SnO2@PdAg Core-Shell Nanoarchitecture Promotes Active and Stable Alcohol Electrooxidations.

Developing efficient Pd-based electrocatalysts is of vital importance for the application of direct alcohol fuel cells. Designing the core-shell architecture of Pd-based nanomaterials rationally has emerged as an effective strategy to promote the sluggish kinetics of anodic reactions. Herein, the PdAg alloy is reduced on a non-noble metal oxide surface for the formation of a core-shell nanostructure. The optimized SnO2@PdAgh nanospheres deliver the optimal catalytic performance compared with other counterparts and commercial Pd/C. The structural investigation reveals that the introduction of Ag and formation of a PdAg/SnO2 heterointerface effectively regulate the electronic structure of Pd, making SnO2@PdAgh a highly active catalyst for methanol and ethylene glycol oxidation reactions. Impressively, the strong interaction between the PdAg shell and SnO2 core stabilizes the metal-oxide heterointerface, contributing to the improved stability of SnO2@PdAgh in electrocatalytic reactions. This study proposes the use of non-noble metal oxides as the core to suppress the dissolution of the catalysts and highlights the rational design of core@shell nanoarchitectures.

Solvothermal synthesis of PdCu nanorings with high catalytic performance for alcohol electrooxidation.

Two-dimensional (2D) Pd-based nanostructures with a high active surface area and a large number of active sites are commonly used in alcohol oxidation research, whereas the less explored ring structure made of nanosheets with large pores is of interest. In this study, we detail the fabrication of PdCu nanorings (NRs) featuring hollow interiors and low coordinated sites using a straightforward solvothermal approach. Due to increased exposure of active sites and the synergistic effects of bimetallics, the PdCu NRs exhibited superior catalytic performance in both the ethanol oxidation reaction (EOR) and the ethylene glycol oxidation reaction (EGOR). The mass activities of PdCu NRs for EOR and EGOR were measured at 7.05 A/mg and 8.12 A/mg, respectively, surpassing those of commercial Pd/C. Furthermore, the PdCu NRs demonstrated enhanced catalytic stability, maintaining higher mass activity levels compared to other catalysts during stability testing. This research offers valuable insights for the development of efficient catalysts for alcohol oxidation.

Synthesis of Pt-doped CoFe layered double hydroxide derived from zeolitic imidazolate framework for efficient electrochemical oxygen evolution reaction.

Zeolitic imidazolate frameworks (ZIFs), a class of promising metal organic frameworks (MOFs) material, display high porosity and chemical/thermal stability. However, there are problems such as few active sites and restricted exposed active areas, which limit the oxygen evolution reaction (OER) performance of catalysts. Here, starting from zeolitic imidazolate framework-67 (ZIF-67), we have successfully synthesized Pt-doped CoFe layered double hydroxide (Pt/CoFe LDH) catalysts for efficient OER catalysis. The obtained Pt/CoFe LDH-4 catalysts provides large surface areas and abundant active sites, which further improves the OER performance. In detail, the Pt/CoFe LDH-4 exhibits a lower overpotential of 263 mV at a current density of 40 mA cm-2, in 1 M KOH solution, the stability of the catalyst exceeds 120 h at this current density, far superior to commercial catalyst RuO2. This study describes a new design idea for synthesis of LDH catalytic materials with low noble metal doping, which broadens the way to the synthesis of robust OER catalysts derived from ZIF-67.

Ir-Doped Core-Shell Hollow Heterogeneous Nanospindles for Electrocatalytic Oxygen Evolution Reaction.

By utilizing Metal-organic framework (MOF) materials as a base, constructing electrocatalysts with heterogeneous structures offers advantages for catalyzing water splitting. In this study, a hollow heterogeneous nanocatalyst, Ir-MIL-88A@NiFe-LDHs, was prepared by growing a layered double hydroxides (LDHs) shell on MIL-88A substrate. The catalyst shows excellent oxygen evolution reaction (OER) performance in a 1.0 M KOH solution, requiring only 217 mV overpotential to achieve a current density of 10 mA cm-2 with a Tafel slope of 62.18 mV dec-1, indicating significant electrocatalytic performance and reaction kinetics characteristics. Furthermore, long-term OER testing also demonstrates the catalyst's outstanding stability. Emphasizing the interfacial interaction between MOF and LDHs, as well as the synergistic effect among Ni, Fe, and Ir elements, the study highlights how these factors collaboratively control the local electronic structure of the hollow Ir-MIL-88A@NiFe-LDHs, resulting in an efficient MOF-derived electrocatalyst.

