Recent Advances on Water-Splitting Electrocatalysis Mediated by Noble-Metal-Based Nanostructured Materials

Hydrogen produced via water electrolysis can act as an ideal clean chemical fuel with superb gravimetric energy density and high energy conversion efficiency, solving the problems of conventional fossil fuel exhaustion and environmental contamination. Transition metal sulfides (TMS) have been extensively explored as effective, widely available alternatives to precious metals in overall water splitting. Herein, recent advances, covering preparation methods, intrinsic electrocatalytic performance, and optimization strategies, relating to TMS-based bifunctional electrocatalysts have been summarized systematically and comprehensively. Firstly, a general introduction to the reaction mechanisms and key parameters of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is provided. Next, the physicochemical properties of TMS and typical synthesis methods are introduced to give guidance for fabricating TMS materials with well-defined structures, controllable compositions, and excellent performance. Importantly, the intrinsic activities of TMS-based electrocatalysts and several strategies for improving their bifunctional electrocatalytic performance during water electrolysis are discussed in detail. Finally, perspectives covering the challenges and opportunities related to the further development of TMS-based materials with high activity and long-term durability for overall water splitting are given. The aim herein is to provide guidelines for the design and fabrication of TMS-based bifunctional electrocatalysts with excellent performance and to accelerate their large-scale practical application in water electrolysis.

Recent advances in transition-metal-sulfide-based bifunctional electrocatalysts for overall water splitting

Herein, we highlighted that a catalyst system of NiSe2 nanoparticle/NiO nanosheet catalyst exhibited efficient synergism for energy and environmental-relevant urea-assisted water electrolysis reactions. The spectral study and microscopic analysis demonstrated the formation of NiSe2 nanoparticle/NiO nanosheet heterostructure and efficient Ni O bond and Ni Se bond synergism. Owing to various factors such as the strong synergetic coupling effects between NiSe2 nanoparticle and NiO nanosheet, unique structure features, increased active sites and amount of intrinsic Ni3+ ions, efficient synergism was found on the NiSe2 Nanoparticle/NiO nanosheet for urea-assisted water electrolysis by comparing with the NiSe2 Nanoparticle and NiO nanosheet alone. It required a cell voltage of 1.39 V, about 210 mV less than that of water electrolysis, confirming the less energy consumption during the electrolysis. Notably, it also shows remarkably superior long-term durability. The current work may extend the nanoparticle-nanosheet catalysts system for simultaneous wastewater treatment and clean energy production.

Efficient synergism of NiSe2 nanoparticle/NiO nanosheet for energy-relevant water and urea electrocatalysis

New insight into the effect of fluorine doping and oxygen vacancies on electrochemical performance of Co2MnO4 for flexible quasi-solid-state asymmetric supercapacitors

Transition metal hydroxides (M-OH) and their heterostructures (X|M-OH, where X can be a metal, metal oxide, metal chalcogenide, metal phosphide, etc.) have recently emerged as highly active electrocatalysts for hydrogen evolution reaction (HER) of alkaline water electrolysis. Lattice hydroxide anions in metal hydroxides are primarily responsible for observing such an enhanced HER activity in alkali that facilitate water dissociation and assist the first step, the hydrogen adsorption. Unfortunately, their poor electronic conductivity had been an issue of concern that significantly lowered its activity. Interesting advancements were made when heterostructured hydroxide materials with a metallic and or a semiconducting phase were found to overcome this pitfall. However, in the midst of recently evolving metal chalcogenide and phosphide based HER catalysts, significant developments made in the field of metal hydroxides and their heterostructures catalysed alkaline HER and their superiority have unfortunately been given negligible attention. This review, unlike others, begins with the question of why alkaline HER is difficult and will take the reader through evaluation perspectives, trends in metals hydroxides and their heterostructures catalysed HER, an understanding of how alkaline HER works on different interfaces, what must be the research directions of this field in near future, and eventually summarizes why metal hydroxides and their heterostructures are inevitable for energy-efficient alkaline HER.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/anie.202015738

Strategies and Perspectives to Catch the Missing Pieces in Energy-Efficient Hydrogen Evolution Reaction in Alkaline Media

Efficient catalysis of N doped NiS/NiS2 heterogeneous structure

Water splitting as an advanced energy conversion technology driven by sustainable energy is attracting ever-increasing attention for clean hydrogen fuel generation from water. Two fundamental reactions, hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), are involved, and cost-effective catalysts are required to fulfill the energy transfer process. Non-precious-metal catalysts have been proposed as the mainstay for future commercial applications. Among them, iron–nickel (FeNi)-based catalysts are very promising benefiting from the FeNi synergistic interaction in promoting the basic reactions. With the help of rational structure design, composition optimization, and electronic state tuning, advanced catalysts based on FeNi have been extensively reported. Herein, we focus on the varied FeNi-based catalysts for water splitting reactions. Before reviewing the literature, some descriptors and perspective comments are first given in the parameter evaluation part that might be helpful for understating the catalytic capability. In light of the extensive reports, some typical examples of FeNi-based catalysts classified into FeNi-alloy, phosphides, oxides, layered double hydroxides, sulfides, tellurides, selenides, and fluorides are introduced in detail. Combined with these advanced catalysts and the performance evaluation, this review will be helpful for readers in understanding the advanced progress on FeNi-based catalysts for water splitting reaction. Problems and challenges are also discussed demonstrating that efficient catalysts that can maintain high activity and stability are still highly desired. A brief perspective on FeNi-based catalysts is proposed that we hope can be a good complement to the existing literature for a better understanding of FeNi-based catalysts for water splitting reaction.

A Review on Advanced FeNi-Based Catalysts for Water Splitting Reaction

Selective structure transformation for NiFe/NiFe2O4 embedded porous nitrogen-doped carbon nanosphere with improved oxygen evolution reaction activity

Single-atom catalysts based on metal-N4 moieties and anchored on carbon supports (defined as M-N-C) are promising for oxygen reduction reaction (ORR). Among those, M-N-C catalysts with 4d and 5d transition metal (TM4d,5d) centers are much more durable and not susceptible to the undesirable Fenton reaction, especially compared with 3d transition metal based ones. However, the ORR activity of these TM4d,5d-N-C catalysts is still far from satisfactory; thus far, there are few discussions about how to accurately tune the ligand fields of single-atom TM4d,5d sites in order to improve their catalytic properties. Herein, we leverage single-atom Ru-N-C as a model system and report an S-anion coordination strategy to modulate the catalyst's structure and ORR performance. The S anions are identified to bond with N atoms in the second coordination shell of Ru centers, which allows us to manipulate the electronic configuration of central Ru sites. The S-anion-coordinated Ru-N-C catalyst delivers not only promising ORR activity but also outstanding long-term durability, superior to those of commercial Pt/C and most of the near-term single-atom catalysts. DFT calculations reveal that the high ORR activity is attributed to the lower adsorption energy of ORR intermediates at Ru sites. Metal-air batteries using this catalyst in the cathode side also exhibit fast kinetics and excellent stability.

Hui Liu

Papers

Efficient synergism of NiSe2 nanoparticle/NiO nanosheet for energy-relevant water and urea electrocatalysis

Efficient catalysis of N doped NiS/NiS2 heterogeneous structure

A Review on Advanced FeNi-Based Catalysts for Water Splitting Reaction

Selective structure transformation for NiFe/NiFe2O4 embedded porous nitrogen-doped carbon nanosphere with improved oxygen evolution reaction activity

Altering Ligand Fields in Single-Atom Sites through Second-Shell Anion Modulation Boosts the Oxygen Reduction Reaction.