High-performance Electrocatalysts Research Articles

Tetrametallic mastery: Cluster-doped graphdiyne as a superior electrocatalyst for hydrogen evolution

Hydrogen evolution reaction (HER) is a promising route for sustainable hydrogen production. However, its efficiency is limited by kinetic barriers. Herein, we employ density functional theory (DFT) calculations to demonstrate a new strategy of embedding tetrametallic transition metal clusters (3TM1-TM2) into the pores of graphdiyne (GDY) to effectively optimize its HER performance. By screening 900 configurations, 10 prototypes displayed near-ideal hydrogen adsorption free energies. Among them, 3W–Hg@GDY with a ΔGH of −0.00035 eV was identified as the optimal candidate. Analysis of the electronic structure reveals hybridization between the metal d orbitals and GDY p orbitals near the Fermi level, creating partially filled impurity states to promote hydrogen adsorption. Additionally, coordination between the three TM1 atoms and active TM2 atom in the cluster enables precise tuning of TM2's electron density to achieve a moderate interaction with the adsorbed H, facilitating superior HER catalysis. Our findings showcase a new paradigm of cluster engineering for modulating GDY's reactivity that holds great promise as a universal approach for the design of high-performance GDY-based electrocatalysts beyond HER.

Remodeling the Electronic Structure of Metallic Nickel and Ruthenium via Alloying in a Molecular Template for Sustainable Hydrogen Evolution.

The reasonably constructed high-performance electrocatalyst is crucial to achieve sustainable electrocatalytic water splitting. Alloying is a prospective approach to effectively boost the activity of metal electrocatalysts. However, it is a difficult subject for the controllable synthesis of small alloying nanostructures with high dispersion and robustness, preventing further application of alloy catalysts. Herein, we propose a well-defined molecular template to fabricate a highly dispersed NiRu alloy with ultrasmall size. The catalyst presents superior alkaline hydrogen evolution reaction (HER) performance featuring an overpotential as low as 20.6 ± 0.9 mV at 10 mA·cm-2. Particularly, it can work steadily for long periods of time at industrial-grade current densities of 0.5 and 1.0 A·cm-2 merely demanding low overpotentials of 65.7 ± 2.1 and 127.3 ± 4.3 mV, respectively. Spectral experiments and theoretical calculations revealed that alloying can change the d-band center of both Ni and Ru by remodeling the electron distribution and then optimizing the adsorption of intermediates to decrease the water dissociation energy barrier. Our research not only demonstrates the tremendous potential of molecular templates in architecting highly active ultrafine nanoalloy but also deepens the understanding of water electrolysis mechanism on alloy catalysts.

Interfacial engineering of high-performance Fe2P2O7-based electrocatalysts for alkaline exchange membrane fuel cells

Fuel cells promise high energy density and energy conversion efficiency but are plagued by the scarcity of platinum for facilitating the oxygen reduction reaction (ORR). Herein, a facile synthesis of a heterojunction electrocatalyst of ZIF-8 derived carbon (Z8C) supported Fe2P2O7 (Fe2P2O7@Z8C) is reported. The electrocatalyst exhibited higher half-wave potential than the state-of-the-art Pt/C catalyst by more than 33 mV and achieved a peak power density of 152.47 mW cm−2, outperforming the Pt/C-driven cell by ca. 14.5 mW cm−2 in alkaline membrane electrode assemblies under similar operating conditions. X-ray photoelectron and X-ray absorption spectroscopic studies suggested a spontaneous electron redistribution across the heterojunction interface in Fe2P2O7@Z8C. Density functional theory calculations indicated that the electron redistribution may remarkably promote the intrinsic activity of Fe2P2O7@Z8C toward the four-electron ORR pathway. These findings offer an indispensable strategy for rational design of highly efficient and durable non-noble electrocatalysts.

