Although electrocatalysts based on transition metal phosphides (TMPs) with cationic/anionic doping have been widely studied for hydrogen evolution reaction (HER), the origin of performance enhancement still remains elusive mainly due to the random dispersion of dopants. Herein, we report a controllable partial phosphorization strategy to generate CoP species within the Co‐based metal‐organic framework (Co‐MOF). Density functional theory calculations and experimental results reveal that the electron transfer from CoP to Co‐MOF through N‐P/N‐Co bonds could lead to the optimized adsorption energy of H2O (ΔGnormalH2normalO* ) and hydrogen (ΔGH*), which, together with the unique porous structure of Co‐MOF, contributes to the remarkable HER performance with an overpotential of 49 mV at a current density of 10 mA cm−2 in 1 m phosphate buffer solution (PBS, pH 7.0). The excellent catalytic performance exceeds almost all the documented TMP‐based and non‐noble‐metal‐based electrocatalysts. In addition, the CoP/Co‐MOF hybrid also displays Pt‐like performance in 0.5 m H2SO4 and 1 m KOH, with the overpotentials of 27 and 34 mV, respectively, at a current density of 10 mA cm−2.

Searching for non-noble metal based electrocatalysts with high efficiency and durability toward hydrogen evolution reaction (HER) is vitally necessary for the upcoming clean and renewable energy systems. Here we report the synthesis of CoP nanoparticles encapsulated in ultrathin nitrogen-doped porous carbon (CoP@NC) through a metal-organic framework (MOF) route. This hybrid exhibits remarkable electrocatalytic activity toward HER in both acidic and alkaline media, with good stability. The experiment and theoretical calculation reveal that the carbon atoms adjacent to N dopants on the shells of CoP@NC are active sites for hydrogen evolution, and CoP and N dopants synergistically optimize the binding free energy of H* on the active sites, which results in a higher electrocatalytic activity than its counterparts without nitrogen doping and/or CoP-encapsulation.

The search for highly efficient platinum group metal (PGM)‐free electrocatalysts for the hydrogen oxidation reaction (HOR) in alkaline electrolytes remains a great challenge in the development of alkaline exchange membrane fuel cells (AEMFCs). Here we report the synthesis of an oxygen‐vacancy‐rich CeO2/Ni heterostructure and its remarkable HOR performance in alkaline media. Experimental results and density functional theory (DFT) calculations indicate the electron transfer between CeO2 and Ni could lead to thermoneutral adsorption free energies of H* (ΔGH*). This, together with the promoted OH* adsorption strength derived from the abundance of oxygen vacancies in the CeO2 species, contributes to the excellent HOR performance with the exchange current density and mass activity of 0.038 mA cmNi−2 and 12.28 mA mgNi−1, respectively. This presents a new benchmark for PGM‐free alkaline HOR and opens a new avenue toward the rational design of high‐performance PGM‐free electrocatalysts for alkaline HOR.

The development of precious-metal-free electrocatalysts with high-efficiency for hydrogen evolution reaction (HER) at all pHs is of great interest for the development of electrochemical overall splitting technologies. Despite that intense efforts have been made to developing cost-effective electrocatalysts toward HER under both acidic and alkaline electrolytes with high efficiency, electrocatalysts with remarkable performance in neutral media are rare. Herein, N atoms doped Co2P nanorod arrays grown on carbon cloth (N–Co2P/CC) have been successfully synthesized and further used as efficient electrocatalysts for HER at all pH values. Specially, the N–Co2P/CC exhibits an overpotential of 42 mV at the current density of 10 mA cm –2 with long-term stability in 1.0 M PBS (phosphate-buffered solution), which is comparable to the benchmark Pt/CC. Density functional theory (DFT) calculations suggest nitrogen doping could tailor the electronic structure of Co2P, leading to optimized adsorption free energies of water (ΔG *H2O) and hydrogen (ΔG *H), facilitating hydrogen generation through the Volmer–Heyrovsky mechanism.

Searching for highly efficient and cost‐effective electrocatalysts toward the hydrogen evolution reaction (HER) in alkaline electrolyte is highly desirable for the development of alkaline water splitting, but still remains a significant challenge. Herein, the rational design of Cr‐doped Co4N nanorod arrays grown on carbon cloth (Cr–Co4N/CC) that can efficiently catalyze the HER in alkaline media is reported. It displays outstanding performance, with the exceptionally small overpotential of 21 mV to obtain the current density of 10 mA cm−2 and good stability in 1.0 m KOH, which is even better than the commercial Pt/C electrocatalyst, and much lower than most of the reported transition metal nitride‐based and other non‐noble metal‐based electrocatalysts toward the alkaline HER. Density functional theory (DFT) calculations and experimental results reveal that the Cr atoms not only act as oxophilic sites for boosting water adsorption and dissociation, but also modulate the electronic structure of Co4N to endow optimized hydrogen binding abilities on Co atoms, thereby leading to accelerating both the alkaline Volmer and Heyrovsky reaction kinetics. In addition, this strategy can be extended to other metals (such as Mo, Mn, and Fe) doped Co4N electrocatalysts, thus may open up a new avenue for the rational design of highly efficient transition metal nitride‐based HER catalysts and beyond.

