Cost-Effective Alkaline Water Electrolysis Based on Nitrogen- and Phosphorus-Doped Self-Supportive Electrocatalysts

Tuning Stainless Steel Oxide Layers through Potential Cycling─AEM Water Electrolysis Free of Critical Raw Materials

Anion exchange membrane water electrolyzers (AEMWEs) have an intrinsic advantage over acidic proton exchange membrane water electrolyzers through their ability to use inexpensive, stable materials such as stainless steel (SS) to catalyze the sluggish oxygen evolution reaction (OER). As such, the study of active oxide layers on SS has garnered great interest. Potential cycling is a means to create such active oxide layers in situ as they are readily formed in alkaline solutions when exposed to elevated potentials. Cycling conditions in the literature are rife with unexplained variations, and a complete account of how these variations affect the activity and constitution of SS oxide layers remains unreported, along with their influence on AEMWE performance. In this paper, we seek to fill this gap in the literature by strategically cycling SS felt (SSF) electrodes under different scan rates and ranges. The SSF anodes were rapidly activated within the first 50 cycles, as shown by the 10-fold decline in charge transfer resistance, and the subsequent 1000 cycles tuned the metal oxide surface composition. Cycling the Ni redox couple (RC) increases Ni content, which is further enhanced by lowering the cycling rate, while cycling the Fe RC increases Cr content. Fair OER activity was uncovered through cycling the Ni RC, while Fe cycling produced SSF electrodes active toward both the OER and the hydrogen evolution reaction (HER). This indicates that inert SSF electrodes can be activated to become efficient OER and HER electrodes. To this effect, a single-cell AEMWE without any traditional catalyst or ionomer generated 1.0 A cm-2 at 1.94 V ± 13.3 mV with an SSF anode, showing a fair performance for a cell free of critical raw materials.

In-situ fabrication of Cr doped FeNi LDH on commercial stainless steel for oxygen evolution reaction

Commercial stainless steel has attracted increasing interest due to their rich content in transition metal elements and corrosion resistance properties. In this work, we design a facile and rapid route to in-situ fabricate the Cr doped FeNi layered double hydroxides nanosheets (LDHs) on modified stainless steel (Cr-FeNi LDH @ ESS) under ambient condition.The ultra small scaled 2D structure only around 20 nm diameter and metal ions with multivalent oxidation state were observed on the in situ fabricated LDHs, which provides high active area and active sites and thus promote excellent oxygen evolution reaction (OER). The Cr-FeNi LDH @ESS electrocatalysts exhibit an over potential of 280 mV at 10 mA cm-2 and achieves a Tafel slope of 44 mV dec-1 for OER in the 1.0 M KOH aqueous solution. We anticipate that the operating strategy of our system may promote the development of commercial non-precious productions as the efficient electrocatalysts for energy storage and conversion.

Practical Electrochemical Method to Enhance Needle Visibility during Ultrasound Imaging

Ultrasound-guided needle interventions play a pivotal role in the diagnosis and treatment processes in clinical practice. However, existing echogenic needles face challenges in achieving a balance between effectiveness, ease of manufacturing, and inexpensiveness. In this study, we developed an echogenic needle that encompassed the aforementioned advantages through the use of the electrolysis technology. The overall contour of the needle after electrolysis was observed using bright-field microscopy, while scanning electron microscopy (SEM) was employed to examine the micro-variations on the needle's surface. Subsequently, we validated the enhanced visualization effects in vitro (pork) and in vivo (anesthetized rabbit's thigh) puncture phantoms. To ensure the safety of the needles after the puncture procedure, we conducted Vickers hardness tests, SEM detection, bright-field microscopy, and DAPI staining. The results demonstrated that the surface roughness of the needle increased with the duration of electrolysis. Taking into account the comprehensive safety tests, the needle, subjected to 40 s of electrolysis, demonstrated a safe and effective enhancement of ultrasound visualization.

Mo2C promoted electrocatalysis of the Pt/Mo2C (C) heterostructure for a superior hydrogen evolution reaction

Constructing a unique electrochemical interface to enhance the catalytic capacity of Pt-based catalysts is indispensable for wider application of the hydrogen evolution reaction (HER). Herein, platinum-analogous molybdenum carbide (Mo₂C) was combined with a lower content of Pt to construct the Pt/Mo₂C (C) heterostructure via a solid-phase method, using ammonium molybdate as the precursor. Vulcan-C served as a support to promote the distribution of the Pt and Mo₂C heterostructure, and cooperative effects between Pt and the Mo₂C heterostructure contributed to the significantly improved catalytic capacity of Pt. The obtained Pt/Mo₂C (C) exhibits superior HER activity and enhanced long-term durability in the acidic medium, with a low overpotential of 38 mV at 10 mA cm^-2 and a low Tafel slope of 24 mV dec^-1. In particular, a drastically enhanced amount of H₂ production can be achieved (6837.28 mmol h^-1 g^-1). This facile approach not only provides a new pathway for constructing novel heterostructures but also gives an insight into the design of cost-effective Pt-based materials for an efficient HER.

