Enhancing the water splitting performance via decorating Co3O4 nanoarrays with ruthenium doping and phosphorization

Hydrogen is the most promising renewable energy source to replace traditional fossil fuels for its ultrahigh energy density, abundance and environmental friendliness. Generating hydrogen by water splitting with highly efficient electrocatalysts is a feasible route to meet current and future energy demand. Herein, the effects of Ru doping and phosphorization treatment on Co₃O₄ nanoarrays for water splitting are systemically investigated. The results show that a small amount of phosphorus can accelerate hydrogen evolution reaction (HER) and the trace of Ru dopant can significantly enhance the catalytic activities for HER and oxygen evolution reaction (OER). Ru-doped cobalt phosphorous oxide/nickel foam (CoRuPO/NF) nanoarrays exhibit highly efficient catalytic performance with an overpotential of 26 mV at 10 mA cm⁻² for HER and 342 mV at 50 mA cm⁻² for OER in 1 M KOH solution, indicating superior water splitting performance. Furthermore, the CoRuPO/NF also exhibits eminent and durable activities for alkaline seawater electrolysis. This work significantly advances the development of seawater splitting for hydrogen generation.

CoRuPO/NF shows low overpotentials in HER and OER.     

Nickel foam and stainless steel mesh as electrocatalysts for hydrogen evolution reaction,oxygen evolution reaction and overall water splitting in alkaline media

In this work, several commonly used conductive substrates as electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) under alkaline conditions were studied, including nickel foam (Ni foam), copper foam (Cu foam), nickel mesh (Ni mesh) and stainless steel mesh (SS mesh). Ni foam and SS mesh are demonstrated as high-performance and stable electrocatalysts for HER and OER, respectively. For HER, Ni foam exhibited an overpotential of 0.217 V at a current density of 10 mA cm⁻² with a Tafel slope of 130 mV dec⁻¹, which were larger than that of the commercial Pt/C catalyst, but smaller than that of the other conductive substrates. Meanwhile, the SS mesh showed the best electrocatalytic performance for OER with an overpotential of 0.277 V at a current density of 10 mA cm⁻² and a Tafel slope of 51 mV dec⁻¹. Its electrocatalytic performance not only exceeded those of the other conductive substrates but also the commercial RuO₂ catalyst. Moreover, both Ni foam and SS mesh exhibited high stability during HER and OER, respectively. Furthermore, in the two-electrode system with Ni foam used as the cathode and SS mesh used as the anode, they enable a current density of 10 mA cm⁻² at a small cell voltage of 1.74 V. This value is comparable to or exceeding the values of previously reported electrocatalysts for overall water splitting. In addition, NiO on the surface of Ni foam may be the real active species for HER, NiO and FeO_x on the surface of SS mesh may be the active species for OER. The abundant and commercial availability, long-term stability and low-cost property of nickel foam and stainless steel mesh enable their large-scale practical application in water splitting.

Efficient electrocatalytic overall water splitting is achieved with commercially-available and low-cost nickel foam and stainless steel mesh as cathode and anode electrodes.     

In situ addition of graphitic carbon into a NiCo2O4/CoO composite: enhanced catalysis toward the oxygen evolution reaction

We present a rapid, environmentally benign one-pot synthesis technique for the production of a NiCo₂O₄/CoO and graphite composite that demonstrates efficient electrocatalysis towards the Oxygen Evolution Reaction (OER), in 1.0 M KOH. The NiCo₂O₄/CoO/graphitic carbon composite that displayed optimal OER catalysis was synthesized by nitrate decomposition in the presence of citric acid (synthesized glycine and sucrose variants displayed inferior electro kinetics towards the OER). Screen-printed electrodes modified with ca. 530 μg cm⁻² of the citric acid NiCo₂O₄/CoO/graphite variant displayed remarkable OER catalysis with an overpotential (η) of +323 mV (vs. RHE) (recorded at 10 mA cm⁻²), which is superior to that of IrO₂ (340 mV) and RuO₂ (350 mV). The composite also exhibited a large achievable current density of 77 mA cm⁻² (at +1.5 V (vs. RHE)), a high O₂ turnover frequency of 1.53 × 10⁻² s⁻¹ and good stability over the course of 500 repeat cycles. Clearly, the NiCo₂O₄/CoO composite has the potential to replace precious metal based catalysts as the anodic material within electrolysers, thereby providing a reduction in the associated costs of hydrogen production via water splitting.

