology leans heavily on the exploitation of highly active and durable oxygen evolution reaction (OER) electrocatalysts. Herein, nanocoral-like cerium-activated cobalt selenide (Ce-CoSe₂) nanocomposites to enhance the OER catalytic activity have been successfully prepared by one-pot hydrothermal route via simply altering the cerium content. Owing to the ingenious introduction of cerium, as-prepared Ce-CoSe₂ electrode displays remarkable OER performance in comparison with CoSe₂. The nanocoral-like Ce-CoSe₂ catalyst prepared under optimal condition just needs low overpotential of 276 and 398 mV at 10 and 50 mA cm^?2, respectively. Additionally, it attains the current density of 255 mA cm^?2 at the potential of 2.0 V vs. RHE, and shows long-term stability during OER. This work offers a simple and feasible pathway for the design and construct of metal dichalcogenides for green and renewable hydrogen production by electrocatalytic water splitting.

Graphical abstract

     

NixCo0.85-xSe中空纳米球的溶液化学法合成、双功能特性及锌空电池应用（英文）

合成高活性、低成本、双功能特性的电催化剂是目前发展新能源材料的重要任务.过渡金属硒化物具有较高的电导特性、可调节的物理化学特性等,成为了开发高效氧还原和氧析出催化剂的研究热点.本文采用多元醇溶液化学法合成了具有较大比表面积的NixCo0.85-xSe中空纳米球.该催化剂的ORR起始电位达到0.89 V,OER在10 mA cm^-2电流密度下的过电位达到305 mV.以NixCo0.85-xSe中空纳米球为空气电极、锌片为阴极组成的锌空电池具有良好的比容量和循环稳定性.NixCo0.85-xSe中空纳米球优异的催化性能主要归因于较大的比表面积、Ni和Co的协同催化特性以及良好的导电性.本文为设计高效的锌空电池催化剂提供了良好的理论基础和实验支持.     

One-step synthesis of N,P co-doped porous carbon electrocatalyst for highly efficient nitrogen fixation

Heteroatom-doped porous carbon has attracted many researchers'interests owing to their hierarchical porous and more active sites for nitrogen reduction reaction...     

In situ grown Fe3O4 particle on stainless steel:A highly efficient electrocatalyst for nitrate reduction to ammonia

NH3 is an essential feedstock for fertilizer synthesis.Industry-scale NH3 synthesis mostly relies on the Haber-Bosch method,however,which suffers from massive C...     

Organic-acid-assisted synthesis of a 3D lasagna-like Fe-N-doped CNTs-G framework: An efficient and stable electrocatalyst for oxygen reduction reactions

The scalable preparation of multi-functional three-dimensional (3D) carbon nanotubes and graphene (CNTs-G) hybrids via a well-controlled route is urgently required and challenging.Herein,an easily operated,oxalic acid-assisted method was developed for the in situ fabrication of a 3D lasagna-like Fe-N-doped CNTs-G framework (LMFC) from a precursor designed at the molecular level.The well-organized architecture of LMFC was constructed by multi-dimensionally interconnected graphene and CNTs which derived from porous graphene sheets,to form a fundamentally robust and hierarchical porous structure,as well as favorable conductive networks.The impressive oxygen reduction reaction (ORR) performances in both alkaline and acidic conditions helped confirm the significance of this technically favorable morphological structure.This product was also the subject of research for the exploration of decisive effects on the performance of ORR catalysts with reasonable control variables.The present work further advances the construction of novel 3D carbon architectures via practical and economic routes.