Mesoporous K-doped NiCo2O4 derived from a Prussian blue analog: high-yielding synthesis and assessment as oxygen evolution reaction catalyst

The conversion and storage of clean renewable energy can be achieved using water splitting. However, water splitting exhibits sluggish kinetics because of the high overpotentials of the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) and should therefore be promoted by OER and/or HER electrocatalysts. As the kinetic barrier of the former reaction exceeds that of the latter, high-performance OER catalysts are highly sought after. Herein, K-doped NiCo₂O₄ (HK-NCO) was hydrothermally prepared from a Prussian blue analog with a metal–organic framework structure and assessed as an OER catalyst. Extensive K doping increased the number of active oxygen vacancies and changed their intrinsic properties (e.g., binding energy), thus increasing conductivity. As a result, HK-NCO exhibited a Tafel slope of 49.9 mV dec⁻¹ and a low overpotential of 292 mV at 10 mA cm⁻², outperforming a commercial OER catalyst (Ir) and thus holding great promise as a component of high-performance electrode materials for metal-oxide batteries and supercapacitors.

OER characteristics of K-doped NiCo₂O₄ catalyst and K doping control through simple hydrothermal synthesis.     

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.     

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.     

A high-efficiency oxygen evolution electrode material of a carbon material containing a NiCo bimetal

The preparation of highly efficient, stable, and low-cost electrocatalysts for the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) is still a challenge for the development of new energy systems. In this work, a NiCo bimetal loaded on porous carbon (NiCo-C/NF) grown on nickel foam (NF) was obtained via the pyrolysis of a NiCo bimetal MOF (NiCo-MOF/NF) under a nitrogen atmosphere at 500 °C. Compared with NiCo-MOF/NF, NiCo-C/NF had a larger specific surface and uniform mesoporous structure. As an electrocatalyst in the OER, this new type of electrode operated with better stability in an alkaline solution (1.0 mol L⁻¹ KOH), the overpotential when the current density reached 10 mA cm⁻² was only 260 mV, and the electrode also exhibited long-term durability in a stability test for 10 h without significant changes. The excellent activity and stability toward the OER can be attributed to the synergistic effect of the NiCo bimetal and the abundant active sites exposed after the carbonization of NiCo-MOF, which compensated for the defect of the insufficient conductivity of the material and promoted the evolution of oxygen in the catalytic process.

The preparation of highly efficient, stable, and low-cost electrocatalysts for the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) is still a challenge for the development of new energy systems.     

Controlled assembly of cobalt embedded N-doped graphene nanosheets (Co@NGr) by pyrolysis of a mixed ligand Co(ii) MOF as a sacrificial template for high-performance electrocatalysts

The development of high-efficiency and durable bifunctional electrocatalysts is an important and challenging topic in the area of energy storage/conversion. Herein, we prepared metallic cobalt nanoparticle decorated N-doped graphitic sheets (Co@NGr) by adopting facile pyrolysis of a mixed ligand cobalt-based MOF (CoMOF-2) as a sacrificial template displaying good OER and HER activity. The catalytic material harvested at three different pyrolytic temperatures was characterized by various analytical methods such as PXRD, SEM, TEM, Raman, and XPS analyses. The catalytic activity of the obtained hybrid composite materials towards oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) was studied. Co@NGr-900 was found to be an efficient bifunctional electrocatalyst and 10 mA cm⁻² current density was afforded at an overpotential of 390 mV for OER and 340 mV for HER respectively. This study provides insight for the development of cost-effective nonprecious element-based electrocatalysts for water splitting which has relevance in energy storage and conversion. Catalytic performance is governed by the synergistic compositional effect of metallic cobalt/nitrogen-doping in the graphitic carbon increasing the electrical conductivity/active sites of the composite material.

Synthesis, characterization and application of monodispersed cobalt embedded nitrogen-doped graphene derived from a cobalt-based mixed ligand MOF by pyrolysis as a bifunctional electrocatalyst for water splitting have been investigated.     