A facile synthesis technique for the production of NiCo₂O₄/CoO and graphite composites that demonstrate efficient electrocatalysis towards the oxygen evolution reaction.     

Electrochemical oxidation of boron-doped nickel–iron layered double hydroxide for facile charge transfer in oxygen evolution electrocatalysts

The oxygen evolution reaction (OER) is the key reaction in water splitting systems, but compared with the hydrogen evolution reaction (HER), the OER exhibits slow reaction kinetics. In this work, boron doping into nickel–iron layered double hydroxide (NiFe LDH) was evaluated for the enhancement of OER electrocatalytic activity. To fabricate boron-doped NiFe LDH (B:NiFe LDH), gaseous boronization, a gas–solid reaction between boron gas and NiFe LDH, was conducted at a relatively low temperature. Subsequently, catalyst activation was performed through electrochemical oxidation for maximization of boron doping and improved OER performance. As a result, it was possible to obtain a remarkably reduced overpotential of 229 mV at 10 mA cm⁻² compared to that of pristine NiFe LDH (315 mV) due to the effect of facile charge-transfer resistance by boron doping and improved active sites by electrochemical oxidation.

An electrochemically oxidized boron-doped NiFe LDH electrocatalyst was prepared and the electrocatalyst showed improved water oxidation performance.     

Ultradispersed IrxNi clusters as bifunctional electrocatalysts for high-efficiency water splitting in acid electrolytes

Design and synthesis of electrocatalysts with high activity and low cost is an important challenge for water splitting. We report a rapid and facile synthetic route to obtain Ir_xNi clusters via polyol reduction. The Ir_xNi clusters show excellent activity for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in acidic electrolytes. The optimized Ir₂Ni/C clusters exhibit an electrochemical active area of 18.27 mF cm⁻², with the overpotential of OER being 292 mV and HER being 30 mV at 10 mA cm⁻², respectively. In addition, the Ir₂Ni/C used as the cathode and anode for the H-type hydrolysis tank only needs 1.597 V cell voltages. The excellent electrocatalytic performance is mainly attributed to the synergistic effect between the metals and the ultra-fine particle size. This study provides a novel strategy that has a broad application for water splitting.

A method of preparing Ir_xNi/C clusters by polyol reduction using a XC-72R support was proposed. Due to the 2 nm size of the catalyst particles, more active sites are exposed. This is a promising route for the development of efficient water splitting electrocatalysts.     

Ni foam electrode solution impregnated with Ni-FeX(OH)Y catalysts for efficient oxygen evolution reaction in alkaline electrolyzers

Oxygen evolution reaction (OER) is a demanding step within the water splitting process for its requirement of a high overpotential. Thus, to overcome this unfavourable kinetics, an efficient catalyst is required to expedite the process. In this context, we report on Ni foam functionalised with low cost iron (Fe) and iron hydroxide (Fe(OH)_X), wet chemically synthesized as OER catalysts. The prepared catalyst based on iron hydroxide precipitate shows a promising performance, exhibiting an overpotential of 270 mV (at a current density of 10 mA cm⁻² in 1 M KOH solution), an efficient Tafel slope of ∼50 mV dec⁻¹ and stable chronopotentiometry. The promising performance of the anode was further reproduced in the overall water splitting reaction with a two electrode cell. The overall reaction requires a lower potential of 1.508 V to afford 10 mA cm⁻², corresponding to 81.5% electrical to fuel efficiency.

Modification of Ni foam electrode by FeCl₃·6H₂O and HCl, towards superior oxygen-evolving electrocatalyst for water splitting process.     

