The rational design of an efficient and inexpensive electrocatalyst based on earth-abundant 3d transition metals (TMs) for the hydrogen evolution reaction still remains a significant challenge in the renewable energy area. Herein, a novel and effective approach is developed for synthesizing ultrafine Co nanoparticles encapsulated in nitrogen-doped carbon nanotubes (N-CNTs) grafted onto both sides of reduced graphene oxide (rGO) (Co@N-CNTs@rGO) by direct annealing of GO-wrapped core-shell bimetallic zeolite imidazolate frameworks. Benefiting from the uniform distribution of Co nanoparticles, the in-situ-formed highly graphitic N-CNTs@rGO, the large surface area, and the abundant porosity, the as-fabricated Co@N-CNTs@rGO composites exhibit excellent electrocatalytic hydrogen evolution reaction (HER) activity. As demonstrated in electrochemical measurements, the composites can achieve 10 mA cm at low overpotential with only 108 and 87 mV in 1 m KOH and 0.5 m H SO , respectively, much better than most of the reported Co-based electrocatalysts over a wide pH range. More importantly, the synthetic strategy is versatile and can be extended to prepare other binary or even ternary TMs@N-CNTs@rGO (e.g., Co-Fe@N-CNTs@rGO and Co-Ni-Cu@N-CNTs@rGO). The strategy developed here may open a new avenue toward the development of nonprecious high-performance HER catalysts.

2D nanofilms assembled by pure protein with a macroscopic area and multiple functions can be directly formed at the air/water interface or at the solid surface at a timescale of several minutes. The multifunctionality of the nanofilm coating is demonstrated by both top-down and bottom-up micro-/nanoscale interfacial engineering, including surface modification, all-water-based photo/electron-beam lithography, and electroless deposition.

from electric energy into chemical energy, but also offers a promising platform for utilizing intermittently renewable energy sources (e.g., wind and solar). [1][2][3] To improve the splitting efficiency, precious Pt-based and Ir/Ru-based electrocatalysts are usually employed in the practical electro lysis to reduce the activation energy barriers of two core half-reactions involved in water splitting, i.e., hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. [4,5] Unfortunately, the large-scale utilization of these noble metals has been severely blocked by their limited abundance and high cost. As such, numerous endeavors have been undertaken to exploit for an alternative to noble catalysts during the past decades. [6][7][8][9][10] Emerging as a new class of crystalline materials, metal-organic frameworks (MOFs) constructed by bridging metal ions with organic linkers have drawn considerable attention to themselves owing to their porous, high specific surface, and tailorable features. [11][12][13][14] In recent years, MOFs have also been demonstrated as an ideal precursor to fabricate functional transition metal (TM)-carbon-based nanohybrids, which hold great promise as low-cost and efficient electrocatalysts for water splitting. [15][16][17][18][19][20] Since the chemical and the physical properties of the MOFsderived TM-carbon-based nanohybrids are highly dependent on the MOF precursors, it has been widely acknowledged that building MOF precursors with favorable composition, morphology, and surface structure is a prerequisite to enable these nanohybrids with satisfactory electrocatalytic activity. [21] To this end, there has been much attention surrounding the dedicate design of MOF precursors. [22][23][24][25][26][27][28][29][30][31][32] Currently, most work basically focus on the 3D MOF precursors owing to their high structural stability, large specific surface areas, and abundant pores. [24,25] After a refined post-treatment, their derived TM-carbon-based nanohybrids can inherit well original 3D nanostructure. Furthermore, the solid feature of MOF precursor is turned to the hollow counterpart sometimes. [26,27] These merits ensure the rapid mass transfer ability and rich potential active sites, thus improving the electrocatalytic activity. For instance, Pan et al. synthesized well-inherited hollow CoP@NC nanohybrids by direct calcination of well-performed core-shell CoZn-ZIF dodecahedra under Ar at 900 °C followed by an oxidationphosphorization process, which showed remarkable OER catalytic activity with an overpotential of 310 mV to drive a current Construction of well-defined metal-organic framework precursor is vital to derive highly efficient transition metal-carbon-based electrocatalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in water splitting. Herein, a novel strategy involving an in situ transformation of ultrathin cobalt layered double hydroxide into 2D cobalt zeolitic imidazolate framework (ZIF-67) nanosheets grafted with 3D ZIF-67 p...

