Electrochemical Active Surface Area Research Articles

Interface Engineering of Flower-like Co 2 P/WO 3-x /Carbon Cloth Catalysts with Oxygen Vacancies for Efficient Oxygen Evolution Reaction.

The Constructing an efficient and low-cost oxygen evolution reaction (OER) electrocatalyst is critical for improving the performance of electrolysis in alkaline water. In this study, a self-supported electrocatalyst of flower-like cobalt phosphide and tungsten oxide (Co2P/WO3-x/CC) was prepared on carbon cloth (CC)surface by hydrothermal reaction with solution immersion etching and phosphorization annealing under H2/Ar atmosphere. This strategy can generate oxygen vacancies (OV), improving the speed of charge transfer between cobalt phosphide (Co2P) and tungsten oxide (WO3-x) components. The catalyst greatly increases the electrochemical active surface area, which is beneficial for efficient oxygen evolution. Electrochemical testing studies show that in 1.0 M KOH solution, Co2P-WO3-x/CC catalyst exhibits good OER activity, with a low overpotential of 254 mV at 10 mA cm-2, a small Tafel slope of 58.32 mV dec-1. The synergistic effect of oxygen vacancies and Co2P with WO3-xcan regulate electronic structures, expose more active sites, and cooperatively enhancing the OER activity. This study provides a workable strategy for preparing efficient non-noble metal OER electrocatalysts on engineered interfaces and OV.

Pt Nanoparticles on Multi-Walled Carbon Nanotubes with High CO Tolerance for Methanol Electrooxidation

Anode catalysts are important for direct methanol fuel cells (DMFCs) of energy conversion. Herein, we report a novel strategy by ethylene glycol-based deep eutectic solvents (EG-DESs) for the fabrication of a multi-walled carbon nanotubes (MWCNTs)-supported Pt nanoparticles catalyst (referred to as Pt/CNTs-EG-DES). The Pt/CNTs-EG-DES catalyst provides an increased electrochemically active surface area (ECSA) and shows remarkably improved electrocatalytic performance towards methanol oxidation reaction compared to Pt/CNTs-W (fabricated in water) and commercial Pt/C catalysts. The improved performance is attributed to the generation of more Pt–O bonds which change the electronic states of the Pt atoms and the special node structure that obtains more active sites for a high CO resistance. This study suggests an effective synthesis strategy for Pt-based electrocatalysts with high performance for DMFC applications.

Nanoarchitectonics of Nickel Nitride‐V2CTX Mxene: An Efficient Bifunctional Catalyst for Alkaline Water/Seawater Applications

AbstractSeawater, being the most plentiful natural water source worldwide, is a highly abundant and cost‐efficient medium for producing hydrogen by alkaline water electrolysis. However, the advancement of seawater electrolysis is hindered by notable impediments caused by chloride corrosion at the anode and the simultaneous chlorine evolution process. Only a limited number of non‐noble electrocatalysts demonstrate noteworthy bifunctional catalytic efficacy and long‐term durability. In this regard, Nickel Nitride tailored V2CTX Mxene nanostructures is reported as a bifunctional catalyst for overall water/seawater applications. The optimized sample Ni3N@3000‐V2CTx exhibits low overpotential values of 90 and 300 mV in acidic and alkaline + seawater solutions respectively at 10 mA cm−2 for hydrogen evolution reaction. Similarly, this catalyst shows 70 and 240 mV overpotential values in alkaline water and alkaline + seawater solutions respectively at the same current density for oxygen evolution reaction. Synergetic effects of Multiple Vanadium and Nickel valency along with compelling nitrogen bonds creates elevated density of exposed functional sites for electrocatalytic activity. Furthermore, the notable electrochemical active surface area and mass activity suggest an enhanced and significant presence of abundant active sites. Additionally, the high stability and significantly decreased charge transfer resistance expedited the overall water/seawater‐splitting reaction rate.

Chirality Engineering of Nanostructured Copper Oxide for Enhancing Oxygen Evolution from Water Electrolysis.