Research on engineered electrocatalysts for efficient water splitting: a comprehensive review

Water electrolysis plays an interesting role toward hydrogen generation for overcoming global environmental crisis and solving the energy storage problem. However, there is still a deficiency of efficient electrocatalysts to overcome sluggish kinetics for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Great efforts have been employed to produce potential catalysts with low overpotential, rapid kinetics, and excellent stability for HER and OER. At present, hydrogen economy is driven by electrocatalysts with excellent characteristics; thus, systematic design strategy has become the driving force to exploit earth-abundant transition metal-based electrocatalysts toward H₂ economy. In this review, the recent progress on newer materials including metals, alloys, and transition metal oxides (manganese oxides, cobalt oxides, nickel oxides, PBA-derived metal oxides, and metal complexes) as photocatalysts/electrocatalysts has been overviewed together with some methodologies for efficient water splitting. Metal-organic framework (MOF)-based electrocatalysts have been highly exploited owing to their interesting functionalities. The photovoltaic-electrocatalytic (PV-EC) process focused on harvesting high solar-to-hydrogen efficiency (STH) among various solar energy conversion as well as storage systems. Electrocatalysts/photocatalysts with high efficiency have become an urgent need for overall water splitting. Also, cutting-edge achievements in the fabrication of electrocatalysts along with theoretical consideration have been discussed.

Tuning Mass Transport in Electrocatalysis Down to Sub-5 nm through Nanoscale Grade Separation

Nano and single-atom catalysis open new possibilities of producing green hydrogen (H₂ ) by water electrolysis. However, for the hydrogen evolution reaction (HER) which occurs at a characteristic reaction rate proportional to the potential, the fast generation of H₂ nanobubbles at atomic-scale interfaces often leads to the blockage of active sites. Herein, a nanoscale grade-separation strategy is proposed to tackle mass-transport problem by utilizing ordered three-dimensional (3d) interconnected sub-5 nm pores. The results reveal that 3d criss-crossing mesopores with grade separation allow efficient diffusion of H₂ bubbles along the interconnected channels. After the support of ultrafine ruthenium (Ru), the 3d mesopores are on a superior level to two-dimensional system at maximizing the catalyst performance and the obtained Ru catalyst outperforms most of the other HER catalysts. This work provides a potential route to fine-tuning few-nanometer mass transport during water electrolysis.

In-site hydrogen bubble template method to prepare Ni coated metal meshes as effective bi-functional electrodes for water splitting

Metal substrates are frequently used as current collectors and supports for electrochemically active materials, but their effect on the physical and electrochemical performance of electrocatalysts is rarely investigated. In this study, the electrodeposition method was used to coat four different metal meshes with three-dimensional nickel porous structures using hydrogen bubbles as a template. The significant influence of the metal substrates on the morphology of deposited nickel was demonstrated. 3D porous structures formed on nickel, iron, copper, and titanium meshes via the hydrogen bubble template method varied significantly. It was found that differences in the physical adsorption of hydrogen and electrochemical hydrogen evolution on metal substrates are the fundamental reasons behind the diverse morphology of the coatings. Lattice matching of the substrate and the active material also plays an important role during the electrodeposition process. Electrocatalytic performance of the newly prepared materials in water electrolysis was evaluated using the hydrogen and oxygen evolution reactions (HER and OER). The results demonstrate the high electrocatalytic activity of Ni/FeM in the OER and HER, and the good stability of Ni/TiM in HER.