Valorising lignocellulosic biomass to high-performance electrocatalysts via anaerobic digestion pretreatment

AbstractAnaerobic digestion (AD) was initially evaluated as a potential preprocessing method for preparing biomass-based carbon electrocatalysts in this study. The AD pretreatment succeeded in the structural depolymerization and nitrogen enrichment of Hybrid Pennisetum, which provided favorable conditions to achieve efficient and homogeneous nitrogen introduction due to microorganism community enrichment and provided a porous structure by degradation of the biodegradable components. The resulted biochar exhibited improved physiochemical properties including higher specific surface areas, nitrogen content and graphitization degree than that obtained from pyrolyzing raw biomass. These improvements were positively correlated with the AD time and showed to have enhanced the performance in oxygen reduction reaction and practical microbial fuel cell applications. Amongst the investigated samples, the obtained biochar pretreated by AD for 15 days exhibited the most excellent performance with an onset potential of 0.17 V (VS. saturated calomel electrode) and the maximal power density of 543.2 mW cm−2 assembled in microbial fuel cells. This study suggested applying AD as a new biological pretreatment in the preparation of biomass-based electrocatalysts, and provided a unique pathway for fabricating high-performance biochar-based catalysts by structure optimization and N-containing active sites construction via gentle biological method, thereby providing a cost-effective method to fabricate metal-free catalysts for oxygen reduction reaction. Graphical Abstract

In situ construction of a P-doped TiO2/Ti3C2Tx heterostructure with local site optimization to improve Li-O2 battery performance

The performance of Li-O2 batteries is seriously limited by the sluggish kinetics of the mass transition in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). To explore a useful strategy to overcome these limitations, herein, we constructed a P-doped TiO2/Ti3C2Tx heterostructure (PTT) with local active site optimization, in which the highly conductive substrate anchored the P-TiO2 nanoparticles with a selective adsorption and conversion of LiOx. In contrast to the TiO2/Ti3C2Tx heterostructure with a relatively uniform active site inducing typical toroidal Li2O2, the introduction of P-doping generates a unique nanosheet array Li2O2 on the PTT surface as a discharge product. This unique structure is endowed with a shorter Li+ diffusion path and benefits mass transfer in ORR and OER, facilitating the reaction kinetics. It presents obviously enhanced battery performance with a high specific capacity of 13,482 mAh g−1 and decreased discharge–charge overpotential, as well as superior cycling stability of 190 cycles. Furthermore, this novel and efficient electrocatalyst can stably operate for more than 650 cycles at 1000 mA g−1 with the addition of a LiI redox mediator. This study provides new insight into high-performance electrocatalyst design in Li2O2 related battery system.

Modulating Electronic Structure of Iridium Single-Atom Anchored on 3D Fe-Doped β-Ni(OH)2 Catalyst with Nanopyramid Array Structure for Enhanced Oxygen Evolution Reaction.

Developing high-performance electrocatalysts for oxygen evolution reaction (OER) is crucial in the pursuit of clean and sustainable hydrogen energy, yet still challenging. Herein, a spontaneous redox strategy is reported to achieve iridium single-atoms anchored on hierarchical nanosheet-based porous Fe doped β-Ni(OH)2 pyramid array electrodes (SAs Ir/Fe-β-Ni(OH)2 ), which exhibits high OER performance with a low overpotential of 175mV at 10mAcm-2 and a remarkable OER current density in alkaline electrolyte, surpassing Fe-β-Ni(OH)2 /NF and IrO2 by 31 and 38 times at 1.43V versus RHE, respectively. OER catalytic mechanism demonstrates that the conversion of * OH→* O and the active lattice O content can be significantly improved due to the modulation effect of the Ir single atoms on the local electronic structure and the redox behavior of FeNi (oxy) hydroxide true active species. This work provides a promising insight into understanding the OER enhancement mechanism for Ir single-atoms modified FeNi-hydroxide systems.

Hierarchical PtCuMnP Nanoalloy for Efficient Hydrogen Evolution and Methanol Oxidation.