The exploration of a new conceptual strategy for improving the oxygen evolution reaction (OER) of earth-abundant electrocatalysts is critical. In this study, chiral copper oxide nanoflower is explored by a self-assembly method. The characterization suggests the chiral structure originates from the crystal plane-level helical stack of the secondary nanosheets. Of note, the assembly illustrates a record-high degree of spin polarization of 96%, indicating the ideal alignment of electron spin. Moreover, density function theory calculations show the chiral structure reducing the reaction energy barrier (REB) while switching the potential-determining step from *O→*OOH to *OH→*O. Together with the enhanced electrochemical active surface area and accelerated charge transfer, the production of ground-state triplet O2 is improved via a spin-forbidden route that involves the singlet H2O/OH•. Consequently, the chiral nanoflower shows a overpotential of 308mV at 10mA cm-2 and a Tafel slope of 93.5mV dec-1, which is even superior to the commercial RuO2 (310mV, 101mV dec-1). This study presents a new strategy for improving the OER activity by simultaneously enhancing electronic properties and lowering the REB of an non-noble electrocatalyst via chirality engineering.

Modification Of a Screen-Printed Carbon Electrode with Nanoporous Gold by Electrodeposition and Dealloying of a Gold-Copper Alloy

In this study, a three-dimensional structure of nanoporous gold (NPG) was made by selectively corroding copper (Cu) from gold-copper (Au-Cu) alloys using a two-step electrochemical method. Given its large surface area and interconnected porous network, nanoporous gold is a suitable material for the advancement of electrochemical sensors. The screen-printed carbon electrode (SPCE) modified with nanoporous gold (NPG/SPCE) was fabricated by electrodepositing a gold-copper alloy from gold ion (Au3+) and copper ion (Cu2+) solution via cyclic voltammetry (CV) by scanning from -0.3 V to -0.8 V for 80 cycles. The copper is then removed via a dealloying process in 3M HNO3 using the cyclic voltammogram (CV) method by scanning potential from 0 V to +1.0 V for 100 cycles at 100 mV/s. The morphology, elemental composition, and electrochemical active surface area (ECSA) of NPG/SPCE electrodes were characterized using FESEM, EDX, and CV analysis, respectively. The electrochemical performance of the NPG/SPCE was compared with bare SPCE in a 10 mM potassium ferrocyanide (K4FeCN6) solution using cyclic voltammetry. The morphological study using FESEM revealed that the NPG/SPCE had an average pore diameter of 53 nm. The quantification of elements using EDX shows that 84 % of the copper in the electrodeposited gold-copper alloy electrode was successfully removed by the dealloying process. The higher number of cycles during the dealloying process led to producing NPG with higher ECSA electrodes. The ECSA of NPG/SPCE is 12 times greater than that of bare or unmodified SPCE in an equivalent geometrical area. NPG/SPCE has a much better electron transfer surface than bare SPCE due to its high surface area and gold surface properties, making it a potential sensing material for biosensing applications.

Intercalation of g-C3N4/Ag2S heterostructure on boronized Ni-MOF for enhanced water splitting and energy storage applications

The increasing global demand for energy conversion and storage technologies including water electrolysis, fuel cells, batteries & supercapacitors depend critically on the performance of their electrode components. Metal Organic Frameworks (MOFs), particularly Nickel Zeolite Imidazole Frameworks (Ni-ZIF) have drawn significant attention due to their greater electrocatalytic performance. Still, their restricted active sites & stability hinder their broader implementation in alkaline/saline water electrolysis & supercapacitor applications. Here, we are reporting the intercalation of heterostructure consisting of silver sulfide (Ag2S)/graphitic carbon nitride (g-C3N4) on Boronized Ni-ZIF (B:NZ) for empowered alkaline/saline water splitting and supercapacitor applications. These heterostructure addition over Boronized Ni-ZIF demonstrated minimal overpotentials for the oxygen evolution reaction (OER) (324 mV at 10.0 mA cm-2) and the hydrogen evolution reaction (HER) (78 mV at 10.0 mA cm-2) in alkaline medium (1 M KOH). The observed improvement in activity is ascribed to the decreased charge transfer resistance (Rct) & the augmented electrochemical active surface area (ECSA). Furthermore, Ag2S/g-C3N4/Boronized Ni-ZIF exhibited high specific capacitances of 1076.6 F/g and areal capacitance of 2584 F/cm2 at 0.50 A g-1 in supercapacitor applications. The incorporation of the g-C3N4 layer has enhanced the surface area and roughness facilitating stronger adhesion between hybrid layers which in turn resulted in prolonged stability exceeding 20 h in water splitting and 86 % retention in supercapacitor application.