2D petal-like PdAg nanosheets promote efficient electrocatalytic oxidation of ethanol and methanol.

The development of efficient alcohol electrooxidation catalysts is of vital importance for the commercialization of direct liquid fuel cells. As emerging advanced catalysts, two-dimensional (2D) noble metal nanomaterials have attracted much research attention due to their intrinsic structural advantages. Herein, we report the synthesis of petal-like PdAg nanosheets (NSs) with an ultrathin 2D structure and jagged edges via a facile wet-chemical approach, combining doping engineering and morphology tuning. Notably, the highly active sites and Pd-Ag composition endowed PdAg NSs with improved toxicity tolerance and substantially improved the durability toward the ethanol/methanol oxidation reaction (EOR/MOR). Moreover, the electronic effect and synergistic effect significantly enhanced the EOR and MOR activities in comparison with Pd NSs and commercial Pd/C. This work provides efficient catalysts for fuel electrooxidations and deep insight into the rational design and fabrication of novel 2D nanoarchitecture.

Insights into the formation and growth of high entropy PdPtSnPbNi nanowires to obtain catalysts with high alcohol electrocatalytic oxidation activity.

High-entropy alloys have raised great interest in recent years because of their potential applications for multi-electron reactions owing to their diverse active sites and multielement tunability. However, the difficulty of synthesis is an obstacle to their development due to phase separation often exists. In addition, it's a challenge to precisely control morphology in harsh conditions, thus leading to nanoparticles in many cases. We report a facile method to obtain PdPtPbSnNi HEA NWs by solvothermal synthesis method that no existing phase separation. PdPb nucleation plays a role in the formation of the high-entropy structure that serves as a PdPb nucleus for Sn, Ni, and Pt reduction subsequently, thus forming a single phase and an orderly-arranged nanowire structure. Significantly, the optimized PdPtPbSnNi NWs exhibit excellent catalytic activity and stability for both EOR and MOR which is 4.36 A mgPd+Pt-1 and 4.34 A mgPd+Pt-1, respectively. This study highlights a novel strategy for morphology tuning, providing a prospect for designing superior high-entropy nano-catalysts for multi-step reactions.

Synthesis of Solvent-Mediated Morphology-Controlled PdSn Alloy Nanocatalysts and their Application in Electrocatalysis of Ethylene Glycol and Ethanol.

2D nanodendrites (NDs) and nanosheets (NSs) have been regarded as efficient nanocatalysts for enhancing the electrocatalytic performance due to their low coordinated sites and abundant electrocatalytic centers. Nevertheless, it remains challenging to construct advanced NDs and NSs in a single reaction system. Herein, by tuning the volume ratios of mixed solvents, the reduction and diffusion rate of Sn2+ on Pd NSs template was rationally controlled to prepare PdSn NDs and PdSn NSs. Ascribed to the open 2D nanostructure, high specific surface area, and robust synergistic effect, the as-prepared PdSn NDs and PdSn NSs exhibited distinguished electrocatalytic activities for ethylene glycol oxidation reaction (EGOR) and ethanol oxidation reaction (EOR), as well as commendable electrocatalytic durability, which were far superior to the Pd NSs and commercial Pd/C. In addition, the PdSn NDs exhibited enhanced reaction kinetics because the characteristic branch structure exposed a high density of active sites. This work may provide significant guidance for preparing excellent nanocatalysts with various morphological features by simply optimizing the content of the coexisting solvents.

In Situ Electrodeposition of Ultralow Pt into NiFe-Metal-Organic Framework/Nickel Foam Nanosheet Arrays as a Bifunctional Catalyst for Overall Water Splitting.