Water electrolysis: from textbook knowledge to the latest scientific strategies and industrial developments

Replacing fossil fuels with energy sources and carriers that are sustainable, environmentally benign, and affordable is amongst the most pressing challenges for future socio-economic development. To that goal, hydrogen is presumed to be the most promising energy carrier. Electrocatalytic water splitting, if driven by green electricity, would provide hydrogen with minimal CO2 footprint. The viability of water electrolysis still hinges on the availability of durable earth-abundant electrocatalyst materials and the overall process efficiency. This review spans from the fundamentals of electrocatalytically initiated water splitting to the very latest scientific findings from university and institutional research, also covering specifications and special features of the current industrial processes and those processes currently being tested in large-scale applications. Recently developed strategies are described for the optimisation and discovery of active and durable materials for electrodes that ever-increasingly harness first-principles calculations and machine learning. In addition, a technoeconomic analysis of water electrolysis is included that allows an assessment of the extent to which a large-scale implementation of water splitting can help to combat climate change. This review article is intended to cross-pollinate and strengthen efforts from fundamental understanding to technical implementation and to improve the 'junctions' between the field's physical chemists, materials scientists and engineers, as well as stimulate much-needed exchange among these groups on challenges encountered in the different domains.

Engineering Microdomains of Oxides in High-Entropy Alloy Electrodes toward Efficient Oxygen Evolution

One important goal of the current electrocatalysis is to develop integrated electrodes from the atomic level design to multilevel structural engineering in simple ways and low prices. Here, a series of oxygen micro-alloyed high-entropy alloys (O-HEAs) is developed via a metallurgy approach. A (CrFeCoNi)₉₇ O₃ bulk O-HEA shows exceptional electrocatalytic performance for the oxygen evolution reaction (OER), reaching an overpotential as low as 196 mV and a Tafel slope of 29 mV dec^-1 , and with stability longer than 120 h in 1 m KOH solution at a current density of 10 mA cm^-2 . It is shown that the enhanced OER performance can be attributed to the formation of island-like Cr₂ O₃ microdomains, the leaching of Cr³⁺ ions, and structural amorphization at the interfaces of the domains. These findings offer a technological-orientated strategy to integrated electrodes.

Constructing Ultrathin W-Doped NiFe Nanosheets via Facile Electrosynthesis as Bifunctional Electrocatalysts for Efficient Water Splitting

Exploring cost-effective and efficient bifunctional electrocatalysts via simple fabrication strategies is strongly desired for practical water splitting. Herein, an easy and fast one-step electrodeposition process is developed to fabricate W-doped NiFe (NiFeW)-layered double hydroxides with ultrathin nanosheet features at room temperature and ambient pressure as bifunctional catalysts for water splitting. Notably, the NiFeW nanosheets require overpotentials of only 239 and 115 mV for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively, to reach a current density of 10 mA/cm² in alkaline media. Their exceptional performance is further demonstrated in a full electrolyzer configuration with the NiFeW as both anode and cathode catalysts, which achieves a low cell voltage of 1.59 V at 10 mA/cm², 110 mV lower than that of the commercial IrO₂ (anode) and Pt (cathode) catalysts. Moreover, the NiFeW nanosheets are superior to various recently reported bifunctional electrocatalysts. Such remarkable performances mainly ascribe to W doping, which not only effectively modulates the electrocatalyst morphology but also engineers the electronic structure of NiFe hydroxides to boost charge-transfer kinetics for both the OER and HER. Hence, the ultrathin NiFeW nanosheets with an efficient fabrication strategy are promising as bifunctional electrodes for alkaline water electrolyzers.

Recent advances of noble-metal-free bifunctional oxygen reduction and evolution electrocatalysts

Bifunctional oxygen reduction and evolution constitute the core processes for sustainable energy storage. The advances on noble-metal-free bifunctional oxygen electrocatalysts are reviewed.

Electrodeposition of Ni3Se2/MoSex as a bifunctional electrocatalyst towards highly-efficient overall water splitting

Electrochemically splitting water into hydrogen and oxygen plays a significant role in the commercialization of hydrogen energy as well as fuel cells, but it remains a challenge to design and fabricate low-cost and high-efficiency electrocatalysts. Herein, we successfully prepared Ni3Se2/MoSex on nickel foam via a facile electrodeposition method. To understand the electrochemical mechanism occurring in the electrodeposition process, a new model was proposed, providing insight into the nucleation and growth of deposited materials. The as-prepared Ni3Se2/MoSex exhibits splendid electrochemical performance with 82 mV and 270 mV overpotentials to drive a current density of 10 mA cm-2 in 1 M KOH aqueous solution for HER and OER, respectively. Moreover, a driving potential of 1.57 V is required to reach a current density of 10 mA cm-2 for a configured full cell with Ni3Se2/MoSex working as both the anode and cathode towards overall water splitting, outperforming the state-of-the-art commercial full cells assembled with noble-based metals. The advanced catalytic performance should be attributed to the numerous in situ formed interfaces, allowing π-electron transfer from Ni to Mo via O2- bridging, subsequently optimizing the adsorption features of oxygenated species (OER) and favorable Volmer/Heyrovsky reaction (HER). This work offers an effective and scalable fabrication prototype for the preparation of bifunctional electrocatalysts with electrodeposition.