NaBH4 induces a high ratio of Ni3+/Ni2+ boosting OER activity of the NiFe LDH electrocatalyst

Electrochemical water splitting is a promising way to produce hydrogen gas, but the sluggish kinetics of the oxygen evolution reaction (OER) extremely restrict the overall conversion efficiency of water splitting. Transition metal based LDHs (TM LDHs) are one of the most effective non-noble metal OER catalysts and have attracted wide interest, especially the nickel–iron LDH (NiFe LDH). The high valence Ni³⁺ species with a large coordination number play a vital role in OER catalysis. Herein, we report on a surprising discovery that reaction between NiFe LDH and NaBH₄ with multi-hydrides induces vacancy formation around Fe³⁺ and enrichment in Ni³⁺, crucially activating the OER performance. The ratio of Ni³⁺/Ni²⁺ is found to be closely tied to the OER performance, nicely accounting for the leading role of Ni³⁺ ions in octahedral sites in electrocatalysis. Significantly, the NaBH₄ treated NiFe LDH directly on nickel foam (NF), denoted as NaBH₄–NiFe LDH@NF exhibited an outstanding OER performance with an overpotential of only 310 mV at 100 mA cm⁻², and a Tafel slope of 47 mV dec⁻¹. For the series of TM LDHs we studied with different metal combinations, the high valence metal ion is found to be positively related to OER performance.

Reaction between NiFe LDH and NaBH₄ induces vacancies around Fe³⁺ and enrichment in Ni³⁺, crucially activating the OER catalyst leading to high performance.     

Solution-phase phosphorus substitution for enhanced oxygen evolution reaction in Cu2WS4

Transition metal phosphides are among the most promising materials for achieving efficient electrocatalytic performance without the use of rare or expensive noble metals. However, previous research into phosphides for the hydrogen evolution reaction (HER) or oxygen evolution reaction (OER) has focused on high-temperature vapor-phase processes, which are not practical for large-scale applications. Here, we introduce a simple, one-step solution-phase method of phosphide synthesis by modifying Cu₂WS₄ using triphenylphosphine (TPP), which serves to substitute S with P and transform the normally inactive basal plane of Cu₂WS₄ into a defect-rich, activated basal plane. The OER activity was significantly enhanced by phosphorus substitution, with the resulting Tafel slope of the sample with ∼8 at% phosphorus reaching 194 mV dec⁻¹, a result close to that of the best OER catalyst (RuO₂, 151 mV dec⁻¹). The sample possessed stable OER performance, showing no degradation in current density over ∼24 hours (500 cycles), proving the robust and stable nature of the phosphorus substitution. These results open the possibility for further phosphide catalyst development using this low-cost, solution-phase method.

Solution-phase synthesis of a transition metal phosphide for use as a highly efficient electrocatalyst.     

Low-cost CoFe2O4/biomass carbon hybrid from metal-enriched sulfate reducing bacteria as an electrocatalyst for water oxidation

The development of electrocatalysts for the Oxygen Evolution Reaction (OER) requires extensive and challenging research for the water splitting and fuel cell applications. Herein, we report a low-cost CoFe₂O₄/biomass carbon (CFO@BC/Zn) hybrid from Co-enriched Sulfate Reducing Bacteria (Co-SRB) as an electrocatalyst for OER. The electrocatalyst exhibits a low potential of 1.53 V at a current density 10 mA cm⁻² and Tafel slope of 86 mV dec⁻¹. This method does not require high-cost or long periods of preparation. The density-functional theory (DFT) calculations show a small barrier for oxygen conversion on Fe³⁺ of CFO (100) surface. The synthesis of CFO@BC/Zn may be a new approach for obtaining low-priced electrocatalysts for OER.

A low-cost CoFe₂O₄/biomass carbon (CFO@BC/Zn) hybrid from Co-enriched Sulfate Reducing Bacteria (Co-SRB) as an electrocatalyst for OER. The electrocatalyst exhibits a low potential of 1.53 V at a current density 10 mA cm⁻² and Tafel slope of 86 mV dec⁻¹.     

