Search

Highlights: Plasma-assisted phosphorization has been used to prepare defect-rich metal phosphides. The p-NiCoP/NCF@CC shows high activities and excellent stability for the hydrogen evolution reaction and the oxygen evolution reaction. The p-NiCoP/NCF@CC shows great potential for overall water splitting. This work reports the use of defect engineering and carbon supporting to achieve metal-doped phosphides with high activities and stabilities for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in alkaline media. Specifically, the nitrogen-doped carbon nanofiber-supported Ni-doped CoP3 with rich P defects (Pv·) on the carbon cloth (p-NiCoP/NCFs@CC) is synthesized through a plasma-assisted phosphorization method. The p-NiCoP/NCFs@CC is an efficient and stable catalyst for the HER and the OER. It only needs overpotentials of 107 and 306 mV to drive 100 mA cm−2 for the HER and the OER, respectively. Its catalytic activities are higher than those of other catalysts reported recently. The high activities of the p-NiCoP/NCFs@CC mainly arise from its peculiar structural features. The density functional theory calculation indicates that the Pv· richness, the Ni doping, and the carbon supporting can optimize the adsorption of the H atoms at the catalyst surface and promote the strong electronic couplings between the carbon nanofiber-supported p-NiCoP with the surface oxide layer formed during the OER process. This gives the p-NiCoP/NCFs@CC with the high activities for the HER and the OER. When used in alkaline water electrolyzers, the p-NiCoP/NCFs@CC shows the superior activity and excellent stability for overall water splitting. [ABSTRACT FROM AUTHOR]

Developing acid‐stable electrocatalysts with high activity for the oxygen evolution reaction (OER) is of paramount importance for many energy‐related technologies. This work reports that ultrathin nitrogen‐doped carbon coated oxygen‐vacancy (Vo·) rich RuO2 nanoparticles on carbon nanotubes (CNTs) (NC@Vo·‐RuO2/CNTs‐350), synthesized through the controlled calcination in air, is an efficient acid‐stable electrocatalyst for the OER. It only needs an overpotential of 170.0 mV to drive 10.0 mA cm−2 and shows excellent stability with no distinguishable activity loss observed for >900 h. Its mass activity is >110 times higher than the commercial RuO2. In particular, an electrolyzer assembled with this catalyst shows a record‐low cell voltage of 1.45 V to deliver 10.0 mA cm−2 and exhibits a low performance drop for >1000 h. The NC@Vo·‐RuO2/CNTs‐350 also shows super‐high catalytic activities and excellent stabilities for OER in neutral and alkaline media. DFT calculations indicate that its high catalytic activity mainly arises from the strong electronic coupling between RuO2 and NC/CNTs, which increases the oxidation state and catalytic activity of Ru at the active site and improves the stabilities of lattice oxygen and surface Ru during the OER processes. The presence of Vo· can strengthen the electronic coupling between RuO2 and NC/CNTs. [ABSTRACT FROM AUTHOR]

This work reports a novel approach for the synthesis of FeCo alloy nanoparticles (NPs) embedded in the N,P‐codoped carbon coated nitrogen‐doped carbon nanotubes (NPC/FeCo@NCNTs). Specifically, the synthesis of NCNT is achieved by the calcination of graphene oxide‐coated polystyrene spheres with Fe3+, Co2+ and melamine adsorbed, during which graphene oxide is transformed into carbon nanotubes and simultaneously nitrogen is doped into the graphitic structure. The NPC/FeCo@NCNT is demonstrated to be an efficient and durable bifunctional catalyst for oxygen evolution (OER) and oxygen reduction reaction (ORR). It only needs an overpotential of 339.5 mV to deliver 10 mA cm−2 for OER and an onset potential of 0.92 V to drive ORR. Its bifunctional catalytic activities outperform those of the composite catalyst Pt/C + RuO2 and most bifunctional catalysts reported. The experimental results and density functional theory calculations have demonstrated that the interplay between FeCo NPs and NCNT and the presence of N,P‐codoped carbon structure play important roles in increasing the catalytic activities of the NPC/FeCo@NCNT. More impressively, the NPC/FeCo@NCNT can be used as the air‐electrode catalyst, improving the performance of rechargeable liquid and flexible all‐solid‐state zinc–air batteries. [ABSTRACT FROM AUTHOR]