The higher amount of Pt usage and its poisoning in methanol oxidation reaction in acidic media is a major setback for methanol fuel cells. Herein, a promising dual application high-performance electrocatalyst has been developed for hydrogen evolution and methanol oxidation. A low Pt-content nanoalloy co-doped with Cu, Mn, and P is synthesized using a modified solvothermal process. Initially, ultrasmall ≈2.9 nm PtCuMnP nanoalloy is prepared on N-doped graphene-oxide support and subsequently, it is characterized using several analytical techniques and examined through electrochemical tests. Electrochemical results show that PtCuMnP/N-rGO has a low overpotential of 6.5 mV at 10 mA cm-2 in 0.3m H2 SO4 and high mass activity for the hydrogen evolution reaction. For the methanol oxidation reaction, the PtCuMnP/N-rGO electrocatalyst exhibits robust performance. The mass activity of PtCuMnP/N-rGO is 6.790mA mg-1 Pt , which is 7.43 times higher than that of commercial Pt/C (20% Pt). Moreover, in the chronoamperometry test, PtCuMnP/N-rGO shows exceptionally good stability and retains 72% of the initial current density even after 20,000 cycles. Furthermore, the PtCuMnP/N-rGO electrocatalyst exhibits outstanding performance for hydrogen evolution and methanol oxidation along with excellent anti-poisoning ability. Hence, the developed bifunctional electrocatalyst can be used efficiently for hydrogen evolution and methanol oxidation.

Carbon Dioxide and Nitrate Electrocatalytic C-N Coupling for Sustainable Production of Urea

Review Carbon Dioxide and Nitrate Electrocatalytic C-N Coupling for Sustainable Production of Urea Litao Jia, and Fanghua Li * School of Environment, Harbin Institute of Technology, Harbin 150090, China * Correspondence: fanghuahope01@hit.edu.cn Received: 15 December 2023; Revised: 17 January 2024; Accepted: 19 February 2024; Published: 5 March 2024 Abstract: The electrocatalytic co-reduction of carbon dioxide (CO2) and nitrate (NO3−) for urea synthesis under environmental conditions offers a promising solution for achieving sustainable environmental management. Besides, electrochemical urea synthesis is an alternative approach for cleaner production of urea compared to the conventional urea industrial production process with high energy consumption and pollution. However, lower urea yield, lower selectivity and unclear C-N coupling reaction mechanism are still the main challenges to its large-scale application. In this review, we focus on accurate and reliable detection methods and evaluation criteria for urea products, recent progress on CO2 and NO3− electrocatalytic co-reduction synthesis of urea, rational design of high-performance electrocatalysts, and C-N coupling reaction mechanism of urea electrochemical synthesis under atmospheric conditions. This review could contribute to the development of electrochemical urea synthesis via effective remediation of CO2 and NO3−.

Molecular architectures of iron complexes for oxygen reduction catalysis—Activity enhancement by hydroxide ions coupling

Developing cost-effective and high-performance electrocatalysts for oxygen reduction reaction (ORR) is critical for clean energy generation. Here, we propose an approach to the synthesis of iron phthalocyanine nanotubes (FePc NTs) as a highly active and selective electrocatalyst for ORR. The performance is significantly superior to FePc in randomly aggregated and molecularly dispersed states, as well as the commercial Pt/C catalyst. When FePc NTs are anchored on graphene, the resulting architecture shifts the ORR potentials above the redox potentials of Fe2+/3+ sites. This does not obey the redox-mediated mechanism operative on conventional FePc with a Fe2+-N moiety serving as the active sites. Pourbaix analysis shows that the redox of Fe2+/3+ sites couples with HO- ions transfer, forming a HO-Fe3+-N moiety serving as the ORR active sites under the turnover condition. The chemisorption of ORR intermediates is appropriately weakened on the HO-Fe3+-N moiety compared to the Fe2+-N state and thus is intrinsically more ORR active.

Ru Regulated Electronic Structure of Pdx Cuy Nanosheets for Efficient Hydrogen Evolution Reaction in Wide pH Range.