Lattice-Strain Engineering of Homogeneous NiS0.5 Se0.5 Core-Shell Nanostructure as a Highly Efficient and Robust Electrocatalyst for Overall Water Splitting

Developing highly-efficient non-noble-metal electrocatalysts for water splitting is crucial for the development of clean and reversible hydrogen energy. Introducing lattice strain is an effective strategy to develop efficient electrocatalysts. However, lattice strain is typically co-created with heterostructure, vacancy, or substrate effects, which complicate the identification of the strain-activity correlation. Herein, a series of lattice-strained homogeneous NiS_x Se_{1- x} nanosheets@nanorods hybrids are designed and synthesized by a facile strategy. The NiS_0.5 Se_0.5 with ≈2.7% lattice strain exhibits outstanding activity for hydrogen and oxygen evolution reaction (HER/OER), affording low overpotentials of 70 and 257 mV at 10 mA cm^-2 , respectively, as well as excellent long-term durability even at a large current density of 100 mA cm^-2 (300 h), significantly superior to other benchmarks and the precious metal catalysts. Experimental and theoretical calculation results reveal that the generated lattice strain decreases the metal d-orbital overlap, leading to a narrower bandwidth and a closer d-band center toward the Fermi level. Thus, NiS_0.5 Se_0.5 possesses favorable H* adsorption kinetics for HER and lower energy barriers for OER. This work provides a new insight to regulate the lattice strain of advanced catalyst materials and further improve the performance of energy conversion technologies.

Surface-coordinated metal-organic framework thin films (SURMOFs) for electrocatalytic applications

The design and development of highly efficient electrocatalysts are very important in energy storage and conversion. As a kind of inorganic organic hybrid material, metal-organic frameworks (MOFs) have been used as electrocatalysts in electrocatalytic reactions due to their structural diversities and fascinating functionalities. Particularly, MOF thin films are coordinated on substrate surfaces by a liquid phase epitaxial (LPE) layer by layer (LBL) growth method (called surface-coordinated MOF thin films, SURMOFs), and recently have been studied in various applications due to their precisely controlled thickness, preferred growth orientation and homogeneous surface. In this review, we will summarize the preparation and electrocatalysis of SURMOFs and their derived thin films (SURMOF-D). The SURMOF based thin films possess diverse topological structures and flexible properties, providing abundant catalytically active sites and fast charge transfer for efficient electrocatalytic performance in the oxygen evolution reaction (OER), oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), carbon dioxide reduction reaction (CRR), supercapacitors, tandem electrocatalysis and so on. The research challenges and problems of SURMOFs for electrocatalytic applications are also discussed at the end of the review.

Ligand-assisted capping growth of self-supporting ultrathin FeNi-LDH nanosheet arrays with atomically dispersed chromium atoms for efficient electrocatalytic water oxidation

Self-supporting ultrathin FeNi-layered double hydroxide nanosheet arrays with atomically dispersed Cr atoms were firstly fabricated from stainless steel mesh by a facile ligand-assisted capping growth approach. Their unique nanostructure and a strong synergetic effect between the atomically dispersed Cr dopants and the active sites afford an exceptional OER activity.

Three-Dimensional N-Doped Carbon Nanotube Frameworks on Ni Foam Derived from a Metal-Organic Framework as a Bifunctional Electrocatalyst for Overall Water Splitting

Rational design of bifunctional, high-performance, and stable non-noble metal-based electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of great importance and challenging for the realization of overall water splitting. Metal-organic frameworks (MOFs) have been intensively studied as pyrolyzing precursors to prepare electrocatalysts. However, the aggregation of powder and the low conductivity of polymer binders have limited the applications of powder electrocatalysts. Therefore, the direct growth of MOFs on conductive and porous substrates will be a favorable way to prepare efficient electrocatalysts for electrocatalytic water splitting. Herein, we report a facile strategy for constructing three-dimensional N-doped carbon nanotube frameworks derived from metal-organic framework on Ni foam as a bifunctional electrocatalyst for overall water splitting. The resulting electrocatalyst exhibits excellent stability and high OER and HER activity with rather low overpotentials of 230 and 141 mV at 10 mA/cm² in 1.0 M KOH, respectively. Specifically, the as-synthesized electrodes were used as both the cathode and anode for overall water splitting with 10 mA/cm² at a cell voltage of only 1.62 V. The outstanding electrocatalytic performance is mainly attributed to a large number of accessible active sites of Co nanoparticles dispersed by the N-doped carbon nanotubes (CNTs) and the ultra-high surface area of CNT frameworks. The presented strategy offers a novel approach for developing MOF-derived nanocarbon materials on Ni foam for electrocatalysis and electrochemical energy devices.