• P-doped aminated CNTs supported CoP/NiCoP hetero-nanoparticles (CoP/NiCoP@P-ACNTs) is prepared. • The in-situ phosphorization from the single phase material enables the formation of the CoP/NiCoP heterostructure. • It is demonstrated to be an efficient and stable catalyst for HER over the universal pH range. • The high catalytic activities arise from the strong electronic couplings between CoP, NiCoP, and P-ACNTs. • It can make the ΔGH* value of the CoP/NiCoP@P-ACNTs close to zero and lower the energy barrier for water dissociation. Developing an efficient catalyst for pH-Universal hydrogen evolution is of great interest. This work reports the synthesis of P-doped aminated CNTs supported CoP/NiCoP hetero-nanoparticles (CoP/NiCoP@P-ACNTs) through the in-situ phosphorization of the single phase NiCo 2 O 4 grown on the ACNTs. The in-situ phosphorization from the single phase material enables the formation of the CoP/NiCoP heterostructure, facilitating an electronic coupling between CoP and NiCoP. The CoP/NiCoP@P-ACNTs is demonstrated to be an efficient and stable catalyst for the hydrogen evolution reaction (HER) over the universal pH range. Specifically, it only needs overpotentials of 26.0, 94.0, and 76.8 mV to drive the current density of 10 mA cm−2 in the acidic, neutral, and alkaline solutions, respectively. All of these values are close to those of Pt/C and lower than those of many other catalysts reported recently. The DFT calculations indicate that the high catalytic activities of the CoP/NiCoP@P-ACNTs for the HER arise from the electronic couplings between CoP, NiCoP, and P-ACNTs. They can make the ΔG H* value of the CoP/NiCoP@P-ACNTs close to zero and lower the energy barrier for water dissociation. The CoP/NiCoP@P-ACNTs derived from the in-situ phosphorization of the single phase NiCo 2 O 4 is demonstrated to be an efficient pH-universal catalyst for the HER, which arises from the strong electronic couplings between CoP, NiCoP, and P-ACNTs. [Display omitted] [ABSTRACT FROM AUTHOR]

The development of highly-efficient and noble-metal-free catalysts with low cost and high durability for hydrogen evolution reaction (HER) is of great importance to many energy-related technologies. This work reports that nitrogen-doped carbon coated Co nanoparticles encapsulated in bamboo-like nitrogen-doped carbon nanotubes (Co@NC/B-NCNTs), synthesized by a simple calcination of Co(NO 3) 2 , melamine and P123, is a promising catalyst for HER in both acidic and alkaline solutions. In acidic solution, the Co@NC/B-NCNTs has the HER onset potential of ∼0 V and only needs an overpotential of 7 mV to drive the current density of 10 mA cm−2. Its HER catalytic activity is very close to that of Pt/C. In alkaline solution, its onset potential and overpotential to drive 10 mA cm−2 are 100 and 182 mV, respectively. Both the values are lower than those of many other catalysts reported. The DFT calculations show electronic coupling between Co nanoparticles and NC layer plays an important role in high catalytic activity of Co@NC/B-NCNTs. The Co nanoparticles can change the charge density distribution of the outer NC layer, affecting its properties for hydrogen adsorption and desorption. Additionally, the pyridinic N in the outer NC layer is calculated to be a promising active site for HER. The Co@NC/B-NCNTs has demonstrated to be an active catalyst for the HER in both the acidic and alkaline solutions, with the activity comparable to that of the Pt/C in the acidic solution. Image 1 • Nitrogen doped carbon coated Co nanoparticles encapsulated in bamboo-like nitrogen doped carbon nanotubes is synthesized. • Co@NC/B-NCNTs) is highly active for the HER in both the acidic and alkaline solutions. • Its HER catalytic activity is very close to that of the Pt/C, a benchmark catalyst for the HER. • The Co nanoparticles can change the charge density distribution of the outer NC layer, reducing the.|ΔG H∗ | value for hydrogen adsorption and desorption. • The calculation shows that the pyridinic N in the outer NC layer can be a promising active site for the HER. [ABSTRACT FROM AUTHOR]

Here, a simple, economical one-step doping strategy is adopted to prepare N, S co-doped graphene hollow spheres (NSGHS). The NSGHS exhibits remarkable oxygen-reduction-reaction (ORR) activity with a high half-wave potential (E 1/2) of 0.847 V vs. RHE and considerable long-term stability. When applied as anode materials for sodium-ion batteries (SIBs), it could deliver a high reversible capacity of 385 mAh g−1 at 500 mA g−1, excellent rate performance of 308 mAh g−1 at even 20 A g−1 and superior cycling performance at 10 A g−1 during 5000 cycles with negligible capacity fade. DFT calculation reveals that the doping of N and S endows the surrounding carbon with high positive charge and spin density, respectively, making them be highly active ORR catalytic sites except for S itself. Despite the possible oxidization of C–S–C active sites, the rest C atoms of NSGHS will still hold a considerably high catalytic activity superior to those of mono-doped or undoped cases. In addition, S doping will improve the binding between Na and graphene substrate to get a high capacity and N doping effectively curbs the rising of oxygen levels and oxidization of S in C–S–C active sites, thus the excellent stability for ORR and SIBs. [Display omitted] • A simple, economical one-step doping strategy is adopted to prepare NSGHS. • The NSGHS exhibits excellent ORR activity and Na storage performance. • The doping of N and S endows the surrounding carbon with high positive charge and spin density. • S doping will improve the binding between Na and graphene substrate to get a high capacity. • N doping effectively curbs the rising of oxygen levels and oxidization of S in C–S–C active sites. [ABSTRACT FROM AUTHOR]

