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The precise structural integration of single-atom and high-entropy-alloy features for energy electrocatalysis is highly appealing for energy conversion, yet remains a grand challenge. Herein, we report a class of single-atom Mo-tailored PdPtNiCuZn high-entropy-alloy nanosheets with dilute Pt-Pt ensembles and intrinsic tensile strain (Mo1-PdPtNiCuZn) as efficient electrocatalysts for enhancing the methanol oxidation reaction catalysis. The as-made Mo1-PdPtNiCuZn delivers an extraordinary mass activity of 24.55 A mgPt−1 and 11.62 A mgPd+Pt−1, along with impressive long-term durability. The planted oxophilic Mo single atoms as promoters modify the electronic structure of isolated Pt sites in the high-entropy-alloy host, suppressing the formation of CO adsorbates and steering the reaction towards the formate pathway. Meanwhile, Mo promoters and tensile strain synergistically optimize the adsorption behaviour of intermediates to achieve a more energetically favourable pathway and minimize the methanol oxidation reaction barrier. This work advances the design of atomically precise catalytic sites by creating a new paradigm of single atom-tailored high-entropy alloys, opening an encouraging pathway to the design of CO-tolerance electrocatalysts. Atomically precise modification of high-entropy alloys is highly appealing for electrocatalysis. Here, the authors design single-atom Mo-tailored high-entropy alloy nanosheets with dilute Pt-Pt ensembles and intrinsic tensile strain for promoting methanol electro-oxidation towards formate. [ABSTRACT FROM AUTHOR]

The multi-metallene with an ultrahigh surface area has great potential in precise tuning of surface heterogeneous d-electronic correlation by surface strain effect for the distinctive surface electronic structure, which is a brand new class of promising 2D electrocatalyst for sustainable energy device application. However, achieving such an atomically thin multi-metallene still presents a great challenge. Herein, we present a new synthetic method for an atomic-level palladium-iridium (PdIr) bimetallene with an average thickness of only ∼1.0 nm for achieving superior catalysis in the hydrogen evolution reaction (HER) and the formic acid oxidation reaction (FAOR). The curved PdIr bimetallene presents a top-ranked high electrochemical active area of 127.5 ± 10.8 m2 gPd+Ir−1 in the reported noble alloy materials, and exhibits a very low overpotential, ultrahigh activity and improved stability for HER and FAOR. DFT calculation reveals that the PdIr bimetallene herein has a unique lattice tangential strain, which can induce surface distortion while concurrently creating a variety of concave-convex featured micro-active regions formed by variously coordinated Pd sites agglomeration. Such a strong strain effect correlates the abnormal on-site active 4d10-t2g-orbital Coulomb correlation potential and directly elevates orbital-electronegativity exposure within these active regions, resulting in a preeminent barrier-free energetic path for significant enhancement of FAOR and HER catalytic performance. [ABSTRACT FROM AUTHOR]

Ultrathin nanosheet catalysts deliver great potential in catalyzing the oxygen reduction reaction (ORR), but encounter the ceiling of the surface atomic utilizations, thus presenting a challenge associated with further boosting catalytic activity. Herein, a kind of PdPtCu ultrathin nanorings with increased numbers of electrocatalytically active sites is reported, with the purpose of breaking the activity ceiling of conventional catalysts. The as‐made PdPtCu nanorings possess abundant high‐index facets at the edge of both the exterior and interior surfaces. An ultrahigh electrochemical active surface area of 92.2 m2 g–1PGM is achieved on this novel catalyst, much higher than that of the commercial Pt/C catalyst. The optimized Pd39Pt33Cu28/C shows a great enhanced ORR activity with a specific activity of 2.39 mA cm–2 and a mass activity of 1.97 A mg–1PGM at 0.9 V (versus RHE), as well as superior durability within 30 000 cycles. Density function theory calculations reveal that the high‐index facets and alloying Cu atoms can optimize the oxygen adsorption energy, explaining the enhanced ORR activity. Overcoming a key technical barrier in sub‐nanometer electrocatalysts, this work successfully introduces the hollow structures into the ultrathin nanosheets, heralding the exciting prospects of high‐performance ORR catalysts in fuel cells. [ABSTRACT FROM AUTHOR]