Evaluating the Intrinsic Zinc Storage Capacity of Cation-Preintercalated Cathode with Electrochemically Active Surface Area.

The guest cation preintercalation strategy has been widely adopted to improve the performance of zinc-vanadium batteries. However, existing studies always ignore the deintercalation of guest cations. This work focuses on the severe and universal deintercalation phenomenon and confirms the unaltered capacity after deintercalation, indicating that the capacity improvement mechanism cannot be attributed to the role of guest cations. Therefore, after excluding all of the previously researched factors for capacity improvement, the decisive factor is identified as the morphology (surface area). Based on the electrochemically active surface area (ECSA), a quantitative relationship with intrinsic capacity is established for the first time. This guides us to enhance battery capacity via enhancing ECSA through liquid-phase ultrasonic crushing to achieve the highest capacity of cation-preintercalated V2O5·nH2O (333.7 mAh g-1 at 10 A g-1). We believe that the enhanced ECSA is a plausible explanation for the improved performance of hydrated vanadium oxides.

Simultaneous accelerated stress testing of membrane electrode assembly components in polymer electrolyte fuel cells

The durability of polymer electrolyte fuel cells (PEFCs) in fuel cell electric vehicles is important for the shift from passenger cars to heavy-duty vehicles. The components of a PEFC, namely the proton exchange membrane (PEM), catalyst layer (CL), and gas diffusion layer (GDL), contribute to the degradation of the fuel cell performance. In this paper, we propose a method for simultaneously evaluating the degradation rates of these components by combining electrochemical characterization with operando synchrotron X-ray radiography. The open-circuit voltage, electrochemically active surface area (ECSA), and water saturation were used as the degradation indicators for the PEMs, CLs, and GDLs, respectively. The results of two accelerated stress tests (loading and start-stop cycles) after 10,000 cycles showed that the increase in water saturation owing to the loss of hydrophobicity due to carbon corrosion in the cathode GDL occurred on the same timescale as the degradation in the PEM and cathode CL. Specifically, during the load cycle AST, the cathode CL degraded with a 26% reduction in the ECSA along with the cathode GDL degradation with a 10% increase in water saturation. This suggests that more efforts should be devoted to studies on the durability of GDLs for heavy-duty applications.

Unlocking the Electrocatalytic Behavior of Cu2MnS2 Nanoflake-Anchored rGO for the Oxygen Evolution Reaction in an Alkaline Medium.

A catalyst of the oxygen evolution reaction (OER) that is viable, affordable, and active for effective water-splitting applications is critical. A variety of electrocatalysts have been discovered to replace noble metal-based catalysts. Of these, transition metal-based sulfides are essential for incorporating carbonaceous materials to improve electrical conductivity, resulting in better electrocatalytic performance. Our study illustrates the synthesis of Cu2MnS2 (CMS) nanoflakes and their different rGO composites (10 to 40 wt %) via a hydrothermal technique for an effective water oxidation reaction. The X-ray diffraction pattern reveals that the prepared Cu2MnS2 nanoflakes exhibit a cubic crystal structure. The high-resolution scanning electron microscopy and the high resolution transmission electron microscopy images corroborate the formation of the nanoflake-like morphology of Cu2MnS2 with the strong interaction of rGO. The selected area electron diffraction analysis pattern reveals a polycrystalline nature. The Fourier transform infrared spectrum shows the existence of a metal sulfur vibrational band at 590 cm-1, and Raman analysis infers the presence of rGO. The X-ray photoelectron spectroscopy spectra reveal the oxidation states of the elements present in the samples. Using Brunauer-Emmett-Teller analysis, the surface area of CMS-20 is found to be 117.04 m2/g. The measured OER overpotentials using linear sweep volammetry and the values are 380, 370, 340, 376, and 400 mV at 10 mA/cm2 for CMS, CMS-10, CMS-20, CMS-30, and CMS-40, respectively, and the corresponding Tafel slope values are 179, 158, 149, 206, and 240 mV/decade, respectively. The electrochemical active surface area is estimated using cyclic voltammetry for all of the catalysts, where CMS-20 showed a larger surface area. Also, the same catalyst exhibits good stability for ∼24 h at a constant potential, which is confirmed via chronoamperometry. Thus, combining transition metal-based sulfides with carbonaceous materials indicates improved catalytic behavior for the preparation of high-performance OER electrocatalysts. Overall, the prepared CMS-20 performed as an efficient OER electrocatalyst and can be utilized for practical applications in energy conversion.