Highly dispersed ruthenium nanoparticles on nitrogen doped carbon toward efficient hydrogen evolution in both alkaline and acidic electrolytes

Efficient and inexpensive electrocatalysts toward the hydrogen evolution reaction (HER) play an important role in electrochemical water splitting. Herein, we report the synthesis of highly dispersed ruthenium nanoparticles (2.2 ± 0.4 nm) on nitrogen doped carbon (Ru/N-C) by chemical reduction of RuCl₃ on carbon in the presence of polyvinylpyrrolidone in combination with subsequent pyrolysis. Ru/N-C exhibits an excellent overpotential of 13.5 and 18.5 mV at 10 mA cm⁻² in 1.0 M KOH and 0.5 M H₂SO₄ aqueous solution, respectively, much better than and comparable to those of commercial Pt/C (38.0 and 10.0 mV). The exceptional HER activity arises from high surface area of ultrafine Ru nanoparticles and appropriate Ru electronic state tuned by nitrogen dopant. Furthermore, Ru/N-C demonstrates excellent durability in both alkaline and acidic condition relative to commercial Pt/C. We speculate that the nitrogen dopant might have coordinated with Ru and tightly anchored Ru nanoparticles, preventing them from agglomerating.

Ultrafine ruthenium nanoparticles on nitrogen doped carbon show exceptional activity toward the hydrogen evolution reaction in alkaline and acidic electrolytes.     

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.     

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.     

Boosting the hydrogen evolution reaction activity of Ru in alkaline and neutral media by accelerating water dissociation

Electrochemical water splitting via a cathodic hydrogen evolution reaction (HER) is an advanced technology for clean H₂ generation. Ru nanoparticle is a promising candidate for the state-of-the-art Pt catalyst; however, they still lack the competitiveness of Pt in alkaline and neutral media. Herein, a ternary HER electrocatalyst involving nano Ru and Cr₂O₃ as well as N-doped graphene (NG) that can work in alkaline and neutral media is proposed. Cr₂O₃ and NG feature strong binding energies for hydroxyl and hydrogen, respectively, which can accelerate the dissociation of water, whereas Ru has weak hydrogen binding energy to stimulate hydrogen coupling. The HER activity of Ru is greatly enhanced by the promoted water-dissociation effect of NG and Cr₂O₃. To achieve a current density of 10 mA cm⁻², the as-obtained Ru–Cr₂O₃/NG only needs a very low overpotential of 47 mV, which outperforms the activity of Pt/C in alkaline media. The strategy proposed here, multi-site acceleration of water dissociation, provides new guidance on the design of a highly efficient, inexpensive, and biocompatible HER catalyst in nonacidic condition.

The electrocatalytic activity of Ru in non-acidic media for hydrogen evolution reaction can be greatly boosted by Cr₂O₃ and N-doped graphene.     

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.     

Construction of hierarchical CoP@Ni2P core–shell nanoarrays for efficient electrocatalytic hydrogen evolution in alkaline solution

Design and synthesis of non-noble electrocatalyst with controlled structure and composition for hydrogen evolution reaction (HER) are significant for large-scale water electrolysis. Here, an elegant multi-step templating strategy is developed for the fabrication of vertically aligned CoP@Ni₂P nanowire–nanosheet architecture on Ni foam. Cobalt–carbonate hydroxides nanowires grown on Ni foam are first synthesized as the self-template. Afterward, a layer of amorphous Ni(OH)₂ nanosheets is grown on the Co-based precursors through a chemical bath process, which is then transformed into the hierarchical CoP@Ni₂P nanoarrays by a co-phosphatization treatment. Owing to the synergistic effect of the compositions and the advantages of the hierarchical heterostructures, the resulting hybrid electrocatalyst with dense heterointerfaces is revealed as an excellent HER catalyst, with a low overpotential of 101 mV at the current density of 10 mA cm⁻², a relatively small Tafel slope of 79 mV dec⁻¹, and favorable long-term stability of at least 20 h in 1 M KOH.

Benefiting from their structural and compositional merits, the as-synthesized CoP@Ni₂P core–shell nanoarrays exhibit excellent electrocatalytic activity and long-term stability for HER in 1 M KOH.     