Fe3+ in a tetrahedral position determined the electrocatalytic properties in FeMn2O4

As an electrocatalyst for the oxygen evolution reaction (OER) for water decomposition purposes, spinel ferrite materials have gained a lot of attention from many researchers. Herein, we document a co-precipitation synthesis of antitypical spinel nanoparticles (FeMn₂O₄) by post-annealing at different temperatures to enable modulation of the cationic oxidation state and tuning of the conversion degree for efficient and good OER performance. The electrocatalytic activity test shows that the sample annealed at 500 °C has the most optimal catalytic activity with an overpotential of 360 mV at a current density of 10 mA cm⁻² and a Tafel slope as low as 105.32 mV dec⁻¹. The formation of FeOOH during in situ OER promotes the catalytic activity of the catalysts. More importantly, according to the results of Brunauer–Emmett–Teller normalization, we demonstrate that the activity of the catalyst is also inseparable from the internal crystal structure. This work broadens the field of research on the electrocatalysis of spinel manganese ferrites.

Inspired by the flexibility of cation exchange and valence state variation in spinel ferrite, a high activity OER catalyst FeMn₂O₄ has been observed without inducing the change of composition, morphology, and atomic doping.     

Tuning composition of CuCo2S4–NiCo2S4 solid solutions via solvent-less pyrolysis of molecular precursors for efficient supercapacitance and water splitting

Mixed metal sulfides are increasingly being investigated because of their prospective applications for electrochemical energy storage and conversion. Their high electronic conductivity and high density of redox sites result in significant improvement of their electrochemical properties. Herein, the composition-dependent supercapacitive and water splitting performance of a series of Ni_(1−x)Cu_xCo₂S₄ (0.2 ≤ x ≤ 0.8) solid solutions prepared via solvent-less pyrolysis of a mixture of respective metal ethyl xanthate precursors is reported. The use of xanthate precursors resulted in the formation of surface clean nanomaterials at low-temperature. Their structural, compositional, and morphological features were examined by p-XRD, SEM, and EDX analyses. Both supercapacitive and electrocatalytic (HER, OER) properties of the synthesized materials significantly vary with composition (Ni/Cu molar content). However, the optimal composition depends on the application. The highest specific capacitance of 770 F g⁻¹ at a current density of 1 A g⁻¹ was achieved for Ni_0.6Cu_0.4Co₂S₄ (NCCS-2). This electrode exhibits capacitance retention (C_R) of 67% at 30 A g⁻¹, which is higher than that observed for pristine NiCo₂S₄ (838 F g⁻¹ at 1 A g⁻¹, 47% C_R at 30 A g⁻¹). On the contrary, Ni_0.4Cu_0.6Co₂S₄ (NCCS-3) exhibits the lowest overpotential of 124 mV to deliver a current density of 10 mA cm⁻². Finally, the best OER activity with an overpotential of 268 mV at 10 mA cm⁻² was displayed by Ni_0.8Cu_0.2Co₂S₄ (NCCS-1). The prepared electrodes exhibit high stability, as well as durability.

A multi-component CuCo₂S₄ and NiCo₂S₄ thiospinel solid solution is prepared over an entire range by a low-temperature solvent-less route. The synergistic effect from both thiospinels on water splitting and capacitance is studied.     

Ultrafine Co3O4 nanolayer-shelled CoWP nanowire array: a bifunctional electrocatalyst for overall water splitting

The development of bifunctional electrocatalysts based on highly efficient non-noble metals is pivotal for overall water splitting. Here, a composite electrode of Co₃O₄@CoWP is synthesized, where an ultrathin layer composed of Co₃O₄ nanoparticles is grown on CoWP nanowires supported on a carbon cloth (CC). The Co₃O₄@CoWP/CC electrode exhibits excellent electrocatalytic activity and improved kinetics towards both the oxygen and hydrogen evolution reactions (OER and HER). The Co₃O₄@CoWP/CC electrode achieves a current density of 10 mA cm⁻² at a low overpotential of 269 mV for the OER and −10 mA cm⁻² at 118 mV for the HER in 1.0 M KOH solution. The voltage applied to a two-electrode water electrolyzer for overall water splitting, while employing the Co₃O₄@CoWP/CC electrode as both an anode and a cathode, in order to reach a current density of 10 mA cm⁻², is 1.61 V, which is better than that for the majority of reported non-noble electrocatalysts. Moreover, the Co₃O₄@CoWP/CC electrode exhibits good stability over 24 h with slight attenuation. The electrode benefits from the enhanced adsorption of oxygen intermediates on Co₃O₄ during the OER, the increased ability for water dissociation and the optimized H adsorption/desorption ability of CoWP nanowires during the HER. This study provides a feasible approach for cost-effective and high-performance non-noble metal bifunctional catalysts for overall water electrolysis.

