Engineering topics

Lu, Ruihu

Publications and source records attributed to Lu, Ruihu.

6 records

DOE OSTI2024

Zn 2+ -mediated catalysis for fast-charging aqueous Zn-ion batteries

Rechargeable aqueous zinc-ion batteries (AZIBs), renowned for their safety, high energy density and rapid charging, are prime choices for grid-scale energy storage. Historically, ion-shuttling models centring on ion-migration behaviour have dominated explanations for charge/discharge processes in aqueous batteries, like classical ion insertion/extraction and pseudocapacitance mechanisms. However, these models struggle to account for the exceptional performance of AZIBs compared to other aqueous metal-ion batteries. Here, in this study, we present a catalysis model elucidating the Zn 2+ anomaly in aqueous batteries, explaining it through the concept of adsorption in catalysis. Such behaviour can serve the charge/discharge role, predominantly dictated by solvated metal cations and cathode materials. First-principles calculations suggest optimal adsorption/desorption behaviour (water dissociation process) with the Zn 2+ -vanadium nitride (VN) combination. Experimentally, AZIBs implementing VN cathodes demonstrate fast-charging kinetics, showing a capacity of 577.1 mAh g -1 at a current density of 300,000 mA g -1 . The grasp of catalysis steps within AZIBs can drive solutions beyond state-of-the-art fast-charging batteries.

25 ENERGY STORAGE↗

DOE OSTI2024

Enhanced Carbon‐Carbon Coupling at Interfaces with Abrupt Coordination Number Changes

Abstract Cu‐catalyzed electrochemical CO 2 reduction reaction (CO 2 RR) produces multi‐carbon (C 2+ ) chemicals with considerable selectivities and activities, yet required high overpotentials impede its practical application. Here, we design interfaces with abrupt coordination number (CN) changes that greatly reduce the applied potential for achieving high C 2+ Faradaic efficiency (FE). Encouraged by the mechanistic finding that the coupling between *CO and *CO(H) is the most probable C−C bond formation path, we use Cu 2 O‐ and Cu‐phthalocyanine‐derived Cu (OD−Cu and PD−Cu) to build the interface. Using operando X‐ray absorption spectroscopy (XAS), we find that the Cu CN of OD−Cu is ~11, favoring CO* adsorption, while the PD−Cu has a COH*‐favorable CN of ~4. Operando Raman spectroscopy revealed that the interfaces with abrupt CN changes promote *OCCOH formation. As a result, the designed catalyst achieves a C 2+ FE of 85±2 % at 220 mA cm −2 in a zero‐gap CO 2 electrolyzer. An improvement of C 2+ FE by 3 times is confirmed at the low potential regime where the current density is 60–140 mA cm −2 , compared to bare OD−Cu. We report a 45‐h stable CO 2 RR operation at 220 mA cm −2 , producing a C 2+ product FE of ~80 %.

Chemistry↗

DOE OSTI2023

Fluorinated Interphase Enables Reversible Zn 2+ Storage in Aqueous ZnSO 4 Electrolytes

Aqueous zinc-ion batteries (AZIBs) using ZnSO 4 aqueous electrolytes complement Li-ion batteries and offer high safety, low cost, and scalability. However, an inferior cycle life, attributed to the generation of basic layered double hydroxides (LDHs) on the cathode during cycling, hampers the development of AZIBs. Although Zn(CF 3 SO 3 ) 2 (Zn(OTf) 2 ) electrolytes demonstrate exceptional performance, their higher cost in comparison to ZnSO 4 offsets their electrochemical stability benefits. Toward this end, we propose a fluorinated interphase strategy to achieve a stable battery with ZnSO 4 electrolytes by in situ pre-constructing the cathode-electrolyte interphase (CEI) of ZnOTf-LDH on the cathode surface. Unlike ZnSO 4 - LDH, which obstructs the diffusion channel of zinc ions, ZnOTf-LDH facilitates the desolvation of zinc ions, thereby enhancing the cycling stability (over 50 cycles at a low current density of 200 mA g -1 ). Further, this work offers valuable insights into the degradation mechanism of AZIBs and provides an effective approach for developing stable and low-cost AZIBs.