The conversion of crystalline metal–organic frameworks (MOFs) into metal compounds/carbon hybrid nanocomposites via pyrolysis provides a promising solution to design electrocatalysts for electrochemical water splitting. However, pyrolyzing MOFs generally involves a complex high‐temperature treatment, which can destroy the coordinated surroundings within MOFs, and as a result not taking their full advantage of their electrolysis properties. Herein, a simple and room‐temperature boronization strategy is developed to convert nickel zeolite imidazolate framework (Ni‐ZIF) nanorods into ultrathin Ni‐ZIF/NiB nanosheets with abundant crystalline–amorphous phase boundaries. The combined experiment, and theoretical calculation results disclose that the ultrathin thickness allows fast electron transfer and ensures increased exposure of surface coordinatively unsaturated active sites while the crystalline–amorphous interface elaborately changes the potential‐determining step to energetically favorable intermediates. As a result, Ni‐ZIF/NiB nanosheets supported on nickel foam (NF) require overpotentials of 67 mV for the hydrogen evolution reaction and 234 mV for the oxygen evolution reaction to achieve a current density of 10 mA cm−2. Remarkably, Ni‐ZIF/NiB@NF as a bifunctional electrocatalyst for overall water splitting enables an alkaline electrolyzer with 10 mA cm−2 at an ultralow cell voltage of 1.54 V. The present work may open a new avenue to the design of MOF‐derived composites for electrocatalysis.

Developing cost-effective and highly efficient bifunctional electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of great interest for overall water splitting but still remains a challenging issue. Herein, a self-template route is employed to fabricate a unique hybrid composite constructed by encapsulating cobalt nitride (CoN) nanoparticles within three-dimensional (3D) N-doped porous carbon (CoN NP@N-PC) polyhedra, which can be served as a highly active bifunctional electrocatalyst. To afford a current density of 10 mA cm, the as-fabricated CoN NP@N-PC only requires overpotentials as low as 149 and 248 mV for HER and OER, respectively. Moreover, an electrolyzer with CoN NP@N-PC electrodes as both the cathode and anode catalyst in alkaline solutions can drive a current density of 10 mA cm at a cell voltage of only 1.62 V, superior to that of the Pt/IrO couple. The excellent electrocatalytic activity of CoN NP@N-PC can be mainly ascribed to the high inherent conductivity and rich nitrogen vacancies of the CoN lattice, the electronic modulation of the N-doped carbon toward CoN, and the hierarchically porous structure design.

A key factor for successful design of bioactive complex, organic-inorganic hybrid biomaterials is the facilitation and control of adhesion at interfaces, as many current synthetic biomaterials are inert, lacking interfacial bio activity. In this regard, the development of a simple, unified way to bio functionalize diverse organic and inorganic materials toward biomineralization remains a critical challenge. In this report, a universal biomimetic mineralization route that can be applied to virtually any type and morphology of scaffold materials is provided to induce nucleation and growth of hydroxyapatite (HAp) crystals based on phase-transited lysozyme (PTL) coating. Surface-anchored abundant functional groups in the PTL enrich the interface with strongly bonded calcium ions, facilitating the formation of HAp crystals in simulated body fluid with the morphology and alignment being similar to that observed in natural HAp in mineralized tissues. By the adhesion of amyloid contained in the PTL, such protein assembly could readily integrate HAp on ceramics, metals, semiconductors, and synthetic polymers irrespective of their size and morphology, with robust bonding stability and corresponding ultralow wear extent under normal bone pressure. This strategy successfully improves the in vivo osteoconductivity of Ti-based implant, underpinning the expectation for such biomaterial in future biointerface and tissue engineering.