The hydrogen evolution reaction (HER) is a pivotal element of electrochemical water splitting which is able to produce clean hydrogen as an alternative to fossil fuel. Developing efficient Pt‐based electrocatalysts for the HER to work at all pHs is highly desirable, however, still a significant challenge, especially in alkaline conditions due to sluggish water dissociation and OHad transfer. Here, a new strategy for making a class of amorphous WOx‐surface decorated PtNi@Pt dendritic nanowires (WOx‐PtNi@Pt DNWs) to achieve highly efficient pH‐universal HER electrocatalysis is reported. The as‐made WOx‐PtNi@Pt DNWs display superior HER performance with the overpotentials of 24, 5, and 22 mV in 0.1 m KOH, 0.1 m HClO4, and 0.5 m phosphate‐buffered saline, respectively, at a current density of 10 mA cm−2. The mass activity of WOx‐PtNi@Pt DNWs in alkaline conditions is 3.3 mA μgPt−1 at an overpotential of 70 mV, among the best in all the reported materials. Theoretical calculations confirm the introduction of WOx to the PtNi DNWs plays a pivotal role in promoting the efficient electron transfer for the alkaline and acidic HER. The activation of the PtNi region within the PtNiWO interface is achieved by the WOx induced strain effect, which guarantees the superior performance in the HER. [ABSTRACT FROM AUTHOR]

Hydrogen production through proton exchange membrane water electrolyzers (PEMWE) requires more active and stable electrocatalysts in acidic media. Herein, a class of Ir‐based alloys is reported with flower‐like structure as excellent electrocatalysts both for hydrogen and oxygen generation in acid. Specially, the IrNi alloy nanoflowers (IrNi NFs) present the best hydrogen evolution reaction (HER) performance, revealed by a low Tafel slope and overpotential at current density of 10 mA cm−2, exceeding the commercial Pt/C. It is discovered that alloying Ir with Ni can decrease the hydrogen binding energy (HBE) of Ir metal, resulting in almost 2.5 times increase in the HER intrinsic activity of IrNi NFs than Ir NFs. The IrNi NFs catalyst is also highly efficient in oxygen evolution reaction with mass activity of 379 A g−1 Ir at 1.51 V versus reversible hydrogen electrode. Furthermore, the overall water‐splitting devices using the IrNi NFs as catalysts for both cathode and anode show a low cell voltage of 1.60 V at 10 mA cm−2 and long‐term stability within 1000 cycles. This work uncovers that HBE optimization is the key of enhancing HER activity on Ir‐based alloys and these Ir‐based NFs hold great promise in future application in the PEMWE. [ABSTRACT FROM AUTHOR]

Electrocatalysis plays a crucial role in the transformation between electrical and chemical energy. Particularly, the search for high-performance electrocatalysts lies at the heart of numerous renewable energy conversion and storage technologies, such as water electrolysers and fuel cells, which potentially enable an energy-sustainable society. This Frontier article briefly describes the pathway from debates on "animal electricity" to the current understanding of electrocatalysis, and how knowledge can be harnessed to guide the discovery of well-defined electrocatalysts based on precious metal nanocrystals. We summarize basic design principles and key parameters associated with a good electrocatalyst and highlight the adoption of wet-chemical approaches for constructing nanocatalysts with desired structural properties. We close this article with personal perspectives on current challenges and future research directions in this field. [ABSTRACT FROM AUTHOR]