The development of highly effective catalysts for hydrogen evolution reaction (HER) in a wide pH range is crucial for the sustainable utilization of green energy utilization, while the slow kinetic reaction rate severely hinders the progress of HER. Herein, the reaction kinetic issue is solved by adjusting the electronic structure of the Ru/Pdx Cuy catalysts. The champion catalyst displays a remarkable performance for HER with the ultralow overpotential (27, 28, and 97mV) in 1.0m KOH, 0.5m H2 SO4 , and 1.0m PBS at 10mA cm-2 and high the mass activity (3036 A g-1 ), respectively, superior to those of commercial Pt/C benchmarks and most of reported electrocatalysts, mainly due to its low reaction activation energy. Density functional theory (DFT) calculations indicate that Ru doping contributes an electron-deficient 3d band, which promotes water adsorption. Additionally, this also leads to an upward shift of the d-band center of Pd and a downward shift of the d-band center of Cu, further optimizing the adsorption/dissociation of H2 O and H* . Results from this work may provide an insight into the design and synthesis of high-performance pH-universal HER electrocatalysts.

In-situ construction of cation vacancies in amphoteric-metallic element-doped NiFe-LDH as ultrastable and efficient alkaline hydrogen evolution electrocatalysts at 1000 mA cm−2

Developing efficient and stable electrocatalysts at affordable costs is very important for large-scale production of green hydrogen. In this study, unique amphoteric metallic element-doped NiFe-LDH nanosheet arrays (NiFeCd-LDH, NiFeZn-LDH and NiFeAl-LDH) using as high-performance bifunctional electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) were reported, by tuning electronic structure and vacancy engineering. It was found that NiFeCd-LDH possesses the lowest overpotentials of 85 mV and 240 mV (at 10 mA cm−2) for HER and OER, respectively. Density functional theory (DFT) calculations reveal the synergistic effect of Cd vacancies and Cd doping on improving alkaline HER performance, which promote the achievement of excellent catalytic activity and ultrastable hydrogen production at a large current density of 1000 mA cm−2 within 250 h. Besides, the overall water splitting performance of the as-prepared NiFeCd-LDH requires only 1.580 V to achieve a current density of 10 mA cm−2 in alkaline seawater media, underscoring the importance of modifying the electronic properties of LDH for efficient overall water splitting in both alkaline water/seawater environments.

Boron-alloyed porous network platinum nanospheres for efficient oxygen reduction in proton exchange membrane fuel cells

Alloying (or doping) non-metals with platinum (Pt) is an advanced solution for the development of high-performance Pt-based electrocatalysts for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). Herein, we report boron (B)-alloyed Pt nanospheres (B-PtNSs) with a porous network nanostructure by a combination strategy of confinement reduction and post-boronation. B-alloying can induce effective electronic/geometric structures, strong Pt-B coordination, and lowered d-band center to weaken the binding energy of oxygenated intermediates on the Pt surface. The H2-O2 PEMFC with such a B-PtNSs/C as the cathode catalyst can reach a maximum power density of 1.49 W cm−2, about 1.28 times higher than that of Pt/C. After 30,000 voltage cycles in the range of 0.6 ∼ 0.95 V, only a 14.1 % loss of initial peak power density can be observed, while that with Pt/C declines 45.7 %. Non-metals alloying with Pt-based nanostructures can enable high-performance ORR electrocatalysts for their practical application in PEMFCs.

Nitrogen-doped carbon layer encapsulating NiFeP nanosheet arrays as high-performance electrocatalyst for oxygen evolution reaction

With water electrolysis restricted to the slow kinetics of oxygen evolution reaction (OER), developing catalysts with both high activity and durability has become an urgent requirement for the development of current water electrolysis technology. Herein, we successfully prepared nitrogen-doped carbon layer encapsulating NiFe phosphide nanosheet arrays (denoted as N-C@NiFeP) catalysts by using a simple hydrothermal method combined with low temperature plasma technique. Phosphating conversion, carbonization, and nitrogen doping were realized by the same high-efficiency plasma treatment process. The nitrogen-doped carbon-coated structure modifies the NiFeP electronic structure, resulting in remarkable OER performances of N-C@NiFeP nanosheet arrays. The N-C@NiFeP nanosheet arrays possessed a tiny Tafel slope value of 27 mV dec−1 and a low overpotential of 229 mV at 10 mA cm−2. Meanwhile, the N-C@NiFeP nanosheet arrays also exhibited impressive long-term durability of 100 h under sequential OER testing at 100 mA cm−2. Our work was instrumental in paving new pathways for the construction of efficient and stable OER electrocatalysts.