Tailoring phases of ferrihydrite/α-Fe2O3@C nanocomposites using syringyl and guaiacyl-rich biomass-derived carbon nanodots for electrochemical application

Biomass-derived carbon nanodots (CNDs) hold promise as effective reducing agents for metal oxide nanoparticles yet understanding the intricate interplay with CND structure remains challenging. This study explores the impact of lignin types, specifically syringyl (S), and guaiacyl (G) units in CNDs on metal oxide phases and their electrochemical activity toward dopamine oxidation. We design phases of ferrihydrite/α-Fe2O3@C nanocomposites, using hazelnut carbon nanodots (HS-CNDs (S-rich)) and beetroot carbon nanodots (BS-CNDs (G-rich)) via a one-pot hydrothermal technique. Our findings show S units in HS-CNDs promote α-FeOOH/α-Fe2O3@CHS, while G units in BS-CNDs favor α (β)-FeOOH/α-Fe2O3@CBS. In contrast to α(β)-FeOOH/α-Fe2O3@CBS, α-FeOOH/α-Fe2O3@CHS exhibits superior electrochemical performance in dopamine oxidation due to its larger electrochemical active surface area, higher absorbance capacity, and shortened electron transfer length. Moreover, α-FeOOH/α-Fe2O3@CHS nanocomposites demonstrate remarkable dopamine selectivity, achieving rapid detection response in 10 s with a low LOD of 4 nM within a broad linear range (0.05–0.3 μM), demonstrating impressive reproducibility (97.5 %), stability (96.4 %), and works in real-time human urine detection with a recovery rate of ranging from 94.57 % and 102.2 %. Therefore, the utilization of biomass-derived CNDs, particularly S and G units-rich CNDs, in tailoring the phases of ferrihydrite/α-Fe2O3@C nanocomposites for electrochemical dopamine detection is promising.

Advanced (Cu,Co)Se2 Nanocubes and Ti‐MXene Based Screen Printed Electrodes for High Performance Flexible Microsupercapacitors

AbstractNowadays, the demand for portable micro‐energy storage devices with high energy density and scalable printing with cost‐effective fabrication for microsupercapacitors (MSC) are essential. Furthermore, the urgent need for this high‐performance MSC to meet all industrial sector requirements are very challenging. Herein, the screen printable MSC with high energy density is demonstrated by using copper hexacyanocobaltate (CuHCCo) derived (Cu,Co)Se2 nanocubes as the positive electrode and Ti‐MXene (Ti3C2Tx) as the negative electrode. The prepared battery type (Cu,Co)Se2 nanocubes greatly enhance the high electrochemical activity and active surface area. As a result, it delivers a high specific capacity of 602 C g−1 at the current density of 1 A g−1. The fabricated screen printable asymmetric MSC has enhanced ion‐to‐electron transfer in printable microelectrodes with numerous electrochemical active sites and delivered the high areal capacitance of 58 mA cm−2 at the current density of 1 mA cm−2 with a wide potential window. The device gives a high energy density of 8.06 µWh cm−2 and a high power density of 5 mW cm−2. These results demonstrate the new strategies of fabricating electrode materials in screen printable asymmetric MSC and show promising in microscale energy storage devices in the miniaturized devices with sustainable self‐powered compatibility.