Enhancing hydrogen evolution reaction through modulating electronic structure of self-supported NiFe LDH

NiFe-layered double hydroxide (NiFe LDH), as an efficient oxygen evolution reaction (OER) electrocatalyst, has emerged as a promising electrocatalyst for catalyzing overall water splitting in alkaline electrolyte.

Non-precious-metal catalysts for alkaline water electrolysis: operando characterizations, theoretical calculations, and recent advances

Advances of non-precious-metal catalysts for alkaline water electrolysis are reviewed, highlighting operando techniques and theoretical calculations in their development.

Electro-deposition of nickel–iron nanoparticles on flower-like MnCo2O4 nanowires as an efficient bifunctional electrocatalyst for overall water splitting

The obtained NiFe–MnCo₂O₄/NFF electrode exhibited superior electrocatalytic performance and extraordinary durability for the OER, HER, and overall water splitting.

Self-Supportive Mesoporous Ni/Co/Fe Phosphosulfide Nanorods Derived from Novel Hydrothermal Electrodeposition as a Highly Efficient Electrocatalyst for Overall Water Splitting

Low cost and highly efficient bifuctional catalysts for overall water electrolysis have drawn considerable interests over the past several decades. Here, rationally synthesized mesoporous nanorods of nickel-cobalt-iron-sulfur-phosphorus composites are tightly self-supported on Ni foam as a high-performance, low cost, and stable bifunctional electrocatalyst for water electrolysis. The targeted designing and rational fabrication give rise to the nanorod-like morphology with large surface area and excellent conductivity. The NiCoFe-PS nanorod/NF can reach 10 mA cm^-2 at a small overpotential of 195 mV with a Tafel slope of 40.3 mV dec^-1 for the oxygen evolution reaction and 97.8 mV with 51.8 mV dec^-1 for the hydrogen evolution reaction. Thus, this bifunctional catalyst shows low potentials of 1.52 and 1.76 V at 10 and 50 mA cm^-2 toward overall water splitting with excellent stability for over 200 h, which are superior to most non-noble metal-based bifunctional electrocatalysts recently. This work provides a new strategy to fabricate multiple metal-P/S composites with the mesoporous nanorod-like structure as bifunctional catalysts for overall water splitting.

Robust Photoelectrochemical Oxygen Evolution with N, Fe-CoS2 Nanorod Arrays

Photoelectrochemical water splitting is a promising approach to enhance the efficiency of water splitting. However, it is still challenging to develop an efficient oxygen evolution reaction (OER) electrocatalyst that can be coupled with light due to inefficient light utilization. Here, we demonstrate that N, Fe-co-doped CoS₂ (N, Fe-CoS₂) nanorod arrays can act as a highly efficient photo-coupled electrochemical OER catalyst. In dark conditions, the N, Fe-doped CoS₂ on self-supported stainless steel (SS) mesh shows a small OER overpotential (215 mV) at a current density of 10 mA cm^-2, a reduced Tafel slope (43.2 mV dec^-1), and negligible activity decay after 10 000 cycles. Upon visible-NIR light illumination, the N, Fe-doped anode exhibits superior photoelectrochemical performance because of the enhanced photoresponse, excellent light harvesting ability and promoted interfacial kinetics of charge separation. Our well-designed photoelectrochemical OER electrode can not only serve as a light absorption semiconductor but also the active catalytic sites for the OER reaction; the electrode composed of the single phase can efficiently avoid photocarrier recombination at the grain boundary. This study provides an insight into photoanode synthesis for photoelectrochemical OER and offers guidance on the future electrocatalyst design.