A hierarchical 3D self-supporting CoWP nanowire array shelled with an ultrathin Co₃O₄ nanolayer on carbon cloth (Co₃O₄@CoWP/CC) exhibits superior overall water electrolysis capability.     

Nanostructured RuO2–Co3O4@RuCo-EO with low Ru loading as a high-efficiency electrochemical oxygen evolution catalyst

Electrochemical water splitting technology is considered to be the most reliable method for converting renewable energy such as wind and solar energy into hydrogen. Here, a nanostructured RuO₂/Co₃O₄–RuCo-EO electrode is designed via magnetron sputtering combined with electrochemical oxidation for the oxygen evolution reaction (OER) in an alkaline medium. The optimized RuO₂/Co₃O₄–RuCo-EO electrode with a Ru loading of 0.064 mg cm⁻² exhibits excellent electrocatalytic performance with a low overpotential of 220 mV at the current density of 10 mA cm⁻² and a low Tafel slope of 59.9 mV dec⁻¹ for the OER. Compared with RuO₂ prepared by thermal decomposition, its overpotential is reduced by 82 mV. Meanwhile, compared with RuO₂ prepared by magnetron sputtering, the overpotential is also reduced by 74 mV. Furthermore, compared with the RuO₂/Ru with core–shell structure (η = 244 mV), the overpotential is still decreased by 24 mV. Therefore, the RuO₂/Co₃O₄–RuCo-EO electrode has excellent OER activity. There are two reasons for the improvement of the OER activity. On the one hand, the core–shell structure is conducive to electron transport, and on the other hand, the addition of Co adjusts the electronic structure of Ru.

The optimized RuO₂/Co₃O₄–RuCo-EO electrode with Ru loading of 0.064 mg cm⁻² exhibits the excellent oxygen evolution activity with an overpotential of 220 mV at the current density of 10 mA cm⁻² and a Tafel slope of 59.9 mV dec⁻¹.     

Rational construction of free-standing P-doped Fe2O3 nanowire arrays as highly effective electrocatalyst for overall water splitting

Designing electrode structures with high activity is very significant for energy conversion systems. However, single electrode materials often exhibit poor electronic transportation. To address this issue, we prepared P-Fe₂O₃ nanowire arrays through a convenient hydrothermal and phosphation method. The as-obtained electrode materials exhibited excellent electrocatalytic performance, which could be attributed to the P element decoration improving the reaction active sites. The as-obtained P-Fe₂O₃-0.45 nanowire arrays exhibited excellent OER activity with a low overpotential of 270 mV at 10 mA cm⁻² (72.1 mV dec⁻¹), excellent HER performance with a low overpotential of 126.4 mV at −10 mA cm⁻², a small Tafel slope of 72.5 mV dec⁻¹ and long durability. At the same time, the P-Fe₂O₃-0.45 nanowire arrays possessed a low cell voltage of 1.56 V at 10 mA cm⁻².

Designing electrode structures with high activity is very significant for energy conversion systems.     

Low temperature scalable synthetic approach enabling high bifunctional electrocatalytic performance of NiCo2S4 and CuCo2S4 thiospinels

