Electronic Asymmetric Distribution of RhCu Bimetallic Nanocrystals for Enhancing Trifunctional Electrocatalysis

Abstract

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.

RuCoOx Nanofoam as a High-Performance Trifunctional Electrocatalyst for Rechargeable Zinc–Air Batteries and Water Splitting

“…The potential difference (Δ E ) (Δ E = E j 10 – E 1/2 ) of the OER and ORR was a general index to evaluate the bifunctionality of oxygen electrode catalysts. The RuCoO x electrocatalyst showed a small Δ E of 0.65 V (Figure S13), which was smaller than those of commercial Pt/C + IrO 2 , pure RuO 2 and Co 3 O 4 electrocatalysts, and outperformed nearly all of the advanced bifunctional oxygen catalysts ,− ,− (Figure g, Table S2).…”

“…It is quite challenging to achieve the target of half-wave potential (E 1/2 ) larger than 0.85 V for ORR, the overpotential at 10 mA cm −2 smaller than 300/50 mV for OER/HER at the same time. 28 Some researchers focus on the design of noble metal trifunctional electrocatalysts, including PtCo/Ir, 29 Rh 6 Cu, 30 etc. Although these catalysts can partially achieve some of the above targets, the high cost of these Pt/Ir/Rhbased materials significantly limits their wide applications.…”

Highly Active Hollow RhCu Nanoboxes toward Ethylene Glycol Electrooxidation

“…The former is ascribed to the oxidation of EG molecules, and the latter originates from the removal of carbonaceous intermediates. [ 24 ] The magnified CV curves in low potential region (Figure 4C) and mass activity plot (Figure 4D) show that solid RhCu nanocrystals have lower onset potential (0.35 V) and larger mass activity (401.3 A g Rh −1 ) than that of commercial Rh nanocrystals (0.51 V and 276.1 A g Rh −1 ), indicating that alloying Rh with Cu is favorable for improving the Rh utilization. [ 24 ] For RhCu nanoboxes, the peak potential and the onset potential of EGOR further negatively shift ≈67 and 40 mV relative to the solid RhCu nanocrystals, respectively.…”

“…[ 24 ] The magnified CV curves in low potential region (Figure 4C) and mass activity plot (Figure 4D) show that solid RhCu nanocrystals have lower onset potential (0.35 V) and larger mass activity (401.3 A g Rh −1 ) than that of commercial Rh nanocrystals (0.51 V and 276.1 A g Rh −1 ), indicating that alloying Rh with Cu is favorable for improving the Rh utilization. [ 24 ] For RhCu nanoboxes, the peak potential and the onset potential of EGOR further negatively shift ≈67 and 40 mV relative to the solid RhCu nanocrystals, respectively. Meanwhile, the mass activity of RhCu nanoboxes toward the EGOR is 775.1 A g Rh −1 , which is 1.9 and 2.8 times as large as that of solid RhCu nanocrystals and Rh nanocrystals, suggesting that the unique porous structure can effectively accelerate the reaction kinetics of EGOR.…”

“…It is well known that the alcohol electrooxidations require multiple steps to achieve the desirable products of CO 2 and H 2 O, and some intermediates such as CO can absorb on the electrocatalyst surface and hider the electrochemical reaction. [24,25] The higher the activity of electrocatalyst, the easier these intermediates leave from the electrocatalyst surface, which can be evaluated with the ratio of the peak current in positive (j p ) and negative (j n ) sweep CV curves. A larger j p /j n indicates less accumulation of intermediate products on active sites.…”