Multi-interface and rich-defects 1T phase MoS2 combine with FeS anchored on reduced graphene oxide for efficient alkaline hydrogen evolution

Exploring and fabricating noble-metal-free and cost-effective electrocatalysts to minimise the excessive potential required is of great significance for alkaline hydrogen evolution reaction (HER). Herein, we report FeS/1T-MP MoS2@rGO heterostructure with 1T and 2H mixed phase MoS2 (1T-MP MoS2) combining with FeS anchored on reduced graphene oxide (rGO) matrix, which is synthetized by utilizing Anderson polyoxometalate as Fe–Mo precursor by a facile hydrothermal method. The FeS/1T-MP MoS2@rGO heterostructure in the form of interconnected nanosheet arrays with multiple interfaces and rich-defects, which is in favor of the immersion of the electrolyte and exposing more active sites. Benefiting from the synergistic advantages of 1T-MoS2, FeS and rGO, FeS/1T-MP MoS2@rGO heterostructure delivers enhanced conductivity, enlarged electrochemical active surface area, and eventually promote the HER kinetics. As expected, FeS/1T-MP MoS2@rGO heterostructure emerges prominent HER activity with low overpotentials of 102 and 256 mV to achieve current density of 10 and 100 mA cm−2, outperforming vast majority of the advanced 1T MoS2-based alkaline HER electrocatalysts.

Building robust copper nanostructures via carbon coating derived from polydopamine for oxygen reduction reaction

This study explores the synthesis and electrocatalytic performance of copper-nitrogen-carbon composites formed by Cu single atoms/clusters embedded in nitrogen-doped carbon with Cu/Cu2O nanoparticles (Cu-X-NC) for the oxygen reduction reaction (ORR). The catalysts were synthesized using polydopamine as a carbon and nitrogen source via the solvothermal carbonization (STC) method, followed by pyrolysis and acid washing. The effect of solvothermal carbonization temperature (120, 150, and 180 ºC) on the structure and ORR activity was investigated. The physicochemical characterization showed that higher STC temperatures reduced the size of copper crystallites, slightly increased the formation of copper(I) oxide, and led to the creation of well-dispersed copper single atoms/clusters at 150°C. This optimal dispersion enhances the interaction between the copper single atoms and the reactants, leading to faster ORR kinetics, as demonstrated by the lower charge transfer resistance values in electrochemical impedance spectroscopy measurements. Additionally, the balance between micropore and mesopore structures at this temperature facilitates efficient mass transport, which is critical for achieving higher ORR activity. Moreover, accelerated stability tests showed excellent durability for Cu-150-NC, with negligible loss in onset potential after 10,000 cycles. The solvothermal process significantly increased the electrochemically active surface area (ECSA), with Cu-150-NC displaying the highest specific activity and mass activity per gram of copper, indicating superior performance. Overall, these findings underscore the importance of synthesis optimization and provide valuable insights for designing eco-friendly and high-performance copper catalysts for fuel cell applications.

Dual modification of cobalt silicate nanobelts by Co3O4 nanoparticles and phosphorization boosting oxygen evolution reaction properties

Oxygen evolution reaction (OER) process is the “bottleneck” of water splitting, and the low-cost and high-efficient OER catalysts are of great importance and attractive but they are still challenging. Herein, a dual modification strategy is developed to tune and enrich the structure of cobalt silicate (Co2SiO4) showing boosted OER properties. Cobalt oxide (Co3O4) decorated Co2SiO4 nanobelts, denoted as CS, is firstly prepared using a Co-based precursor by a facile hydrothermal reaction. Then, cobalt phosphide (CoP) nanoparticles are in-situ grown on CS (denoted as CS-P) by the phosphorization process, which provide many active sites and boost the surface reactivity. The experimental results and density function theory (DFT) calculations both reveal that the CoP on CS can improve the conductivity and ensure fast kinetics, thus leading to boost the OER properties of Co2SiO4. When the phosphorization temperature is at 400 °C (CS-P400), it gains the lowest overpotential of 297 mV, which is much lower than CS (340 mV) and Co2SiO4 (409 mV) at 10 mA·cm−2, and even superior to the state-of-the-art transition metal silicates. CS-P400 also achieves high electrochemical active surface area (ECSA) and small Tafel slope owing to its porous structures with large specific surface area and nanosheet-like structures which are good for exposing many active sites and favorable to the fast kinetics. This work not only provides a dual modification route to boost catalytic activity of Co2SiO4 (CS-P400), but also sheds light on a new avenue for developing highly dispersed CoP on silicates to boost OER performances.