Ternary metal sulfides are currently in the spotlight as promising electroactive materials for high-performance energy storage and/or conversion technologies. Extensive research on metal sulfides has indicated that, amongst other factors, the electrochemical properties of the materials are strongly influenced by the synthetic protocol employed. Herein, we report the electrochemical performance of uncapped NiCo₂S₄ and CuCo₂S₄ ternary systems prepared via solventless thermolysis of the respective metal ethyl xanthate precursors at 200 and 300 °C. The structural, morphological and compositional properties of the synthesized nanoparticles were examined by powder X-ray diffraction (p-XRD), transmission electron microscopy (TEM), high-resolution TEM, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX) techniques. Electrochemical studies indicate that NiCo₂S₄ nanoparticles synthesized at 300 °C exhibit superior energy storage characteristics with a high specific capacitance of ca. 2650 F g⁻¹ at 1 mV s⁻¹, as compared to CuCo₂S₄ nanoparticles, which showcased a specific capacitance of ca. 1700 F g⁻¹ at the same scan rate. At a current density of 0.5 A g⁻¹, NiCo₂S₄ and CuCo₂S₄ nanoparticles displayed specific capacitances of 1201 and 475 F g⁻¹, respectively. In contrast, CuCo₂S₄ nanoparticles presented a higher electrocatalytic activity with low overpotentials of 269 mV for oxygen evolution reaction (OER), and 224 mV for the hydrogen evolution reaction (HER), at 10 mA cm⁻². The stability of the catalysts was examined for 2000 cycles in which a negligible change in both OER and HER activities was observed.

A scalable solventless approach is employed to prepare NiCo₂S₄ and CuCo₂S₄ with bare surface for enhanced supercapacitance and water splitting. The particles exhibit good energy storage and electrocatalytic activity as well as stability.     

Hierarchical NiCo2O4/NiFe/Pt heterostructures supported on nickel foam as bifunctional electrocatalysts for efficient oxygen/hydrogen production

As the demand for clean and renewable energy increases, high-efficiency multifunctional electrocatalysts for water cracking have become a research hotspot. In this study, a NiCo₂O₄/NiFe/Pt composite with a hierarchical structure was successfully constructed by combining a hydrothermal growth and electrodeposition method with nickel foam as the scaffold material, and its overall water cracking reaction was studied. The laminar-structured NiCo₂O₄/NiFe composite exhibits an improved number of electrochemically active sites and shorter electron transport pathways, while the Pt particles deposited on the NiCo₂O₄/NiFe composite are conducive to improve the hydrogen evolution reaction without affecting the efficiency of the oxygen evolution reaction of the intrinsic material. The NiCo₂O₄/NiFe/Pt composite shows an excellent overall water cracking performance under alkaline conditions with a current density of 10 mA cm⁻² at an applied potential of 1.45 V, indicating a promising research prospect.

(a) LSV of overall water splitting for the respective component at a scan rate of 5 mV s⁻¹. (b) Chronopotentiometry curve under a constant current density of 20 mA cm⁻². Inset: photographic image of two-electrode water electrolysis device.     

NiCoP–CeO2 composites for efficient electrochemical oxygen evolution

In this study, a novel NiCoP–CeO₂ composite was constructed on a Ni foam by a simple hydrothermal method and thermal phosphating strategy. In the OER test, NiCoP–CeO₂ exhibited a low overpotential of 217 mV at 10 mA cm⁻², 45 mV dec⁻¹ of Tafel slopes. With the help of theoretical calculations and experimental characterization, the reason for performance improvement was analyzed in depth. The results show that CeO₂ leads to a confinement effect, maintaining the nanosheet morphology of NiCo-LDHs, which contributes to sustaining the catalyst in favourable contact with H₂O and minimizing the OER potential. Furthermore, by loading CeO₂ onto NiCoP, the hydrophilicity of the catalyst is significantly enhanced. Our work provides an ingenious synthesis strategy for the preparation of efficient and inexpensive electrocatalytic materials.

A NiCoP–CeO₂ composite was constructed by a simple hydrothermal method and thermal phosphating strategy. Benefiting from the confinement effect and optimized H₂O adsorption ability, NiCoP–CeO₂ exhibits superior OER performance than NiCoP.     

Phyto-inspired and scalable approach for the synthesis of PdO–2Mn2O3: a nano-material for application in water splitting electro-catalysis

