Shaofang Fu

Single-Atom Electrocatalysts

Recent years have witnessed a dramatic increase in the production of sustainable and renewable energy. However, the electrochemical performances of the various systems are limited, and there is an intensive search for highly efficient electrocatalysts by more rational control over the size, shape, composition, and structure. Of particular interest are the studies on single-atom catalysts (SACs), which have sparked new interests in electrocatalysis because of their high catalytic activity, stability, selectivity, and 100 % atom utilization. In this Review, we introduce innovative syntheses and characterization techniques for SACs, with a focus on their electrochemical applications in the oxygen reduction/evolution reaction, hydrogen evolution reaction, and hydrocarbon conversion reactions for fuel cells (electrooxidation of methanol, ethanol, and formic acid). The electrocatalytic performance is further considered at an atomic level and the underlying mechanisms are discussed. The ultimate goal is the tailoring of single atoms for electrochemical applications.

Facile One-Step Synthesis of Three-Dimensional Pd–Ag Bimetallic Alloy Networks and Their Electrocatalytic Activity toward Ethanol Oxidation

The three-dimensional palladium networks and palladium-silver bimetallic alloy networks were synthesized at room temperature on a large scale using a rapid and simple strategy. The results revealed that the morphology of the networks is not affected by the composition. We demonstrated that the as-prepared unsupported networks exhibited excellent electrochemical activity and stability toward ethanol oxidation reaction in alkaline media due to the formation of palladium-silver alloys as well as the porous nanostructures. The results indicate that the well-defined three-dimensional palladium-silver bimetallic alloy networks are promising catalysts for fuel cells.

One-pot synthesis of B-doped three-dimensional reduced graphene oxide via supercritical fluid for oxygen reduction reaction

There has been a great deal of interest recently in three-dimensional (3D) graphene based materials, as they exhibit large surface areas, unique electronic properties, and other attractive features. Particularly, 3D graphene doped with heteroatoms catalysts show high electrocatalytic activity toward oxygen reduction reaction (ORR), which can be used as metal-free catalysts. Most of the existing synthesis strategies of 3D graphene invariably involve multiple steps and procedures are often energy intensive and time-consuming. In this paper, we reported a one-pot and green method to synthesize boron-doped 3D reduced graphene oxide (B-3DrGO) using the supercritical carbon dioxide (ScCO2) technique. The resulting products exhibit hierarchical porous structures, leading to a high specific surface area of 541 m2 g−1. A high content of B (2.9 at%) was detected in the product, suggesting that B-doping was efficient using this technique. The B-3DrGO displays electrocatalytic activity toward ORR, which is comparable to the commercially available Pt/C (20 wt%) catalyst, in addition to their superior durability and resistance to the crossover effect. Moreover, the supercritical fluid technique, which uses non-flammable, essentially nontoxic, inexpensive, and environmentally benign CO2, is a new and green approach for the synthesis of heteroatom doped 3D graphene.

Efficient Synthesis of MCu (M = Pd, Pt, and Au) Aerogels with Accelerated Gelation Kinetics and their High Electrocatalytic Activity

To accelerate hydrogel formation and further simplify the synthetic procedure, a series of MCu (M = Pd, Pt, and Au) bimetallic aerogels is synthesized from the in situ reduction of metal precursors through enhancement of the gelation kinetics at elevated temperature. Moreover, the resultant PdCu aerogel with ultrathin nanowire networks exhibits excellent electrocatalytic performance toward ethanol oxidation, holding promise in fuel-cell applications.

Facilely Tuning Porous NiCo2O4 Nanosheets with Metal Valence‐State Alteration and Abundant Oxygen Vacancies as Robust Electrocatalysts Towards Water Splitting

Great efforts in developing clean electrochemical water splitting technology leads to the rational design and synthesis of highly efficient oxygen evolution reaction (OER) catalysts with low overpotential and fast reaction kinetics. Herein, we focus on the role that morphology and composition play in the OER performance to rationally design freestanding 3D porous NiCo2O4 nanosheets with metal valence states alteration and abundant oxygen vacancies as robust electrocatalysts towards water splitting. Besides metal valence-state alteration, surface modification regarding the evolution of oxygen vacancies is facilely realized upon the sodium borohydride treatment, which is beneficial for the enhanced OER performance. Taking advantage of the porous nanostructures and abundant surface activity sites with high reactivity, the resultant nanostructures exhibit excellent OER activity and stability in alkaline electrolytes that outperform that of pristine NiCo2O4 and commercial RuO2, thus holding great potential for the water splitting.

Self-Assembled Fe-N-Doped Carbon Nanotube Aerogels with Single-Atom Catalyst Feature as High-Efficiency Oxygen Reduction Electrocatalysts

Self-assembled M-N-doped carbon nanotube aerogels with single-atom catalyst feature are for the first time reported through one-step hydrothermal route and subsequent facile annealing treatment. By taking advantage of the porous nanostructures, 1D nanotubes as well as single-atom catalyst feature, the resultant Fe-N-doped carbon nanotube aerogels exhibit excellent oxygen reduction reaction electrocatalytic performance even better than commercial Pt/C in alkaline solution.