Exploring highly effective bifunctional electrocatalysts with surface structural advantages and synergistic optimization effects among multimetals is greatly important for overall water splitting. Herein, we successfully synthesized Pt-loaded NiFe-metal-organic framework nanosheet arrays grown on nickel foam (Pt-NiFe-MOF/NF) via a facile hydrothermal-electrodeposition process. Benefiting from large exposed specific surface, optimal electrical conductivity and efficient metal-support interaction endow Pt-NiFe-MOF/NF with highly catalytic performance, exhibiting small overpotential of 261 mV toward oxygen evolution reaction and 125 mV toward hydrogen evolution reaction at a current density of 100 mA cm-2 in alkaline medium. More significantly, the assembled water electrolyzer comprising the Pt-NiFe-MOF/NF//Pt-NiFe-MOF/NF couple demands a low cell voltage of 1.45 V to reach 10 mA cm-2. This work renders a viable approach to design dual-functional electrocatalysts with exceptional electrocatalytic activity and stability at high current density, showing the great prospect of water electrolysis for commercial application.

Recent progress of Ni-based nanomaterials for the electrocatalytic oxygen evolution reaction at large current density.

The precise design and development of high-performing oxygen evolution reaction (OER) for the production of industrial hydrogen gas through water electrolysis has been a widely studied topic. A profound understanding of the nature of electrocatalytic processes reveals that Ni-based catalysts are highly active toward OER that can stably operate at a high current density for a long period of time. Given the current gap between research and applications in industrial water electrolysis, we have completed a systematic review by constructively discussing the recent progress of Ni-based catalysts for electrocatalytic OER at a large current density, with special focus on the morphology and composition regulation of Ni-based electrocatalysts for achieving extraordinary OER performance. This review will facilitate future research toward rationally designing next-generation OER electrocatalysts that can meet industrial demands, thereby promoting new sustainable solutions for energy shortage and environment issues.

Ir-Doped Bilayer Heterojunction Hollow Nanoboxes for Electrocatalytic Oxygen Evolution.

The fabrication of hollow nanoelectrocatalysts with multilayered heterogeneous interfaces, derived from metal-organic framework (MOF) materials, represents a highly efficient strategy that promotes the oxygen evolution reaction (OER). Within this research, we successfully synthesized a hollow nanobox of Ir-doped ZIF-67@CoFe PBA with bilayer heterointerfaces. The distinctive structure of Ir-ZIF-67@CoFe PBA provides a substantial number of active sites for reaction intermediates, resulting in improved utilization of precious metals. Furthermore, experimental results indicate the outstanding electrocatalytic performance of the optimized Ir-ZIF-67@CoFe PBA, as indicated by a mere 269 mV overpotential at 10 mA·cm-2, accompanied by a small Tafel slope of 80.1 mV·dec-1. Moreover, the Schottky junction formed between the heterojunction and Ir within Ir-ZIF-67@CoFe PBA accelerates the electron-transfer rate, contributing to its exceptional catalytic performance compared to that of a catalyst derived solely from ZIF-67. This distinctive feature of the catalyst holds tremendous application value.

Rapid synthesis of Palladium-Platinum-Nickel ultrathin porous nanosheets with high catalytic performance for alcohol electrooxidation.

Bimetallic two-dimensional (2D) nanomaterials are widely used in electrocatalysis owing to their unique physicochemical properties, while trimetallic 2D materials of porous structures with large surface area are rarely reported. In this paper, a one-pot hydrothermal synthesis of ternary ultra-thin PdPtNi nanosheets is developed. By adjusting the volume ratio of the mixed solvents, PdPtNi with porous nanosheets (PNSs) and ultrathin nanosheets (UNSs) was prepared. The growth mechanism of PNSs was investigated through a series of control experiments. Notably, thanks to the high atom utilization efficiency and fast electron transfer, the PdPtNi PNSs have remarkable activity of methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR). The mass activities of the well-tuned PdPtNi PNSs for MOR and EOR were 6.21 A mg-1 and 5.12 A mg-1, respectively, much higher than those of commercial Pt/C and Pd/C. In addition, after durability test, the PdPtNi PNSs exhibited desirable stability with the highest retained current density. Therefore, this work provides a significant guidance for designing and synthesizing a new 2D material with excellent catalytic performance toward direct fuel cells applications.

