Rhodium–Tin Binary Nanoparticle—A Strategy to Develop an Alternative Electrocatalyst for Oxygen Reduction

Ultrasonic-assisted hydrothermal synthesis of RhCu alloy nanospheres for electrocatalytic urea production

Herein, the electronic structure of RhCu nanospheres was optimized and the size of the nanoparticles was reduced by an ultrasonic-assisted hydrothermal method. The performance of electrocatalytic urea synthesis was improved with an enhanced faradaic efficiency and urea yield rate of 34.82 ± 2.47% and 26.81 ± 0.62 mmol g^-1 h^-1, respectively. This work opens a novel insight into synthesizing an electrocatalyst by ultrasonic treatment for urea production.

Electronegativity-Induced Charge Balancing to Boost Stability and Activity of Amorphous Electrocatalysts

Amorphization is an efficient strategy to activate intrinsically inert catalysts. However, the low crystallinity of amorphous catalysts often causes high solubility and poor electrochemical stability in aqueous solution. Here, a different mechanism is developed to simultaneously stabilize and activate the water-soluble amorphous MoS_x O_y via a charge-balancing strategy, which is induced by different electronegativity between the co-dopants Rh (2.28) and Sn (1.96). The electron-rich Sn prefers to stabilize the unstable apical O sites in MoS_x O_y through charge transfer, which can prevent the H from attacking. Meanwhile, the Rh, as the charge regulator, shifts the main active sites on the basal plane from inert Sn to active apical Rh sites. As a result, the amorphous RhSn-MoS_x O_y exhibits drastic enhancement in electrochemical stability (η₁₀ increases only by 12 mV) after 1000 cycles and a distinct activity (η₁₀ : 26 mV and Tafel: 30.8 mV dec^-1 ) for the hydrogen evolution reaction in acidic solution. This work paves a route for turning impracticably water-soluble catalysts into treasure and inspires new ideas to design high-performance amorphous electrocatalysts.

Electronic Asymmetric Distribution of RhCu Bimetallic Nanocrystals for Enhancing Trifunctional Electrocatalysis

Developing efficient and durable multifunctional electrocatalysts for oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR) is of significant importance for many electrochemical energy devices, such as water electrolyzers, metal-air batteries, and fuel cells. Herein, the Rh-Cu alloy nanocrystals (NCs) are prepared with a simple wet-chemical approach. The tuning of morphology and the asymmetric electron distribution provide more efficient Rh-Cu bimetallic sites. Meanwhile, the incorporation of Cu into the Rh lattice could reduce the oxidation of Rh-Cu bimetallic sites and increase the catalytic stability. Under the tuning of the composition, the drastically enhanced electrocatalytic activities of HER, OER, and ORR are achieved in the Rh₆Cu₁ NCs with the cell voltage required to be as low as 1.55 V to accomplish an overall water splitting of 10 mA cm^-2 and a maximum power density of 142.58 mW cm^-2 for a zinc-air battery with good stability, representing the best trifunctional electrocatalysts for all we know. This work highlights the design and control of Rh-Cu NCs, which could be a potential alternative approach to trifunctional catalysis and further boosts the development of the bimetallic electrocatalysts in the energy conversion system.

Controllable synthesis of Ir(Rh)–Sn/SiO2 bimetallic catalysts via surface organometallic chemistry for the production of ethanol from hydrogenolysis of ethyl acetate

A series of highly active Ir–Sn/SiO₂ and Rh–Sn/SiO₂ catalysts for ethyl acetate hydrogenolysis to ethanol were prepared from the grafting synthesis based on the surface organometallic chemistry concept.

Electrochemical Dealloying-Assisted Surface-Engineered Pd-Based Bifunctional Electrocatalyst for Formic Acid Oxidation and Oxygen Reduction

Synthesis of non-Pt bifunctional electrocatalyst for the anodic oxidation of liquid fuel and cathodic reduction of oxygen is of great interest in the development of energy conversion devices. We demonstrate a facile room-temperature synthesis of surface-engineered trimetallic alloy nanoelectrocatalyst based on Co, Cu, and Pd by thermodynamically favorable transmetallation reaction and electrochemical dealloying. The quasi-spherical Co _xCu _yPd _z trimetallic catalysts were synthesized by the thermodynamically favorable reaction of K₂PdCl₄ with sheetlike Co _mCu _n bimetallic alloy nanostructure. The surface engineering of Co _xCu _yPd _z was achieved by electrochemical dealloying. The surface-engineered alloy electrocatalyst exhibits excellent bifunctional activity toward formic acid oxidation reaction (FAOR) and oxygen reduction reaction (ORR) at same pH. The elemental composition and lattice strain control the electrocatalytic performance. The elemental composition-dependent compressive strain weakens the adsorption of oxygen-containing species and favors the facile electron transfer for FAOR and ORR. The engineered alloy electrocatalyst of Co_0.02Cu_13.8Pd_86.18 composition is highly durable and delivers high mass-specific activity for ORR and FAOR. It delivers mass-specific activities of 1.50 and 0.202 A/mg_Pd for FAOR and ORR, respectively, in acidic pH. The overall performance is superior to that of as-synthesized Pd and dealloyed bimetallic Co_2.7Pd_97.3 and Cu_5.61Pd_94.39 nanoelectrocatalysts.

Dendritic defect-rich palladium-copper-cobalt nanoalloys as robust multifunctional non-platinum electrocatalysts for fuel cells

Recently, the development of high-performance non-platinum electrocatalysts for fuel cell applications has been gaining attention. Palladium-based nanoalloys are considered as promising candidates to substitute platinum catalysts for cathodic and anodic reactions in fuel cells. Here, we develop a facile route to synthesize dendritic palladium–copper–cobalt trimetallic nanoalloys as robust multifunctional electrocatalysts for oxygen reduction and formic acid oxidation. To the best of our knowledge, the mass activities of the dendritic Pd₅₉Cu₃₀Co₁₁ nanoalloy toward oxygen reduction and formic acid oxidation are higher than those previously reported for non-platinum metal nanocatalysts. The Pd₅₉Cu₃₀Co₁₁ nanoalloys also exhibit superior durability for oxygen reduction and formic acid oxidation as well as good antimethanol/ethanol interference ability compared to a commercial platinum/carbon catalyst. The high performance of the dendritic Pd₅₉Cu₃₀Co₁₁ nanoalloys is attributed to a combination of effects, including defects, a synergistic effect, change of d-band center of palladium, and surface strain.

Fuel cells are promising for sustainable energy generation, but are limited by the performance of electrocatalysts. Here the authors synthesize dendritic palladium–copper–cobalt nanoalloys with electrocatalytic activity for oxygen reduction and formic acid oxidation as well as alcohol tolerance.