Performance regulation strategies of Ru-based nitrogen reduction electrocatalysts

doi:10.11949/0438-1157.20230048

Abstract

Abstract:

Ammonia is an important chemical and ideal energy vector. Artificial ammonia synthesis through the Haber-Bosch (H-B) process is energy-intensive. In contrast, ammonia is generated from N₂ and H₂O under mild conditions through the electrocatalytic ammonia synthesis. Ru-based catalyst performs superior activities during the nitrogen reduction reaction (NRR), which has attracted extensive attention. However, its development is limited owing to its scarcity. Therefore, the NRR reaction mechanisms are briefly outlined and a systematic summary of Ru-based electrocatalysts for ammonia synthesis is introduced firstly. Subsequently, it is methodically discussed how the strategies for performance enhancement (structural optimization, surface/interface engineering, defect engineering) of catalysts regulate the active sites or electronic structure and then promote the activity of catalysts. Finally, the remaining challenges of Ru-based electrocatalysts in future are highlighted. This review aims to achieve the usage of the Ru metal effectively through the performance-improving strategies of Ru-based electrocatalysts and provides the theory guidance for the design of the other NRR catalysts.

Key words: catalyst, catalysis, electrochemistry, ammonia synthesis, nitrogen reduction reaction, performance-improving strategies

摘要：

氨是重要的化学品以及理想的能源载体，人工合成氨主要来源于高能耗的Haber-Bosch（H-B）工艺。相比而言，电催化合成氨以N₂和H₂O为原料，实现了温和条件下产氨。Ru基催化剂在氮还原（NRR）过程中表现出优异的催化活性，但由于较为稀缺限制了其发展。基于此，首先概述了NRR的反应机制并对现有的Ru基合成氨电催化剂进行了系统的介绍；详细分析了性能提升策略（结构调控、表/界面工程、缺陷工程），如何调控活性组分或电子结构，进而提升催化剂的性能；最后分析了Ru基催化剂所面临的挑战。旨在通过Ru基催化剂性能提升策略，实现贵金属Ru的高效利用，并为其他NRR催化剂的开发设计提供指导。

关键词: 催化剂, 催化, 电化学, 合成氨, 氮还原反应, 性能提升策略

CLC Number:

O 643.36

Tan ZHANG, Guang LIU, Jinping LI, Yuhan SUN. Performance regulation strategies of Ru-based nitrogen reduction electrocatalysts[J]. CIESC Journal, 2023, 74(6): 2264-2280.

张谭, 刘光, 李晋平, 孙予罕. Ru基氮还原电催化剂性能调控策略[J]. 化工学报, 2023, 74(6): 2264-2280.

Figures/Tables 11

Fig.1 Roadmap of ammonia as energy carrier via ammonia synthesis and decomposition[1]

Fig.2 Strategies to improve the performance of Ru-based electrocatalysts

Fig.3 Reaction mechanisms for NRR on heterogeneous catalysts[23]

Fig.4 FTIR spectra on the Ru thin film in the different N2-saturated solutions[28]

Table 1 Summary of performance of partial Ru-based catalysts guided by performance-improving strategies