One-pot synthesis of 3D surface-wrinkled PdAu nanospheres for robust alcohols electrocatalysis.

Three dimensional (3D) noble-metal nanomaterials with special surface structures have been regarded as high-performance catalysts for alcohol oxidation on account of their superior thermal stability, electrical conductivity and large specific surface area. Although extensive efforts have been devoted to the preparation of 3D Pd-based catalysts with superior activity and stability, designing a simple, effective and eco-friendly method remains a challenge. Herein, we developed a facile one-step coreduction strategy to synthesize a series of 3D surface-wrinkled PdAu nanospheres (NSs) with tunable Pd/Au atomic ratios and found a universal method to prepare surface-wrinkled PdM (M = Au, Pt, Cu and Pb) NSs. Benefiting from the function of the surfactant cetyltrimethylammonium chloride (CTAC), the synthesized PdAu NSs with different composition possess abundant surface wrinkles, which is beneficial for exposing more electroactive centers. Attributed to the unique geometric morphology and optimized atomic ratio, the PdAu-2 NSs exhibited an optimal mass activity (MA) of 8103 mA mg-1 and 5113 mA mg-1 for the ethylene glycol oxidation reaction (EGOR) and ethanol oxidation reaction (EOR), which was 6.1 and 4.1 times that of commercial Pd/C, respectively. Moreover, the PdAu-2 NSs exhibited superb stability after long-term current-time (i-t) and cyclic voltammetry (CV) tests of the EGOR and EOR. This work not only provides new avenues to engineer PdAu NSs with enhanced electrocatalytic performance but also offers guidance for extending to more 3D PdM (M = other metals) NSs with novel morphology applied to fuel cell fields.

Activable Ru-PdRu nanosheets with heterogeneous interface for High-efficiency alcohol oxidation reaction.

Fabricating 2D nanomaterials with heterogeneous structure is a feasible way to improve catalytic performance owing to its large surface area and tunable electron structure. However, such a category has not been widely reported in the field of alcohol oxidation reaction (AOR). In this work, we reported a new type of heterostructure nanosheet with Ru nanoparticles decorated around the edge of PdRu nanosheets (Ru-PdRu HNSs). Particularly, strong electronic interaction and sufficient active sites attributed to the construction of heterogeneous interface, is the key to the superior electrocatalytic behavior of Ru-PdRu HNSs towards methanol oxidation reaction (MOR), ethylene glycol oxidation reaction (EGOR), and glycerol oxidation reaction (GOR). Remarkably, owing to the enhanced electron transfer brought by the introduction of the Ru-PdRu heterogeneous interface, these novel nanosheets are highly durable. Apart from being able to maintain the highest current density after 4000 s chronoamperometry test, Ru-PdRu HNSs can be reactivated with negligible activity loss in MOR and GOR test after four consecutive i-t experiments. Impressively, in the EGOR test, after reactivation, the current density is step-wisely increased, making it one of the best AOR electrocatalysts.

In situ phosphoselenization induced heterointerface engineering endow NiSe2/Ni2P/FeSe2 hollow nanocages with efficient water oxidation electrocatalysis performance.

Exploiting Earth-abundant and highly effective electrocatalysts toward the oxygen evolution reaction (OER) is critical for boosting water splitting efficiency. Herein, we proposed a novel in situ phosphoselenization strategy to fabricate heterostructured NiSe2/Ni2P/FeSe2 (NiFePSe) nanocages with a modified electronic structure and well-defined nanointerfaces. Owing to the strong interfacial coupling and synergistic effect among the three components, the prepared NiFePSe nanocages exhibit superior OER performance with an ultralow overpotential of 242 mV at 10 mA cm-2 and a small Tafel slope of 55.8 mV dec-1 along with robust stability in 1 M KOH. Remarkably, the highly open 3D porous architecture, delicate internal voids, and numerous surface defects endow the NiFePSe nanocages with abundant active sites and enhanced electron mobility. In addition, the super-hydrophilic surface is conducive to facilitating mass transfer between the electrolyte and electrode and rapidly releasing the bubbles. This work may lead to new breakthroughs in the tuning of multi-component transition metal catalysts and the designing of highly active and durable materials for water splitting.

