Interplay between Nitrogen Concentration, Structure, Morphology, and Electrochemical Performance of PdCoNi “Core-Shell” Carbon Nitride Electrocatalysts for the Oxygen Reduction Reaction

Palladium nanoparticles loaded on nitrogen and boron dual-doped single-wall carbon nanohorns with high electrocatalytic activity in the oxygen reduction reaction

Palladium nanoparticles with a diameter of 2-4 nm supported on nitrogen and boron dual-doped single-wall carbon nanohorns (Pd-NBCNHs) are synthesized via a one-step method and their electrocatalytic activities are investigated for the oxygen reduction reaction (ORR) in alkaline media. The electrochemical results demonstrate that the oxygen reduction peak potential of Pd-NBCNHs is similar to that of commercial 20% Pt-C. Furthermore, Pd-NBCNHs show a more positive half-wave potential than 20% Pt-C and display better long-term stability and resistance to methanol than 20% Pt-C, which is attributed to the synergetic effect of the Pd nanoparticles and NBCNHs. As NBCNHs have abundant pyrrolic nitrogen, charged sites and defective structures, they not only act as a carrier, but also provide the active sites for oxygen adsorption during the oxygen reduction reaction process. The outstanding electrochemical performance makes Pd-NBCNHs promising to be applied in fuel cells.

Carbon Nitride Materials as Efficient Catalyst Supports for Proton Exchange Membrane Water Electrolyzers

Carbon nitride materials with graphitic to polymeric structures (gCNH) were investigated as catalyst supports for the proton exchange membrane (PEM) water electrolyzers using IrO₂ nanoparticles as oxygen evolution electrocatalyst. Here, the performance of IrO₂ nanoparticles formed and deposited in situ onto carbon nitride support for PEM water electrolysis was explored based on previous preliminary studies conducted in related systems. The results revealed that this preparation route catalyzed the decomposition of the carbon nitride to form a material with much lower N content. This resulted in a significant enhancement of the performance of the gCNH-IrO₂ (or N-doped C-IrO₂) electrocatalyst that was likely attributed to higher electrical conductivity of the N-doped carbon support.

First-Row Transition Metal Based Catalysts for the Oxygen Evolution Reaction under Alkaline Conditions: Basic Principles and Recent Advances

Owing to its abundance, high gravimetric energy density, and environmental friendliness, hydrogen is a promising renewable energy to replace fossil fuels. One of the most prominent routes toward hydrogen acquisition is water splitting, which is currently bottlenecked by the sluggish kinetics of oxygen evolution reaction (OER). Numerous of electrocatalysts have been developed in the past decades to accelerate the OER process. Up to now, the first-row transition metal based compounds are in pole position under alkaline conditions, which have become subjects of extensive studies. Recently, significant advances in providing compelling catalytic performance as well as exploring their catalytic mechanisms have been achieved in this area. In this review, we summarized the fundamentals and recent progresses in first-row transition metal based OER catalysts, with special emphasis on the pathways of promoting catalytic performance by concrete strategies. New insight into material design, particularly the role of experimental approaches in the electrocatalytic performance and reaction mechanisms of OER are expected to be provided.

Metallic Cobalt@Nitrogen-Doped Carbon Nanocomposites: Carbon-Shell Regulation toward Efficient Bi-Functional Electrocatalysis

To advance hydrogen economy, noble-metal-free electrocatalysts with good efficiency are urgently demanded. They can be developed from metal-organic frameworks (MOFs) with abundant structure-variety, in which a controlled pyrolysis is desired to rationalize nanostructure and maximize catalytic activity. Herein, the efficient regulation is proposed for the first time on the carbon-shell of MOFs-derived Co@NC nanocomposites via varying temperature and flow-rate during pyrolysis, enabling the good accessibility and the electronic optimization of active Co cores. With moderated temperature and flow-rate, the resulting ultrathin carbon-shell, on the one hand, renders Co cores easily accessible to electrolytes and, on the other hand, promotes the electronic penetration to optimize metallic Co active sites. As expected, the optimal Co@NC affords the benchmarking performance of noble-metal-free electrocatalysts in hydrogen evolution and oxygen reduction reactions, featured by the low overpotentials, the striking kinetic metrics, and the outstanding long-term stability. Elucidating the feasibility to design efficient electrocatalysts via controlled MOFs pyrolysis, this work will open up new opportunities for the development of cost-effective materials in the energy field.

Cobalt disulfide/graphite foam composite films as self-standing electrocatalytic electrodes for overall water splitting

A unique inter-layer porous 3D cobalt disulfide/graphite foam (CoS₂/GF) electrocatalytic electrode exhibits superior performance for overall water splitting.

Sacrificial Reducing Agent Free Photo-Generation of Platinum Nano Particle over Carbon/TiO2 for Highly Efficient Oxygen Reduction Reaction

Electrocatalytic materials for oxygen reduction reaction, currently dominated by platinum/carbon catalyst is marred by drawbacks such as use of copious amount of Pt and use of “non-green” sacrificial reducing agent (SRA) during its synthesis. A single stroke remedy for these two problems has been achieved through an in-situ aqueous photoreduction void of even trace amounts of SRA with an enhanced activity. Reduction of PtCl₆²⁻ salt to Pt nano particles on carbon substrate was achieved solely using solar spectrum as the source of energy and TiO₂ as photocatalyst. Here, we demonstrate that this new procedure of photoreduction, decorates Pt over different types of conducting allotropes with the distribution and the particle size primarily depending on the conductivity of the allotrope. The Pt/C/TiO₂ composite unveiled an ORR activity on par to the most efficient Pt based electrocatalyst prepared through the conventional sacrificial reducing agent aided preparation methods.