Sulfate anchored on the defective NiO by ion irradiation realizes enhanced oxygen evolution reaction

NiO has attracted wide attention in the past decade as a cost-effective electrochemical catalyst for OER. However, its relatively poor performance and conductivity limit its commercial applications. Here, we highlight a unique ion irradiation method to enhance the catalytic activity of NiO. Benefiting from sulfate anchoring and the introduction of oxygen vacancies by He+ ion irradiation, the optimal catalyst (ir-S-NiO) exhibits an outstanding OER performance with a low overpotential of 269 mV at 10 mA cm−2. Moreover, the fabricated Anion exchange membrane water electrolyzer (AEMWE) constructed by the ir-S-NiO is demonstrated to need a cell voltage of 1.72 V to reach a current density of 0.1 A cm−2 and shows remarkably long-term stability for 200 h without obvious attenuation at the current density of 0.5 A cm−2. This work provides a new method for the development of high-performance and stable OER electrocatalysts.

High-Performance Iridium-Molybdenum Oxide Electrocatalysts for Water Oxidation in Acid: Bayesian Optimization Discovery and Experimental Testing.

Ir oxides are costly and scarce catalysts for oxygen evolution reaction (OER) in acid. There has been extensive interest in developing alternatives that are either Ir-free or require smaller amounts of Ir to drive the reactions at acceptable rates. One design strategy is to identify Ir-based mixed oxides that achieve similar performance while requiring smaller amounts of Ir. The obstacle to this strategy has been a very large phase space of the Ir-based mixed metal oxides, in terms of the metals combined with Ir and the different crystallographic structures of the mixed oxides, which prevents a thorough exploration of possible materials. In this work, we developed a workflow that uses machine-learning-aided Bayesian optimization in combination with density functional theory to make the exploration of this phase space plausible. This screening identified Mo as a promising dopant for forming acid-tolerant Ir-based oxides for the OER. We synthesized and characterized the Ir-Mo mixed oxides in the form of thin-film electrocatalysts with a known surface area. We show that these mixed oxides exhibited overpotentials ∼30 mV lower than a pure Ir control while maintaining 24% lower Ir dissolution rates than the Ir control. These findings suggest that Mo is a promising dopant and highlight the promise of machine learning to guide the experimental exploration and optimization of catalytic materials.

Hierarchical Porous Nonprecious High-entropy Alloys for Ultralow Overpotential in Hydrogen Evolution Reaction.

Water electrolysis is considered the cleanest method for hydrogen production. However, the widespread popularization of water splitting is limited by the high cost and scarce resources of efficient platinum group metals. Hence, it is imperative to develop an economical and high-performance electrocatalyst to improve the efficiency of hydrogen evolution reaction (HER). In this study, a hierarchical porous sandwich structure is fabricated through dealloying FeCoNiCuAl2 Mn high-entropy alloy (HEA). This free-standing electrocatalyst shows outstanding HER performance with a very small overpotential of 9.7mV at 10 mA cm-2 and a low Tafel slope of 56.9 mV dec-1 in 1 M KOH solution, outperforming commercial Pt/C. Furthermore, this electrocatalytic system recorded excellent reaction stability over 100 h with a constant current density of 100 mA cm-2 . The enhanced electrochemical activity in high-entropy alloys results from the cocktail effect, which is detected by density functional theory (DFT) calculation. Additionally, micron- and nano-sized pores formed during etching boost mass transfer, ensuring sustained electrocatalyst performance even at high current densities. This work provides a new insight for development in the commercial electrocatalysts for watersplitting.