Abstract: Searching for highly efficient and durable electrocatalysts for the hydrogen evolution reaction (HER) that function effectively at all pHs is of great interest to the scientific community, however it is still a grand challenge, because the HER kinetics of Pt in alkaline solutions are approximately two to three orders of magnitude lower than that in acidic solution. Herein, a new class of wrinkled, ultrathin Rh2P nanosheets for enhancing HER catalysis at all pHs is reported. They exhibit a small overpotential of 18.3 mV at 10 mA cm−2, low Tafel slope of 61.5 mV dec−1, and good durability in alkaline media, much better than the commercial Pt/C catalyst. Density functional theory calculations reveal that the active open‐shell effect from the P‐3p band not only promotes Rh‐4d for increased proton–electron charge exchange but also provides excellent p–p overlapping to locate the O‐related species as distributary center, which can benefit the HER process in alkaline media. It is also demonstrated that the present wrinkled, ultrathin Rh2P nanosheets are highly efficient and durable electrocatalysts toward HER in both acid and neutral electrolytes. The present work opens a new material design for ultrathin 2D metal phosphide nanostructures for the purpose of boosting HER performance at all pHs. [ABSTRACT FROM AUTHOR]

Abstract: The development of high‐performance oxygen reduction reaction (ORR) catalysts derived from non‐Pt group metals (non‐PGMs) is urgent for the wide applications of proton exchange membrane fuel cells (PEMFCs). In this work, a facile and cost‐efficient supramolecular route is developed for making non‐PGM ORR catalyst with atomically dispersed Fe‐Nx/C sites through pyrolyzing the metal‐organic polymer coordinative hydrogel formed between Fe3+ and α‐L‐guluronate blocks of sodium alginate (SA). High‐angle annular dark field scanning transmission electron microscopy (HAADF‐STEM) and X‐ray absorption spectroscopy (XAS) verify that Fe atoms achieve atomic‐level dispersion on the obtained SA‐Fe‐N nanosheets and a possible fourfold coordination with N atoms. The best‐performing SA‐Fe‐N catalyst exhibits excellent ORR activity with half‐wave potential (E1/2) of 0.812 and 0.910 V versus the reversible hydrogen electrode (RHE) in 0.5 m H2SO4 and 0.1 m KOH, respectively, along with respectable durability. Such performance surpasses that of most reported non‐PGM ORR catalysts. Density functional theory calculations suggest that the relieved passivation effect of OH* on Fe‐N4/C structure leads to its superior ORR activity to Pt/C in alkaline solution. The work demonstrates a novel strategy for developing high‐performance non‐PGM ORR electrocatalysts with atomically dispersed and stable M‐Nx coordination sites in both acidic and alkaline media. [ABSTRACT FROM AUTHOR]

Ordered intermetallic alloys have attracted extensive attention as advanced electrocatalysts for polymer electrolyte membrane fuel cells (PEMFCs) reactions with much improved activity and stability. Here, latest progress in tuning intermetallic Pt- and Pd-based nanocrystals with tunable morphology and structure for catalyzing both the cathodic reduction of oxygen and anodic oxidation of fuels (e.g., methanol, ethanol and formic acid) in PEMFCs is highlighted. Making/tuning interesting intermetallic PtM (M = Fe, Co, Pb, Cu, etc.)-based nanocrystals for boosting oxygen reduction reaction with high activity and stability by using/controlling high-temperature annealing treatment is discussed. In all the reported Pt-based intermetallic nanocrystals, controlling the degree of ordering under the proper high temperature treatment is the key for achieving the optimized electrocatalysis. In order to search for cheaper catalysts, the progress on making Pd-based intermetallic nanocrystals is also discussed. Furthermore, future research directions are proposed and discussed to further enhance the efficiency of such unique intermetallic multimetallic nanocatalysts. This report aims to demonstrate the potential of ordered intermetallic strategy for boosting electrocatalysis and stimulating more research efforts in this field. [ABSTRACT FROM AUTHOR]