Assembly and operation optimization of proton exchange membrane water electrolyzer for performance enhancement

Abstract Proton exchange membrane water electrolysis (PEMWE) for hydrogen production possesses wide-ranging and rapid dynamic response capabilities, offering promising applications in the consumption of new energy sources and the dynamic balancing of power grids with a high proportion of renewable energy. The assembly and operating conditions of PEMWE significantly affect its performance. Therefore, thoroughly studying and understanding the influence of PEMWE’s assembly and operating conditions on water electrolysis performance are crucial for enhancing PEMWE’s performance and promoting its applications. In this research, the influence of installation preload torque, feedwater flow rate, and operating temperature on the performance of the electrolyzer, including the electrochemical active specific surface area (ECSA), high-frequency resistance (HFR) and various types of polarizations (including activation polarization, ohmic polarization, and mass transfer polarization) during the operation of the electrolyzer, were detailedly investigated. The results showed that the optimal preload torque and operating temperature for the electrolyzer were 3 Nm and 80°C. Under these conditions, an optimized PEMWE performance would be achieved by ensuring that the feedwater flow rate exceeded the water consumption during electrolysis.

Development of an efficient bifunctional electrocatalyst based on Co/CoSe2 nanoparticles embedded in N, Se co-doped carbon for AEMFC and rechargeable Zn-air battery

We suggest a hollow-structured N, Se dual-doped carbon framework embedded with Co/CoSe2 nanoparticles (Co/CoSe2@NSeC) as highly efficient bifunctional electrocatalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The prepared electrocatalyst exhibits high electrochemical active surface area attributed to its unique hollow/porous structure and defective heteroatom doping sites. Furthermore, the strongly coupled heterojunction between Co and CoSe2 species not only provides abundant and highly active sites but also generates built-in electric field, thereby promoting electron transfer during the electrocatalytic reaction. Based on the above considerations, the prepared catalyst shows excellent bifunctional electrocatalytic performance. Leveraging the excellent ORR activity of Co/CoSe2@NSeC, alkaline exchange membrane fuel cells (AEMFC) with the Co/CoSe2@NSeC as air cathode exhibits high power density of 171.23 mW cm2. Furthermore, the rechargeable Zn-air battery employing the Co/CoSe2@NSeC shows high specific capacity (729.4 mAh gZn−1), peak power density (192.88 mW cm2), and sustained stability over 300 cycles.

Nanostructure-dependent colouration efficiency of electrochromic coatings using 0D, 1D, and 2D WO3 for smart windows

Towards the development of highly efficient electrochromic coatings, the crystallinity, morphology (e.g. size and shape) of electrochromic nanomaterials, and their charge insertion capacities play a significant role. Herein, we report the structure-dependent colouration effciency in electrochromic coatings based on the use of 0D, 1D and 2D tungsten trioxide (WO3) nanostructures. A series of WO3 with different nanostructures were prepared and used as working electrodes to fabricate electrochromic devices for smart windows applications. Facile spray coating was applied on fluorine-doped tin oxide (FTO) substrate to make ∼70 ​% transparent working electrodes to investigate their charge insertion capacities, electrochromic active surface area, and colouration efficiency. Results showed that the 2D WO3 nanoflakes displayed the highest diffusion coefficient for the intercalation of 1.52 ​× ​10 −10 ​cm2/s with an increased electrochemical active surface area of 25.10 ​mF/cm2, a large modulation of optical reflectance (42.63 ​%) with 3.79 ​s shorter response time for bleaching and a greater colouration efficiency (CE) value (89.29 ​cm2/C) at 700 ​nm compared to the CE value for 1D WO3 (of 22 ​cm2/C) and 0D WO3 (8 ​cm2/C). The outcome of this study provides a new insight and valuable contribution to design an efficient electrochromic coating by controlling and optimising the nanostructures of selective electrochromic materials.

High-performance porous 3D Ni skeleton electrodes for the oxygen evolution reaction