Self-supported ultrathin NiMn-LDH nanosheets for highly active and robust urea oxidation

Due to its low equilibrium potential, urea oxidation reaction (UOR) is an advantageous alternative to the conventional anodic water oxidation reaction (OER) for energy-saving hydrogen production. Developing energy- and time-saving methods to synthesize active and stable UOR catalysts is significant. Herein, we present a simple and time-efficient method for the direct growth of defect-rich few-layered NiMn-layered double hydroxide (NiMn-LDH) nanosheets on nickel foam at ambient temperature and pressure. The defect-rich, few-layered structure exposes numerous active sites, promoting the formation of high-oxidation state Ni species at low overpotentials. Additionally, the introduction of Mn facilitates Ni oxidation and stabilizes in-situ formed NiOOH species. The optimized f-NiMn-LDH catalyst exhibits compelling UOR activity, requiring only 1.310/1.330/1.387 V for 10/100/400 mA cm−2 UOR, respectively. When used directly in urea-assisted hydrogen production, it achieves a low cell voltage of 1.436 V for a high current density of 100 mA cm−2, representing a substantial 249 mV reduction compared to water electrolysis. This work offers a simple strategy for preparing high-performance electrocatalysts for energy-efficient hydrogen production via urea-assisted water splitting.

Tip and heterogeneous effects co-contribute to a boosted performance and stability in zinc air battery

The zinc-air battery (ZAB) performance and stability strongly depend on the structure of bifunctional electrocatalyst for oxygen reduction/evolution reaction (ORR/OER). In this work, we combine the tip and heterogeneous effects to construct cobalt/cobalt oxide heterostructure nanoarrays (Co/CoO-NAs). Due to the formed heterostructure, more oxygen vacancies are found for Co/CoO-NAs resulting in a 1.4-fold higher ORR intrinsic activity than commercial carbon supported platinum electrocatalyst (Pt/C) at 0.8 V versus reversible hydrogen electrode (vs. RHE). Moreover, a fast surface reconstruction is observed for Co/CoO-NAs during OER catalysis evidenced by in-situ electrochemical impedance spectroscopy and Raman tests. In addition, the tip effect efficiently lowers the mass transfer resistance triggering a low overpotential of 347 mV at 200 mA cm−2 for Co/CoO-NAs. The strong electronic interplay between cobalt (Co) and cobalt oxide (CoO) contributes to a stable battery performance during 1200 h galvanostatic charge–discharge test at 5 mA cm−2. This work offers a new avenue to construct high-performance and stable oxygen electrocatalyst for rechargeable ZAB.

Three-dimensional heterostructured MnNiCoP/FeOOH cross-linked nano-flake supported by Ni Foam as a bifunctional electrocatalysts for overall water splitting

The production of three-dimensional heterogeneous structures is a vital approach for the creation of high-performance bifunctional electrocatalysts. Herein, three-dimensional heterostructure MnNiCoP/FeOOH (MNC-P/FeOOH) supported by Ni foam was prepared by simple electrodeposition and phosphorylation as a bifunctional electrocatalyst. The results showed that the required overpotential for MNC-P/FeOOH catalyst to reach 100 mA cm−2 current density was 124 mV and 251 mV in 1.0 M KOH solution, respectively. Construction of heterojunction not only improves the OER performance of MnNiCoP, but also reduces the potential required to drive the integral water splitting at 100 mA cm−2 current density. The electrocatalytic activity of MNC-P/FeOOH is greatly increased due to a distinctive interface synergy and strong electronic contacts in the MNC-P/FeOOH heterojunction. This design approach of bifunctional transition metal phosphides provides a potential route to achieve total water splitting.

Co3O4/WO3/C Nanorods with Porous Structures as High-Performance Electrocatalysts for Water Splitting

Co₃O₄/WO₃/C Nanorods with Porous Structures as High-Performance Electrocatalysts for Water Splitting