Growth of One-Dimensional RuO2 Nanowires on g-Carbon Nitride: An Active and Stable Bifunctional Electrocatalyst for Hydrogen and Oxygen Evolution Reactions at All pH Values

Development of highly efficient and durable bifunctional electrocatalyst for hydrogen and oxygen evolution reactions (HER and OER) is essential for efficient solar fuel generation. The commercial RuO₂ or RuO₂-based catalysts are highly active toward OER, but their poor stability under different operating conditions is the main obstacle for their commercialization. Herein, we report growth of one-dimensional highly crystalline RuO₂ nanowires on carbon nitride (1D-RuO₂-CN_x) for their applications in HER and OER at all pH values. The 1D-RuO₂-CN_x, as an OER catalyst, exhibits a low onset overpotential of ∼200 mV in both acidic and basic media, whereas Tafel slopes are 52 and 56 mV/dec in acidic and basic media, respectively. This catalyst requires a low overpotential of 250 and 260 mV to drive the current density of 10 mA cm^-2 in acidic and basic media, respectively. The mass activity of 1D-RuO₂-CN_x catalyst is 352 mA mg^-1, which is ∼14 times higher than that of commercial RuO₂. Most importantly, the 1D-RuO₂-CN_x catalyst has remarkably higher stability compared to commercial RuO₂. This catalyst also exhibits superior HER activity with a current density of 10 mAcm^-2 at ∼93 and 95 mV in acidic and basic media. The HER Tafel slopes of this catalyst are 40 mV/dec in acidic condition and 70 mV/dec in basic condition. The HER activity of this catalyst is slightly lower than Pt/C in acidic media, whereas in basic media it is comparable or even better than that of Pt/C at higher overpotentials. The HER stability of this catalyst is also better than that of Pt/C in all pH solutions. This superior catalytic activity of 1D-RuO₂-CN_x composite can be attributed to catalyst-support interaction, enhanced mass and electron transport, one-dimensional morphology, and highly crystalline rutile RuO₂ structure.

Nitrogen-doped heterostructure carbon functionalized by electroactive organic molecules for asymmetric supercapacitors with high energy density

The organic molecules (TCBQ, AQ) with multi-electron redox center are selected to modify nitrogen-doped heterostructure carbon (NHC) by noncovalent interaction and the electrode materials show good performances and potential self-matching behaviors.

Magnesium cobalt silicate as a bifunctional catalyst for the O2 electrode and its application in Li–O2 cells

MgCoSiO₄ is synthesized by using mixed solvothermal approach and studied for oxygen evolution (OER) and reduction (ORR) reactions. It is also studied for non-aqueous Li–O₂ cells.

Edge-to-edge interaction between carbon nanotube-pyrene complexes and electrodes for biosensing and electrocatalytic applications

We demonstrate here that the edge-to-edge interaction between carbon nanotubes (CNTs) and edge plane electrodes plays an important role in exposing a large proportion of the basal planes of the CNTs to allow enhanced π-π stacking of a pyrenyl compound and subsequent high density protein immobilization yielding large electrocatalytic currents.

Effect of component distribution and nanoporosity in CuPt nanotubes on electrocatalysis of the oxygen reduction reaction

Pt-based bimetallic electrocatalysts hold great potential in the oxygen reduction reaction (ORR) in current fuel-cell prototypes. However, they also face challenges from drastic dealloying of less-noble metals and coalescence of small nanoparticles. Porous and structure-ordered nanotubes may hold the potential to improve the stability of bimetallic electrocatalysts. Herein, we report a method to prepare CuPt nanotubes and porous Cu3 Pt intermetallic nanorods through a controlled galvanic replacement reaction and heat treatment process. The effect of the geometric features and compositional segregation on the electrocatalysis of the ORR was clarified. The outstanding performance of the Cu3 Pt/C-700 catalyst in the ORR relative to that of CuPt/C-RT was mainly attributed to the nanoporosity of the catalyst, whereas the enhanced specific activity on CuPt/C-RT after potential cycling was attributed to the interaction between the CuPt alloyed core and the Pt shell in the tube wall.

Sucrose-derived activated carbons: electron transfer properties and application as oxygen reduction electrocatalysts

ORR electrocatalysts derived from sugar: activated carbons derived from sucrose showed electrocatalytic activity for the oxygen reduction reaction.

The effect of structural dimensionality on the electrocatalytic properties of the nickel selenide phase

Synthesis of different morphologies of nickel selenide structures and their activities in various applications.

A chromium nitride/carbon nitride containing graphitic carbon nanocapsule hybrid as a Pt-free electrocatalyst for oxygen reduction

A CrN nanoparticle and carbon nitride containing graphitic carbon nanocapsule hybrid has been synthesized, which can be used as a highly-efficient Pt-free electrocatalyst towards oxygen reduction reaction with a dominant 4-electron pathway, superior stability and methanol immunity.

Cr effect on the durability of Pt–TM catalysts for PEMFCs

Pt–TM–Cr/C alloy catalysts were produced by a polyol method. We investigated the improvement of durability by the addition of a small amount of Cr, which is expected to prevent dissolution of transition metals.

Pyrolyzed egg yolk as an efficient bifunctional electrocatalyst for oxygen reduction and evolution reactions

A novel electrocatalyst of heteroatom-doped carbon (HDC) has been developed via facile pyrolysis of hen egg yolk without incorporating external heteroatoms.