序号	催化剂	产氨率	FE/%	电解液	电位/V(vs RHE)	文献	调控策略
1	LaFeO₃-Ru	137.5 μg·h^-1·mg^-1	56.9	0.1 mol·L^-1 K₂SO₄	-0.7	[36]	单原子策略
2	Ru SAs/g-C₃N₄	23.0 μg·h^-1·mg^-1	8.3	0.5 mol·L^-1 NaOH	0.05	[40]
3	Ru SAs/N-C	120.9 μg·h^-1·mg^-1	29.6	均可	-0.2	[45]
4	SA Ru-Mo₂CT _x	40.57 μg·h^-1·mg^-1	25.77	0.5 mol·L^-1 K₂SO₄	-0.3	[55]
5	Ru SAs/Ti₃C₂O	27.56 μg·h^-1·mg^-1	23.3	0.1 mol·L^-1 HCl	-0.2	[56]
6	PdRu TPs	37.23 μg·h^-1·mg^-1	1.85	0.1 mol·L^-1 KOH	-0.2	[80]	形貌/晶体调控策略
7	PdRu BPNs	25.92 μg·h^-1·mg^-1	1.53	0.1 mol·L^-1 HCl	-0.1	[24]
8	mRhRu/NF	30.28 μg·h^-1·mg^-1	28.33	0.1 mol·L^-1 Na₂SO₄	-0.05	[84]
9	a₁-Ru/CNTs	10.49 μg·h^-1·mg^-1	17.48	5 mmol·L^-1 Cs₂CO₃	-0.2	[34]
10	Ru/rGO-C12	50 μg·h^-1·mg^-1	11	0.05 mol·L^-1 H₂SO₄	-0.1	[93]	表/界面工程
11	RuCu-FNs	53.6 μg·h^-1·mg^-1	7.2	0.1 mol·L^-1 HCl	-0.1	[103]	表/界面工程
12	Ru₈₈Pt₁₂	47.4 μg·h^-1·mg^-1	8.9	0.1 mol·L^-1 KOH	-0.2	[111]	杂原子掺杂
13	Rh_0.6Ru_0.4 NAs/CP	57.75 μg·h^-1·mg^-1	3.39	0.1 mol·L^-1 Na₂SO₄	-0.2	[112]
14	Ru-Cu NPs	73 μg·h^-1·cm^-2	30.95	0.1 mol·L^-1 HCl	-0.1	[114]
15	Ru₂P-rGO	32.8 μg·h^-1·mg^-1	13.04	0.1 mol·L^-1 HCl	-0.05	[117]
16	Ru/CeO₂-Vo	9.87×10^-8 mmol·s^-1·cm^-2	11.7	0.05 mol·L^-1 H₂SO₄	-0.25	[125]	空位调控
17	Ru/2H-MoS₂	1.14×10^-10 mmol·s^-1·cm^-2	17.6	10 mmol·L^-1 HCl	-0.15	[127]	空位调控

Fig.5 (a) Morphology and structure characterization of Ru@ZrO2/NC; (b) Electrochemical nitrogen reduction activities; (c) Calculation models and free energy diagrams for NRR [44]

Fig.6 (a) The corresponding elemental mapping images of a single PdRu TP; (b) NH3 yield rates and FE of PdRu TPs at selected potentials; (c) NH3 yield rates of different catalysts at -0.2 V(vs RHE); (d) Schematic diagram of electrocatalytic NRR process on the PdRu TPs[80]

Fig.7 (a) Illustration of synthesis and modification of Ru/rGO with aliphatic thiols; (b) TEM images; (c) HR-TEM images; (d) FE and rate of NH3 production for Ru/rGO-C12; (e) Recyclability and (f) long-term stability of Ru/rGO-C12; (g) NH3 quantification by 1H NMR in 15N2 environment; (h) The optimized atomic configuration; (i) Bader charge distribution; (j) Gibbs free energy profile of NRR on Ru/rGO-C12 [93]

Fig.8 (a) A schematic diagram of the structure of a Ru88Pt12 nanowire; (b) TEM images and (c) HAADF images of Ru88Pt12 nanowires; (d) NH3 production rates and (e) corresponding FE at different potentials; (f) Recyclability and (g) long-term stability of electrocatalysis; (h) Atomic models; (i) Calculated adsorption energies; (j) Projected density of states[111]

Fig.9 (a) Schematic diagram of the structure and fabrication of Ru-Cu NPs; (b) Mapping images of Ru-Cu NPs; (c) FE and NH3 formation rates; (d) 1H NMR spectra; (e) DFT calculations of the NRR process on the electrocatalysts[114]

Fig.10 (a) EPR spectra; (b) XPS spectra of O 1s; (c) Valance bands; (d) Schematic diagram of minimum-energy pathway for electrochemical N2 conversion into NH3 catalyzed by Ru/2H-MoS2 material[125, 127]

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