Ce-Modified Flowerlike NiFe-MOF Nanostructure Based on Ion Competitive Coordination for Enhancing the Oxygen Evolution Reaction.

Metal-organic framework (MOF) has become a popular electrocatalyst for the oxygen evolution reaction (OER) because of its large specific surface area and adjustable porosity. Nevertheless, the electrochemical performance of MOFs has been greatly limited by poor intrinsic conductivity and catalytic activity. Herein, we report a Ce-doped nanoflower-like MOF material Ce@NiFe-MOF-5 via a facile ion competitive coordination effect and doping method. Benefiting from the nanoflower structure formed by the stacking of nanosheets, a large number of active sites can be exposed, which favors electron/mass transfer during water oxidation. The coordination substitution of Ce ions not only promoted an increase in the number of active sites on the surface of the nanosheets but also optimized the electronic structure of pristine NiFe-MOF. The well-designed Ce@NiFe-MOF-5 catalysts exhibited superior OER performance under basic conditions, which only required an overpotential of 258 mV at a current density of 10 mA cm-2 and a Tafel slope of 54.44 mV dec-1. Moreover, when Ce@NiFe-MOF-5 served as an anode and Pt/C as a cathode, the two-electrode system only needed 1.56 V to drive overall water splitting at 10 mA cm-2.

Heterostructure engineering and ultralow Pt-loaded multicomponent nanocage for efficient electrocatalytic oxygen evolution.

Developing highly efficient electrocatalysts based on appropriate heterojunction engineering and electronic structure modification for the oxygen evolution reaction (OER) has been extensively recognized as an effective approach to increase the efficiency of water splitting. Herein, ultralow Pt-loaded (1 %) NiCoFeP@NiCoFe-PBA hollow nanocages with well-defined heterointerfaces and modified electronic environment are successfully fabricated. As expected, the obtained Pt-NiCoFeP@NiCoFe-PBA exhibits outstanding performance with a low overpotential of 255 mV at 10 mA cm-2 and a small Tafel slope of 57.2 mV dec-1. More specifically, the highly open three-dimensional structure, exquisite interior voids and abundant surface defects endow Pt-NiCoFeP@NiCoFe-PBA nanocages with more electrochemical active sites. Meanwhile, experimental results and mechanism studies also reveal that the construction of heterogeneous interfaces as well as incorporation of noble metals could readily induce strong synergistic effects and significantly tailor electronic configurations to optimize the binding energy of the intermediates, thereby achieving prominent OER performance.

Photoelectrocatalytic oxidation of ethylene glycol on trimetallic PdAgCu nanospheres enhanced by surface plasmon resonance.

The notable surface plasmon resonance (SPR) effect of some metals has been applied to improve the efficiency of alcohol oxidation reactions, whereas the comprehensive investigation of Cu-assisted photoelectrocatalysis remains challenging. We herein successfully prepared trimetallic PdAgCu nanospheres (NSs) with abundant surface bulges for the advanced ethylene glycol oxidation reaction (EGOR) and compared them with bimetallic PdAg NSs to investigate the performance enhancement mechanism. Impressively, the as-optimized PdAgCu NSs exhibited superb mass activity and electrochemical stability. Moreover, under visible light illumination, the mass activity of PdAgCu NSs increased to 1.62 times compared to that in the dark, and in contrast, the mass activity of PdAg NSs only increased to 1.48 times that in the dark. A mechanistic study indicated that the incorporation of Cu not only strengthens the whole SPR effect of PdAgCu NSs but also further modifies the electronic structure of Pd. This work highlighted that the incorporation of Cu into PdAg NSs further enhanced the photoelectrocatalytic performance and increased noble metal atom utilization, which may provide guidance to fabricate novel and promising nanocatalysts in the field of photoelectrocatalysis.