The development of superior non-platinum electrocatalysts for enhancing the electrocatalytic activity and stability for the oxygen-reduction reaction (ORR) and liquid fuel oxidation reaction is very important for the commercialization of fuel cells, but still a great challenge. Herein, we demonstrate a new colloidal chemistry technique for making structurally ordered PdCu-based nanoparticles (NPs) with composition control from PdCu to PdCuNi and PtCuCo. Under the dual tuning on the composition and intermetallic phase, the ordered PdCuCo NPs exhibit better activity and much enhanced stability for ORR and ethanol-oxidation reaction (EOR) than those of disordered PdCuM NPs, the commercial Pt/C and Pd/C catalysts. The density functional theory (DFT) calculations reveal that the improved ORR activity on the PdCuM NPs stems from the catalytically active hollow sites arising from the ligand effect and the compressive strain on the Pd surface owing to the smaller atomic size of Cu, Co, and Ni. [ABSTRACT FROM AUTHOR]

One of the critical issues in the industrial development of fuel cells (e.g., proton exchange membrane fuel cells, direct methanol fuel cells and biofuel cells) is the high cost, serious intermediate tolerance, anode crossover, sluggish kinetics, and poor stability of the platinum (Pt) as the preferred electrocatalysts for the oxygen reduction reaction (ORR) at the cathode. The development of novel noble-metal-free electrocatalysts with low cost, high activity and practical durability for ORR has been considered as one of the most active and competitive fields in chemistry and materials science. In this critical review, we will summarize recent advances on engineering advanced carbon nanomaterials with different dimensions for the rational design and synthesis of noble-metal-free oxygen reduction electrocatalysts including heteroatom-doped carbon nanomaterials, transition metal-based nanoparticle (NP)–carbon nanomaterial composites and especially the stable iron carbide (Fe3C)-based NP–carbon nanomaterial composites. Introducing advanced carbon nanomaterials with high specific surface area and stable structure into the noble-metal-free ORR field has not only led to a maximized electrocatalyst surface area for the electron transfer but also resulted in enhanced electrocatalyst stability for long-term operation. Therefore, the rational design and synthesis of noble-metal-free electrocatalysts based on heteroatoms, transition metal-based NPs and Fe3C-based NP functionalized carbon nanomaterials are of special relevance for their ORR applications, and represents a rapidly growing branch of research. The demonstrated examples in this review will open new directions on designing and optimizing advanced carbon nanomaterials for the development of extremely active and durable earth-abundant cathodic catalysts for fuel cell applications. [ABSTRACT FROM AUTHOR]

Replacing the rare and precious platinum (Pt) electrocatalysts with earth-abundant materials for promoting the oxygen reduction reaction (ORR) at the cathode of fuel cells is of great interest in developing high-performance sustainable energy devices. However, the challenging issues associated with non-Pt materials are still their low intrinsic catalytic activity, limited active sites, and the poor mass transport properties. Recent advances in material sciences and nanotechnology enable rational design of new earth-abundant materials with optimized composition and fine nanostructure, providing new opportunities for enhancing ORR performance at the molecular level. This Review highlights recent breakthroughs in engineering nanocatalysts based on the earth-abundant materials for boosting ORR. [ABSTRACT FROM AUTHOR]

An efficient synthetic approach that enables not only the control of Pt nanocubes but also the one-pot fabrication of novel Pt nanocube assemblies was developed for the first time. The integration of well-defined building blocks and unique superstructures endows Pt nanocube assemblies with enhanced performance in the methanol electrooxidation, showing a new concept for further enhancing the performance of these catalysts. [ABSTRACT FROM AUTHOR]

• 1D and 2D noble metal-based nanocrystals with various nanostructures are summarized. • Typical strategies for tuning the nanostructures of 1D and 2D noble metal-based nanocrystals are discussed. • The underlying mechanisms behind the structure-performance relationship are discussed. • Present challenges and perspectives to the research of 1D and 2D noble metal-based nanocrystals are provided. Recently, one- (1D) and two-dimensional (2D) noble metal-based nanocrystals have triggered tremendous interest due to their unique anisotropic structure in the field of electrochemical energy conversion. In this review, we summarize the latest research developments in 1D and 2D noble metal-based nanocrystals with various nanostructures, and their potential applications as electrocatalysts toward fuel-cell-related electrocatalysis. Five strategies including size, shape, composition, surface, and interface engineering are proposed to rationally design the nanoarchitectures of the 1D and 2D noble metal-based electrocatalysts. In addition, we also highlight the underlying mechanisms behind the structure-property relationship. Finally, we conclude the current challenges and give our perspectives on the development of high-performance 1D and 2D noble metal-based electrocatalysts. We hope this review could offer timely information on the research of 1D and 2D noble metal-based nanocrystals and provide guidance for regulating their electrocatalytic properties. [ABSTRACT FROM AUTHOR]