A Simple and Scalable Approach To Remarkably Boost the Overall Water Splitting Activity of Stainless Steel Electrocatalysts

The stainless steel mesh (SSM) has received growing consideration as an electrocatalyst for efficient hydrogen and oxygen evolution reactions. Recently, the application of SSM as an oxygen evolution reaction (OER) electrocatalyst has been more promising, while its hydrogen evolution reaction (HER) catalytic activity is very low, which definitely affects its overall water splitting activity. Herein, a simple chemical bath deposition (CBD) method followed by phosphorization is employed to significantly boost the overall water splitting performance of SSM. The CBD method could allow the voids between the SSM fibers to be filled with Ni and P. Electrocatalytic studies show that the CBD-treated and phosphorized stainless steel (denoted SSM-Ni-P) exhibits an HER overpotential of 149 mV, while the phosphorization-free CBD-treated SSM (denoted as SSM-Ni) delivers an OER overpotential of 223 mV, both at a current density of 10 mA cm^-2. An asymmetric alkaline electrolyzer assembled based on the SSM-Ni-P cathode (HER) and SSM-Ni anode (OER) achieved an onset and 10 mA cm^-2 current densities at an overall potential of 1.62 V, granting more prospects for the application of inexpensive and highly active electrocatalysts for electrocatalytic water splitting reactions.

Direct Growth of CNTs@CoSx Se2(1-x) on Carbon Cloth for Overall Water Splitting

Searching for low-cost, high-efficiency, bifunctional, non-noble-metal electrocatalysts for overall water splitting is crucial to renewable energy conversion. Herein, a series of component-controllable CC/CNTs@CoS_x Se_2(1-x) (CC: carbon cloth, CNT: carbon nanotube) with excellent bifunctional properties in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) were obtained by chemical vapor deposition. In this strategy, the Zif-67 precursor served as a structural inducer, which was directly grown on CC and pyrolyzed with the assistance of melamine to form multi-walled CNT-encapsulated CoS_x Se_2(1-x) hierarchical nanostructures. Subsequently, the electrocatalytic properties of the as-prepared materials were optimized by adjusting the S/Se molar ratio. Of note is that the lattice distortion caused by the different radii of Se and S generated a polarized electric field for easy adsorption of the intermediate products. The CoOOH generated in situ on the surface of CoS_x Se_2(1-x) , as well as n- and p-type domains in carbon, synergistically resulted in abundant active sites to boost the electrocatalytic activity. CC/CNTs@CoS_0.74 Se_0.52 exhibited overpotentials for the HER and OER of 225 and 285 mV, respectively and attained a current density of 10 mA cm^-2 in alkaline solution. The as-prepared electrocatalysts could act as both cathode and anode in a water electrolyzer showing a cell voltage of 1.74 V and delivering 10 mA cm^-2 , comparable to those of noble-metal-based water electrolyzers.

Fluorographdiyne: A Metal-Free Catalyst for Applications in Water Reduction and Oxidation

A highly efficient bifunctional metal-free catalyst was prepared by growth of three-dimensional porous fluorographdiyne networks on carbon cloth (p-FGDY/CC). Our experiments and density functional theory (DFT) calculations show the 3D p-FGDY/CC network is highly active and it is a high potential metal-free catalyst for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), as well as overall water splitting (OWS) under both acidic and alkaline conditions. The experimental and theoretical results show very good consistency; for example, in the HER process, p-FGDY/CC exhibits small overpotentials of 82 and 92 mV to achieve 10 mA cm^-2 under alkaline and acidic conditions, respectively. This ensures an even higher selectivity for the adsorption/desorption of various O/H intermediate species. The essential key promotion accomplishes a bifunctional H₂ O redox performance application under pH-universal electrochemical conditions.

Co3 O4 @Cu-Based Conductive Metal-Organic Framework Core-Shell Nanowire Electrocatalysts Enable Efficient Low-Overall-Potential Water Splitting

In the work reported herein, the electrocatalytic properties of Co₃ O₄ in hydrogen and oxygen evolution reactions have been significantly enhanced by coating a shell layer of a copper-based metal-organic framework on Co₃ O₄ porous nanowire arrays and using the products as high-performance bifunctional electrocatalysts for overall water splitting. The coating of the copper-based metal-organic framework resulted in the hybridization of the copper-embedded protective carbon shell layer with Co₃ O₄ to create a strong Cu-O-Co bonding interaction for efficient hydrogen adsorption. The hybridization also led to electronically induced oxygen defects and nitrogen doping to effectively enhance the electrical conductivity of Co₃ O₄ . The optimal as-prepared core-shell hybrid material displayed excellent overall-water-splitting catalytic activity that required overall voltages of 1.45 and 1.57 V to reach onset and a current density of 10 mA cm^-2 , respectively. This is the first report to highlight the relevance of hybridizing MOF-based co-catalysts to boost the electrocatalytic performance of nonprecious transition-metal oxides.