Ultrasonic-assisted synthesis of Pd-Pt/carbon nanotubes nanocomposites for enhanced electro-oxidation of ethanol and methanol in alkaline medium.

Herein, a facile ultrasonic-assisted strategy was proposed to fabricate the Pd-Pt alloy/multi-walled carbon nanotubes (Pd-Pt/CNTs) nanocomposites. A good number of Pd-Pt alloy nanoparticles with an average of 3.4 ± 0.5 nm were supported on sidewalls of CNTs with uniform distribution. The composition of the Pd-Pt/CNTs nanocomposites could also be easily controlled, which provided a possible approach for the preparation of other architectures with anticipated properties. The Pd-Pt/CNTs nanocomposites were extensively studied by electron microscopy, induced coupled plasma atomic emission spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, and applied for the ethanol and methanol electro-oxidation reaction in alkaline medium. The electrochemical results indicated that the nanocomposites had better electrocatalytic activities and stabilities, showing promising applications for fuel cells.

Optimization of cobalt/nitrogen embedded carbon nanotubes as an efficient bifunctional oxygen electrode for rechargeable zinc–air batteries

The design of efficient, durable and affordable catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is indispensable in regenerative energy conversion and storage systems, such as water splitting, fuel cells and rechargeable metal–air batteries. Here we present a high-performance bifunctional catalyst with cobalt and nitrogen embedded carbon nanotubes (CNCNs), which exhibits high electrocatalytic activity towards the ORR and OER. For comparison, iron and nickel embedded carbon nanotubes (FeNCNs and NiNCNs) are also investigated to reveal the electrochemical performance upon transition metal doping. In the half-cell testing, FeNCN-44 and CNCN-100 show better electrochemical activities towards the ORR, while the compositionally optimized CNCN-44 outperforms other prepared catalysts during the OER including commercial RuO2 and Pt/C. The CNCN-44 exhibits a low oxidation overpotential of 0.38 V and stability with negligible deactivation over extended operation, which make it the best catalyst in overall bifunctional performance. We also test the suitability and durability of CNCN-44 as the oxygen electrode for rechargeable Zn–air batteries. The homemade battery exhibits a high open-circuit potential of 1.45 V and stable charge–discharge durability over 12 hours in 6 M KOH electrolyte at 10 mA cm−2, which make our compositionally optimized CNCN-44 a promising candidate as a cathode material for rechargeable zinc–air batteries.

One-step synthesis of cobalt and nitrogen co-doped carbon nanotubes and their catalytic activity for the oxygen reduction reaction

In this paper, cobalt and nitrogen co-doped carbon nanotubes were successfully synthesized by a simple thermal treatment method with dicyandiamide and cobalt(II) chloride hexahydrate. The as-synthesized nanostructures presented excellent catalytic activity and stability toward the oxygen reduction reaction in alkaline solution. Especially, when the molar ratio between dicyandiamide and cobalt(II) chloride hexahydrate was 22:1, the catalyst showed a close onset potential, half-wave potentials and limiting current density compared to the commercial platinum/carbon catalyst, which might be attributable to the formation of pyridinic and quaternary nitrogen functional groups as well as the incorporation of cobalt during the thermal treatment. Moreover, the as-synthesized catalyst exhibited good tolerance to the methanol crossover effect.

Ultrasonic-assisted synthesis of carbon nanotube supported bimetallic Pt–Ru nanoparticles for effective methanol oxidation

In this paper, we demonstrate a facile and one-step ultrasonic method to synthesize a carboxylate functionalized multi-walled carbon nanotube supported bimetallic platinum ruthenium nanoparticle (Pt–Ru/c-MWNT) catalyst. The results show that the atomic Pt–Ru ratio is approximately 1 : 1, and the Pt mass loading in the catalyst is 8%. In addition, Pt–Ru nanoparticles with bimetallic structure, ultrasmall size (1.9 nm), and uniform distribution were well-dispersed onto the surface of c-MWNTs, which exhibit enhanced electrocatalytic performance toward methanol oxidation. It is found that this catalyst has a much higher electrochemically active surface area (ECSA) (133.2 m2 gPt−1) and current density for methanol oxidation (1236.0 mA mgPt−1) than those of commercial Pt/C (20 wt%) (55.6 m2 gPt−1, 214.2 mA mgPt−1). Furthermore, the oxidation current density of the Pt–Ru/c-MWNT catalyst at 10 000 s is 22.5 mA mgPt−1, which indicates a long-term high electrocatalytic activity of the Pt–Ru/c-MWNT catalyst for methanol oxidation in acid media.