Direct use of metal–organic frameworks (MOFs) with robust pore structures, large surface areas, and high density of coordinatively unsaturated metal sites as electrochemical active materials is highly desirable (rather than using as templates and/or precursors for high‐temperature calcination), but this is practically hindered by the poor conductivity and low accessibility of active sites in the bulk form. Herein, a universal vapor‐phase method is reported to grow well‐aligned MOFs on conductive carbon cloth (CC) by using metal hydroxyl fluorides with diverse morphologies as self‐sacrificial templates. Specifically, by further partially on‐site generating active Co3S4 species from Co ions in the echinops‐like Co‐based MOF (EC‐MOF) through a controlled vulcanization approach, the resulting Co3S4/EC‐MOF hybrid exhibits much enhanced electrocatalytic performance toward the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), with overpotentials of 84 and 226 mV required to reach a current density of 10 mA cm−2, respectively. Density functional theory (DFT) calculations and experimental results reveal that the electron transfer between Co3S4 species and EC‐MOF can decrease the electron density of the Co d‐orbital, resulting in more electrocatalytically optimized adsorption properties for Co. This study will open up a new avenue for designing highly ordered MOF‐based surface active materials for various electrochemical energy applications.

activities when compared to Pt/C is highly desirable, but still remains challenging.Transition metal phosphides (TMPs) have been investigated as a new class of effective HER catalysts due to their hydrogenase-like catalytic mechanism. [7] It has been reported that the introduction of phosphorus could modify the electronic structure of metal center, resulting in optimized reversible binding of hydrogen, which is considered as the key fact for boosting HER performance. [8] Despite intensive efforts have been made to develop pH-universal TMP-based electrocatalysts with both high-activity and long-term stability, only a few of them could exhibit comparable to, or even better activities than commercial Pt/C in acidic media. Adding insult to injury, Pt-free catalyst with superior catalytic performance to Pt/C under alkaline or/and neutral media has been rarely reported. Very recently, Li's group first reported the successful synthesis of Rh 2 P nanocubes with the average size of about 4.7 nm through a solvothermal method. [9] And the obtained Rh 2 P nanocubes exhibit good HER activities both in 0.5 m H 2 SO 4 and 0.1 m KOH. On the other hand, it is known that catalytic process occurs on the surface of catalysts, thus the size of catalysts is in connection with exposed active site numbers. [10] Experiment results show that nanocatalysts with decreased size often possess higher surface area and more active sites, resulting in enhanced catalytic activity. Consequently, developing ultrasmall TMPs with narrow size distribution may boost HER activity and even superior to the stateof-the-art Pt/C. Inspired by these ideas, in this work, we report the successful colloidal synthesis of monodisperse Rh 2 P nanoparticles (NPs) with an average size of 2.8 nm as well as their superior catalytic performances toward pH-universal HER. As expected, the monodisperse Rh 2 P NPs exhibit higher HER activities than Pt/C over a wide range of pH, with overpotentials of 14, 30, and 38 mV to achieve 10 mA cm −2 in 0.5 m H 2 SO 4 , 1.0 m KOH, and 1.0 m phosphate-buffered saline (PBS), respectively. As far as we know, this is the first example of Pt-free electrocatalyst possessing higher pH-universal HER performance than the state-of-the-art commercial Pt/C. Furthermore, density functional theory (DFT) calculations indicate that the H adsorption strength of Rh 2 P is weakened to nearly zero due to the introduction of P, thereby resulting in the outstanding HER performance.The search for Pt-free electrocatalysts exceeding pH-universal hydrogen evolution reaction (HER) activities when compared to the state-of-the-art commercial Pt/C is highly desirable for the development of renewable energy conversion systems but still remains a huge challenge. Here a colloidal synthesis of monodisperse Rh 2 P nanoparticles with an average size of 2.8 nm and their superior catalytic activities for pH-universal HER are reported. Significantly, the Rh 2 P catalyst displays remarkable HER performance with overpotentials of 14, 30, and 38 mV to achieve 10 mA cm −2 ...

3D ternary nickel iron sulfide microflowers with a hierarchically porous structure have been directly grown on Ni foam via a convenient two-step method for efficient bifunctional water splitting.