One-pot synthesis of PdPtAg porous nanospheres with enhanced electrocatalytic activity toward polyalcohol electrooxidation.

Porous nanospheres (PNSs) have great development prospects in the electrocatalysis field because of their structural characteristics, such as a large specific surface area. However, it is still a challenge to find a simple and energy-saving method for the controllable synthesis of PNS nanocatalysts. In this paper, a one-pot CTAC-assisted strategy was developed for the successful formation of PdPtAg PNSs with high porosity at room temperature. Benefitting from the unique structures, optimized composition, acceleration of charge transfer and enhanced resistance to CO poisoning, the PdPtAg PNSs displayed considerably improved electrocatalytic performance with high mass activity and stability toward the ethylene glycol oxidation reaction (EGOR) and glycerol oxidation reaction (GOR). The EGOR and GOR mass activities of PdPtAg were 5.00 A mgmetal-1 and 3.06 A mgmetal-1, which are 6.22 and 1.91 times that of commercial Pd/C, respectively. This work is expected to offer a new path for improving catalytic performance by simple design and adjustment of morphology.

Self-Reconstruction of Fe-Doped Co-Metal-Organic Frameworks Boosted Electrocatalytic Performance for Oxygen Evolution Reaction.

Rational design of facile and low-cost efficient electrocatalysts for oxygen evolution reaction (OER) is crucial to solve the energy crisis. Benefiting from in situ self-reconstruction from metal-organic frameworks (MOFs) to (oxy)hydroxides in alkaline electrolytes, MOFs have become alternative OER catalysts. Thus, Fe-doped Co-MOF nanosheets (Co-MOF/Fe) were prepared and utilized straightforwardly as OER electrocatalysts. CoFe-layered bimetallic hydroxides (CoFe-LDHs) with abundant active sites are obtained from in situ conversion of Co-MOF/Fe after etching by the KOH electrolyte, which are generally actual active species. Meanwhile, the introduction of Fe ions will also produce a synergistic effect that greatly improves the electrocatalytic OER performance. The optimized catalyst (Co-MOF/Fe10) shows exceptional OER activity (η10 = 260 mV) and excellent durability over 50 h. The outstanding OER performance of Co-MOF/Fe10 can also be reflected in the two-electrode hydrolyzer (1.57 V at 10 mA cm-2). This study offers a pathway to probe the catalytic mechanism of MOFs and the rational construction of efficient MOF-derived catalysts.

Hierarchical Hollow CoWO4-Co(OH)2 Heterostructured Nanoboxes Enabling Efficient Water Oxidation Electrocatalysis.

Rational design and construction of well-defined hollow heterostructured nanomaterials assembled by ultrathin nanosheets overtakes crucial role in developing high-efficiency oxygen evolution reaction (OER) electrocatalysts. Herein, a reliable metal-organic framework-mediated and cation-exchange strategy to tune the geometric structure and multicomponent heterostructures has been proposed for the fabrication of hollow CoWO4-Co(OH)2 hierarchical nanoboxes assembled by rich ultrathin nanosheets. Benefiting from the hierarchical hollow nanostructure, the CoWO4-Co(OH)2 nanoboxes offer plenty of metal active centers available for reaction intermediates. Moreover, the well-defined nanointerfaces between CoWO4 and Co(OH)2 can function as the bridge for boosting the efficient electron transfer from CoWO4 to Co(OH)2. As a consequence, the optimized CoWO4-Co(OH)2 nanoboxes can exhibit outstanding electrocatalytic performance toward OER by delivering 10 mA cm-2 with a low overpotential of 280 mV and a small Tafel slope of 70.6 mV dec-1 as well as outstanding electrochemical stability. More importantly, this CoWO4-Co(OH)2 heterostructured nanocatalyst can couple with Pt/C to drive overall water splitting to achieve 10 mA cm-2 with a voltage of 1.57 V.