A modified co-precipitation method has been used for the synthesis of a PdO–2Mn₂O₃ nanocomposite as an efficient electrode material for the electro-catalytic oxygen evolution (OER) and hydrogen evolution reaction (HER). Palladium acetate and manganese acetate in molar ratio 1 : 4 were dissolved in water, and 10 ml of an aqueous solution of phyto-compounds was slowly added until completion of precipitation. The filtered and dried precipitates were then calcined at 450 °C to obtain a blackish brown colored mixture of PdO–2Mn₂O₃ nanocomposite. These particles were analyzed by ultra violet visible spectrophotometry (UV-vis), infrared spectroscopy (FTIR), powder X-ray diffractometry (XRD), scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) for crystallinity, optical properties, and compositional and morphological makeup. Using Tauc''s plot, the direct band gap (3.18 eV) was calculated from the absorption spectra. The average crystallite sizes, as calculated from the XRD, were found to be 15 and 14.55 nm for PdO and Mn₂O₃, respectively. A slurry of the phyto-fabricated PdO–2Mn₂O₃ powder was deposited on Ni-foam and tested for electro-catalytic water splitting studies in 1 M KOH solution. The electrode showed excellent OER and HER performance with low over-potential (0.35 V and 121 mV) and Tafel slopes of 115 mV dec⁻¹ and 219 mV dec⁻¹, respectively. The outcomes obtained from this study provide a direction for the fabrication of a cost-effective mixed metal oxide based electro-catalyst via an environmentally benign synthesis approach for the generation of clean energy.

A modified co-precipitation method has been used for the synthesis of PdO–2Mn₂O₃ nanocomposite as an efficient electrode material for the electro-catalytic oxygen evolution (OER) and hydrogen evolution reaction (HER).     

Nitrogen and sulfur-codoped porous carbon derived from a BSA/ionic liquid polymer complex: multifunctional electrode materials for water splitting and supercapacitors

Bovine serum albumin (BSA) was complexed with a hydrophobic ionic liquid polymer (PIL) via electrostatic interaction to fabricate a carbon precursor. Then, a novel nitrogen (N) and sulfur (S) codoped micro-/mesoporous carbon (NSPC) was obtained via direct carbonization of the interpolyelectrolyte BSA@PIL complex. The newly developed NSPC materials exhibited excellent HER/OER electrocatalytic activity and stability, as well as outstanding capacitance performance. Remarkably, NSPC pyrolyzed at 1000 degrees (NSPC-1000) presented an overpotential as low as 172 mV vs. RHE (without iR correction) to achieve a current density of 10 mA cm⁻² and a Tafel slope of 44.3 mV dec⁻¹ in 0.5 M H₂SO₄ for HER, as well as a low overpotential of 460 mV vs. RHE in 0.1 M KOH for OER. Furthermore, NSPC-1000 offers a specific capacitance as high as 495 F g⁻¹ at a current density of 0.1 A g⁻¹. Such excellent performance of NSPC in electrocatalytic water splitting and supercapacitors originates from the synergistic effects of its N/S-codoping and micro-/mesoporous hierarchical architecture. Our facile protocol through combining biomacromolecules and synthetic polymers offers a new strategy in the development of effective, readily scalable and metal-free heteroatom-doped carbon materials for energy-related applications.

Nitrogen and sulfur codoped porous carbon (NSPC) is fabricated via pyrolyzing BSA and poly(ionic liquid) complex. NSPC is demonstrated to be excellent metal-free electrocatalyst for water splitting and electrode material for supercapacitor.     

Highly-dispersed ruthenium precursors via a self-assembly-assisted synthesis of uniform ruthenium nanoparticles for superior hydrogen evolution reaction

For the first time, highly-dispersed ruthenium precursors via a hydrogen-bond-driven melamine–cyanuric acid supramolecular complex (denoted CAM) self-assembly-assisted synthesis of uniform ruthenium nanoparticles with superior HER performance under both acidic and alkaline conditions are reported. Electrochemical tests reveal that when the current density is −10 mA cm⁻², the optimal Ru/CNO electrocatalyst could express low overpotentials of −18 mV and −46 mV, low Tafel slopes of 46 mV dec⁻¹ and 100 mV dec⁻¹, in 0.5 M H₂SO₄ and 1.0 M KOH, respectively. The remarkable HER performance could be attributed to uniform ruthenium with the aid of highly dispersed ruthenium precursors (Ru–CAM) and subsequent annealing results in uniform ruthenium nanoparticles.

Highly dispersed ruthenium precursors via a supramolecular self-assembly assisted synthesis of uniform ruthenium nanoparticles with excellent HER performance.