RuxSe@MoS2 hybrid as a highly efficient electrocatalyst toward hydrogen evolution reaction

Alkaline hydrogen evolution reaction (HER) requires highly efficient and stable catalytic materials, the engineering of which needs overall consideration of the water dissociation process as well as the intermediate hydrogen adsorption process. Herein, a Ru_xSe@MoS₂ hybrid catalyst was synthesized by the decoration of MoS₂ with Ru_xSe nanoparticles through a two-step hydrothermal reaction. Due to the bifunctionality mechanism in which Ru promotes the water dissociation and the nearby Se atoms, unsaturated Mo and/or S atoms act as active sites for the intermediate hydrogen adsorption, the hybrid catalyst exhibits an exceptional HER performance in basic media with a rather low overpotential of 45 mV at a current density of 10 mA cm⁻² and a small Tafel slope of 42.9 mV dec⁻¹. The synergetic effect between Ru_xSe and MoS₂ not only enables more catalytically active sites, but also increases the inherent conductivity of the hybrid catalyst, leading to more favorable HER kinetics under both alkaline and acidic conditions. As a result, Ru_xSe@MoS₂ also demonstrates an enhanced catalytic activity toward HER in 0.5 M H₂SO₄ in comparison with pure Ru_xSe and MoS₂, which requires an overpotential of 120 mV to deliver a 10 mA cm⁻² current density and gives a Tafel slope of 72.2 mV dec⁻¹. In addition, the hybrid electrocatalyst also exhibits superior electrochemical stability during the long-term HER process in both acidic media and alkaline media.

The bifunctionality mechanism of Ru_xSe@MoS₂ greatly enhances the alkaline HER performance, in which Ru promotes water dissociation and the nearby Se atoms, unsaturated Mo and/or S atoms act as active sites for the intermediate hydrogen adsorption.     

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.     

Spinel oxide CoFe2O4 grown on Ni foam as an efficient electrocatalyst for oxygen evolution reaction

The effect of the oxygen evolution reaction (OER) is important in water splitting. In this work, we develop sphere-like morphology spinel oxide CoFe₂O₄/NF by hydrothermal reaction and calcination, and the diameter of the spheres is about 111.1 nm. The CoFe₂O₄/NF catalyst exhibits excellent electrocatalytic performance with an overpotential of 273 mV at a current density of 10 mA cm⁻² and a Tafel slope of 78 mV dec⁻¹. The cycling stability of CoFe₂O₄/NF is remarkable, and it only increased by 5 mV at a current density of 100 mA cm⁻² after 3000 cycles. Therefore, this simple method to prepare CoFe₂O₄/NF can enhance the OER properties of electrocatalysts, which makes CoFe₂O₄/NF a promising material to replace noble metal-based catalysts for the oxygen evolution reaction.

The effect of the oxygen evolution reaction (OER) is important in water splitting.     

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.     

Interfacial configuration of heterogeneous NiFe–sulfide as a highly electrocatalytic selective oxygen evolution reaction electrode toward seawater electrolysis

Seawater electrolysis for scalable hydrogen generation has attracted much attention due to the abundance of seawater in nature. However, it is severely impeded by the chlorine ions in seawater, which can cause corrosion and an undesirable competing reaction at the anode. So it is highly desirable to exploit a highly active, chlorine corrosion resistant and selective OER electrode for seawater splitting. Here, a heterogeneous NiFe–sulfide electrode is proposed to achieve an efficient OER process in alkaline seawater. Considering the 2D lamellar architecture with a rough surface and a considerable amount of micro voids, the dual electronic configuration of sulfur and iron, the strong synergistic effect between Ni and Fe at the atomic level and the interfacial engineering between the NiS/Ni₃S₂ phase and FeS phase at the nanoscale level, the Ni₆Fe₂S-0.05 M electrode exhibits predominant catalytic activity with an overpotential of 353 mV to reach 200 mA cm⁻², superior long-term stability with 50 h accelerated stability test and higher selectivity toward the OER.

The Ni_xFe_yS/CH-z M electrode with rough surface and micro voids was prepared. Dual-doping can generate interfacial engineering between multiple heterogeneous phases. Electronic regulation and geometrical construction can boost seawater electrolysis.     

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.     

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.     

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.