A key component of green hydrogen production technologies is the fabrication of large-scale porous transport layer (PTL) for use in anion electrolyte membrane water electrolysers (AEMWEs). One strategy to achieve that goal is to manufacture Ni-based 3D electrode skeletons that can be further catalyzed to achieve high current densities at low overpotentials. In the present work, shock-wave induced spray (SWIS) and cold spray (CS) deposition techniques were used to prepare 20 cm2 Ni-based electrode skeletons. In our experimental conditions, the porosity of coatings prepared using the SWIS deposition system and Ni powders with particle sizes D50 = 32 and 75 μm never exceeded 28%. Higher porosity could only be achieved using the CS deposition system and a spheroidal Ni–Al powder, whose particles consist of an aluminum core encapsulated in a nickel shell. After Al leaching in an alkaline solution, the resulting electrodes showed good mechanical and structural integrity with up to 41% porosity. The electrochemical active surface area of the most porous electrodes is a factor of 2100 larger than a polished Ni plate, and it has superaerophobic properties with a captive air bubble contact angle of 151°. During 1 h of electrolysis, the overpotential at 100 mA cm−2 of the most active leached Ni–Al cold spray deposited electrode was 330 mV, compared to 380 mV for a Ni foam electrode.

Trace RuO2 nanoparticles loaded nickel-coated multi-walled carbon nanotubes to boost hydrogen evolution reaction under acidic and alkaline media

Developing low-cost catalysts with high activity for the Hydrogen Evolution Reaction (HER) is a main challenge to reduce the dependence on precious metals while maintaining the catalytic activity. In this study, nickel-plated multi-walled carbon nanotubes (Ni-MWCNTs) with a large number of active sites were selected, and Ni-MWCNTs electrocatalysts loaded with trace amounts of RuO2 nanoparticles were prepared by annealing treatment, which exhibited excellent HER performances in both acidic and alkaline media. The RuO2 nanoparticles loaded nickel-coated multi-walled carbon nanotubes (RuO2@Ni-MWCNTs) had a small electrochemical impedance spectrum (EIS) and a large electrochemically active surface area (ECSA). Notably, RuO2@Ni-MWCNTs with less than 1 % Ru content exhibited excellent catalytic activities in both acidic and alkaline solutions. The results showed that the overpotentials of RuO2@Ni-MWCNTs were 20.2 mV (alkaline) and 73.7 mV (acidic), respectively. After stabilization at 20 mA cm−2 for 90 h, the evaluation results showed that RuO2@Ni-MWCNTs could maintain their catalytic efficiency without significant degradation.

Theoretical design and synthesis of Co30Ni60/CC for high selective methanol oxidation assisted energy-saving hydrogen production

The integration of methanol oxidation reaction (MOR) with hydrogen evolution reaction (HER) represents an advanced approach to hydrogen production technology. Nonetheless, the rational design and synthesis of bifunctional catalysts for both MOR and HER with exceptional activity, stability and selectivity present formidable challenges. In this work, firstly, density functional theory (DFT) was utilized to design and evaluate material models with high performance for both MOR and HER. Secondly, guided by DFT, Co30Ni60/CC (CC, carbon cloth) composites with a leaf-like nanosheet structure were successfully fabricated via electrodeposition. In the MOR process, Ni acts as the predominant active center, while Co amplifies the electrochemically active surface area (ECSA) and enhances the selectivity of methanol oxidation. Conversely, in the HER process, Co serves as the primary active center, with Ni augmenting the charge transfer rate. The electrochemical results demonstrate that Co30Ni60/CC exhibits exceptional performance in both MOR and HER at a current density (j) of 10 mA cm−2, with peak potentials of 1.323 V and −95 mV, respectively. Additionally, it shows remarkable selectivity for the oxidiation of methanol to high value-added formic acid. Thirdly, following a 100 h chronopotentiometry (CP) test, the required potential demonstrates an increase of 4.9 % (MOR) and 8.1 % (HER), signifying the superior stability of Co30Ni60/CC compared to those reported in the literature. The exceptional performance of Co30Ni60/CC can be primarily attributed to that the leaf-like nanosheets structure not only exposes a plethora of active sites but also facilitates electrolyte diffusion, the monolithic structure prepared by electrodeposition enhances its stability, and the transfer of electrons from Co to Ni regulates its electronic structure, as corroborated by X-ray photoelectron spectroscopy (XPS) and density of states (DOS) analyses. Finally, at the same j, the voltage required by the Co30Ni60/CC||Co30Ni60/CC electrolytic cell, powered by an electrochemical workstation, is 198 mV lower than that required for alkaline water-splitting. Meanwhile, at higher j (100 mA cm−2), the electrolytic cell exhibits sustained and stable operation for 150 h, enabling high-efficiency hydrogen production and the synthesis of high value-added formic acid.