Despite intense research in past decades, the development of high‐performance bifunctional catalysts for direct ethylene glycol or glycerol oxidation reaction (EGOR or GOR) and oxygen reduction reaction (ORR) remains a grand challenge in realizing fuel‐cell technologies for portable electronic devices and fuel‐cell vehicle applications. Here, a general method is reported for controllable synthesis of a class of ultrathin multimetallic PtPdM (M = Ni, Fe, Co) nanosheets (NSs) with a thickness of only 1.4 nm by coreduction of metal precursors in the presence of CO and oleylamine. With the optimized composition and components, ultrathin Pt32Pd48Ni20 NSs exhibit the highest electrocatalytic activity for EGOR, GOR, and ORR among all different ultrathin PtPdM NSs, ultrathin PtPd NSs, and the commercial catalysts. The mass activities of ultrathin Pt32Pd48Ni20 NSs for EGOR, GOR, and ORR are 7.7, 5.4, and 7.7 times higher respectively than a commercial catalyst, and they are the most efficient nanocatalysts ever reported for EGOR/GOR. The ultrathin PtPdNi NSs are also very stable for EGOR/GOR/ORR. It is further demonstrated that these ultrathin multimetallic NSs can be readily generalized to other sensor‐related electrocatalysis system such as high‐sensitivity electrochemical detection of H2O2. A new class of high‐performance ultrathin PtPdM alloy nanosheets (NSs): A robust and general method for creating a new class of multimetallic PtPdM alloyNSs is developed. With the optimized composition and components, ultrathin Pt32Pd48Ni20 NSs exhibit the highest electrocatalytic activity for ethylene glycol oxidation reaction (EGOR), glycerol oxidation reaction (GOR), and oxygen reduction reaction, making them among the most efficient nanocatalysts ever reported for EGOR and GOR. [ABSTRACT FROM AUTHOR]

Pt-based 3D nanodendrites hold great promise as electrocatalysts for renewable energy technologies, yet encounter challenges associated with their structural fragility. This works addresses this challenge by constructing nanodendrites composed of thermally- and electrochemically-stable nanoplates, which enable the breakthrough of both activity and stability of dendrites-type electrocatalysts. Highly-branched dendritic Pt-based nanocrystals possess great potential in catalyzing the oxygen reduction reaction (ORR), but encounter performance ceiling due to their poor thermal and electrochemical stability. Here, we present a novel PtFe nanodendrites (NDs) branched with two-dimensional (2D) twinned nanoplates rather than conventional 1D nanowires, which breaks the ORR performance ceiling of dendritic catalysts by inducing the unique Pt-skin configuration via rationally thermal treatment. By further hybridizing the Pt-skin PtFe NDs/C with amino-functionalized ionic liquids (ILs), we achieve an unprecedented mass activity of 3.15 A/mg Pt at 0.9 V versus reversible hydrogen electrode (RHE) in the PtFe-based ORR electrocatalytic system. They also show excellent electrocatalytic durability for ORR with negligible activity decay and no apparent structural change after 20,000 cycles, in sharp contrast to the nanowires branched PtFe NDs counterpart. The remarkable catalytic performance is attributed to a combination of several structural features, including 2D morphology, twin boundary, partially ordered phase and strong coordination with amino group. This work highlights the significance of stabilizing electrocatalytic structures via morphology tuning, which thus enables further surface and interface modification for performance breakthrough in ORR electrocatalysis. [ABSTRACT FROM AUTHOR]