increasing interest since it exhibits a suppressed Fenton reactivity in comparison to Fe-N-C while maintains a remarkable catalytic activity. [18-20] To rationally design CoN -C catalyst for ORR, downsizing active species to single-atom scale and intentionally incorporating specific N into carbon matrix have been proposed to facilitate the catalytic process. [21-27] The former strategy can achieve a maximum atom-utilization efficiency and full exposure of active sites while the latter strategy usually involves pyridinic-N construction to optimize the charge distribution and improve the density of states at the Fermi level of the adjacent C atoms, facilitating the oxygen adsorption and reduction reaction. [28,29] For example, Yin et al. synthesized singleatom CoN x-C electrocatalyst through the pyrolysis of cobalt-coordinated framework porphyrin with graphene and found that it exhibited a high half-wave potential of 0.83 V, much better than Co nanoparticles-N-C electrocatalyst (0.73 V). [30] Han et al. investigated the size effect on the electrocatalytic activity of Co catalysts from nanometer to singleatom scale, demonstrating that cobalt single atoms on N-doped carbon could achieve a higher half-wave potential (0.82 V) and a larger limiting diffusion current density (4.96 mA cm −2) than atomic Co clusters (0.81 V, 4.44 mA cm −2) and Co nanoparticles counterpart (0.80 V, 3.86 mA cm −2). [31] Wang et al. developed a laser irradiation strategy to modulate the relative contents of pyridinic and pyrrolic nitrogen dopants in the electrocatalyst and reported that pyridinic-NCo bonding instead of pyrrolic-N bonding could optimize the adsorption energy of reaction intermediates in ORR process. [32] Despite prominent achievements that have been made recently, most studies on CoN -C catalysts focused on only one of the above-proposed strategies, and thus their catalytic performance is still unsatisfied to meet the practical application. Therefore, developing an effective synthetic strategy for the integration of generating atomically dispersed active sites and achieving pyridinic-N-optimized electronic structure to increase the catalytic activity of CoN -C catalyst is highly demanded but remains significant challenging. Herein, we have innovatively developed a highly effective lysozyme (Lys)-assisted metal-organic framework (MOF) approach to prepare single-atom Co implanted pyridinic-N doped porous carbon catalysts. During the pyrolysis process, the attached Lys on the surrounding of Co-ZIF-8 (zeolitic imidazolate frameworks) not only can effectively trap metal atoms Engineering transition metal-nitrogen-carbon (TM-N-C) catalysts with highdensity accessible active sites and optimized electronic structure holds great promise in the context of the electrochemical oxygen reduction reaction (ORR). Herein, a novel modification of a lysozyme-modified zeolitic imidazolate framework with isolated Co atoms anchored on dominated pyridinic-N doped carbon (Co-pyridinic N-C) is reported. The atomically dispersed Co allows the maximum ...

Exploring highly‐efficient and low‐cost electrodes for both hydrogen and oxygen evolution reaction (HER and OER) is of primary importance to economical water splitting. Herein, a series of novel and robust bifunctional boride‐based electrodes are successfully fabricated using a versatile Et2NHBH3‐involved electroless plating (EP) approach via deposition of nonprecious boride‐based catalysts on various substrates. Owing to the unique binder‐free porous nodule structure induced by the hydrogen release EP reaction, most of the nonprecious boride‐based electrodes are highly efficient for overall water splitting. As a distinctive example, the Co‐B/Ni electrode can afford 10 mA cm−2 at overpotentials of only 70 mV for HER and 140 mV for OER, and can also survive at large current density of 1000 mA cm−2 for over 20 h without performance degradation in 1.0 m KOH. Several boride‐based two‐electrode electrolyzers can achieve 10 mA cm−2 at low voltages of around 1.4 V. Moreover, the facile EP approach is economically viable for flexible and large size electrode production.