The Co 2 P-Ni 2 P/NF is demonstrated to be an efficient catalyst for HER and OER. Post-analysis shows the structure changes of the Co 2 P-Ni 2 P/NF during the initial periods of both HER and OER. • The Co 2 P-Ni 2 P/NF is synthesized by in situ growth of Co 2 P-Ni 2 P on the nickel foam. • It shows superhigh and stable catalytic activities for both the HER and the OER. • The structural evolutions of the Co 2 P-Ni 2 P/NF are systematically investigated. • It shows excellent performance for overall water splitting. Understanding of the structure changes of the catalysts during hydrogen (HER) and oxygen (OER) evolution reactions is of paramount importance for design of catalysts with enhanced performance. This work reports the structure change investigations of phosphide-based catalysts in both HER and OER. Specifically, nickel foam supported Co 2 P-Ni 2 P (Co 2 P-Ni 2 P/NF) is synthesized by in-situ growth of Co 2 P-Ni 2 P on the current collector, i.e. nickel foam, and then used for the investigation of the structure changes during HER and OER. This method avoids the use of polymer binders, allowing for the systematic analysis of the structure changes of the catalysts after HER and OER. The obtained Co 2 P-Ni 2 P/NF shows an excellent catalytic bifunctionality for HER and OER in alkaline solutions. It only needs an overpotential of 90 mV vs RHE to offer a current density of 10 mA cm−2 for HER and needs an overpotential of 230 mV vs RHE to offer a current density of 50 mA cm−2 for OER. Both HER and OER activities of Co 2 P-Ni 2 P/NF are higher than those of most bifunctional catalysts reported. Post-analysis shows the occurrence of the surface roughening and the formation of M P O (M Co and Ni) at the surface in its initial period of the HER, and the surface roughening and the formation of a thin layer of amorphous MOOH (M Co and Ni) at the surface in its initial period of OER. The surface roughening and formation of M P O and amorphous hydroxide layer can be attributed to the main reason responsible for its high performance for HER and OER. Additionally, the Co 2 P-Ni 2 P/NF is also usable as both the cathode and anode for an electrolyzer for overall water splitting and shows high performance. [ABSTRACT FROM AUTHOR]

• Plasma-assisted phosphorization could construct Ni 12 P 5 /ZnP 2 heterojunction. • The P-Ni/MoS 2 @Ni 12 P 5 /ZnP 2 is an excellent bifunctional catalyst. • It needs an overpotential of 82 mV vs. RHE to offer 10 mA cm−2 for HER. • It needs an overpotential of 360 mV vs. RHE to offer 100 mA cm−2 for OER. • The P-Ni/MoS 2 @Ni 12 P 5 /ZnP 2 (+, −) alkaline elctrolyzer showed superior performance. Plasma assisted phosphorization is employed to obtain homogeneous nickel phosphide and zinc phosphide nanoparticles (NPs) distributed over the surface of MoS 2 nanosheets. It exhibits admirable bifunctional catalysis activity towards water electrolysis. [Display omitted] Herein, Zn single atom supported MoS 2 nanosheets growing on nickel foam (NF) is formed by in-situ growth of MoS 2 nanosheets and ZIF-8 and high temperature carbonization. And then plasma-assisted-phosphorization is employed to obtain homogeneous nickel phosphide (Ni 12 P 5) and zinc phosphide (ZnP 2) heterojunction nanoparticles (NPs) distributed over the surface of MoS 2 nanosheets (P-Ni/MoS 2 @Ni 12 P 5 /ZnP 2). The MoS 2 nanosheets growing on 3D NF framework benefits the increase of the electrochemically active specific surface, and the uniform distribution of heterojunction Ni 12 P 5 /ZnP 2 NPs exposes more catalytic active sites. Moreover, the heterojunction Ni 12 P 5 /ZnP 2 NPs obtained by plasma-assisted-phosphorization has smaller size and stronger electronic coupling than that synthesized by the conventional thermal phosphorization (C-Ni/MoS 2 @Ni 12 P 5 /ZnP 2). Therefore, the as-synthesized P-Ni/MoS 2 @Ni 12 P 5 /ZnP 2 shows an excellent bifunctionality catalytic activity for both HER and OER in alkaline solutions, which is highlighted by the overpotential at 82 mV for delivering current density of 10 mA cm−2 for HER and 360 mV for delivering 100 mA cm−2 for OER. P-Ni/MoS 2 @Ni 12 P 5 /ZnP 2 exhibits higher electrocatalytic performance and better stability than most previously reported bifunctional catalysts. Furthermore, the catalytic current density of P-Ni/MoS 2 @Ni 12 P 5 /ZnP 2 as a bifunctional catalyst assembled single two-electrode-electrolyzer rapidly exceeded 50 mA cm−2 at a low cell voltage of 1.62 V, surpassing the commercial RuO 2 -Pt/C coupled electrolyzer. [ABSTRACT FROM AUTHOR]