25 ENERGY STORAGE↗

DOE OSTI2023

Hierarchically Porous Carbons with Highly Curved Surfaces for Hosting Single Metal FeN 4 Sites as Outstanding Oxygen Reduction Catalysts

Iron–nitrogen–carbon (Fe₋N₋C) materials have emerged as a promising alternative to platinum-group metals for catalyzing the oxygen reduction reaction (ORR) in proton-exchange-membrane fuel cells. However, their low intrinsic activity and stability are major impediments. Herein, an Fe₋N–C electrocatalyst with dense FeN 4 sites on hierarchically porous carbons with highly curved surfaces (denoted as FeN 4 - hc C) is reported. The FeN 4 - hc C catalyst displays exceptional ORR activity in acidic media, with a high half-wave potential of 0.85 V (versus reversible hydrogen electrode) in 0.5 m H 2 SO 4 . When integrated into a membrane electrode assembly, the corresponding cathode displays a high maximum peak power density of 0.592 W cm -2 and demonstrates operating durability over 30 000 cycles under harsh H 2 /air conditions, outperforming previously reported Fe–N₋C electrocatalysts. These experimental and theoretical studies suggest that the curved carbon support fine-tunes the local coordination environment, lowers the energies of the Fe d-band centers, and inhibits the adsorption of oxygenated species, which can enhance the ORR activity and stability. This work provides new insight into the carbon nanostructure–activity correlation for ORR catalysis. It also offers a new approach to designing advanced single-metal-site catalysts for energy-conversion applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2023

Tailoring activity of iron phthalocyanine by edge-nitrogen sites induced electronic delocalization

Fe-N-C catalysts have been recognized as the most satisfactory candidates alternatively to Pt-based catalysts for oxygen reduction reaction (ORR). However, fine-tailoring of their intrinsic ORR catalytic activity still remains a great challenge due to the inferior accessibility and intrinsic activity of FeN x moieties. Herein, one order of magnitude activity enhancement of pristine Fe-N-C through cooperating with nitrogen-doped carbon micro-flower is achieved. The axial coordination effect between Fe active center and nitrogen atoms in support can break the electronic distribution symmetry of FeN x moieties and induce the electron delocalization on Fe active center and the electron localization on N, respectively, which favor the adsorption behavior of *OH intermediate. As a result, the catalyst exhibits a remarkable half-wave potential of 0.9 V and a high kinetic current density of 74.04 mA cm -2 at 0.85 V. In addition, when utilized as a cathode catalyst of liquid Zn-air batteries (ZABs), it possesses excellent electrochemical performance, for example, a high open circuit voltage (OCV) and peak power density of 1.59 V and 170.09 mW cm -2 , respectively. In conclusion, this work provides a new understanding into the activity enhancement mechanism of Fe-N-C catalysts, and inspires electronic delocalization of active sites for adjusting catalytic activity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2023

Coordination Polymer Electrocatalysts Enable Efficient CO‐to‐Acetate Conversion

Abstract Upgrading carbon dioxide/monoxide to multi‐carbon C 2+ products using renewable electricity offers one route to more sustainable fuel and chemical production. One of the most appealing products is acetate, the profitable electrosynthesis of which demands a catalyst with higher efficiency. Here, a coordination polymer (CP) catalyst is reported that consists of Cu(I) and benzimidazole units linked via Cu(I)‐imidazole coordination bonds, which enables selective reduction of CO to acetate with a 61% Faradaic efficiency at −0.59 volts versus the reversible hydrogen electrode at a current density of 400 mA cm −2 in flow cells. The catalyst is integrated in a cation exchange membrane‐based membrane electrode assembly that enables stable acetate electrosynthesis for 190 h, while achieving direct collection of concentrated acetate (3.3 molar) from the cathodic liquid stream, an average single‐pass utilization of 50% toward CO‐to‐acetate conversion, and an average acetate full‐cell energy efficiency of 15% at a current density of 250 mA cm −2 .

Luo, Mingchuan↗