Electrochemical water splitting is considered as the most promising technology for hydrogen production. Considering overall water splitting for practical applications, catalysis of the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) should be performed in the same electrolyte, especially in alkaline solutions. However, designing and searching for highly active and inexpensive electrocatalysts for both OER and HER in basic media remain significant challenges. Herein, we report a facile and universal strategy for synthesizing nonprecious transition metals, binary alloys, and ternary alloys encapsulated in graphene layers by direct annealing of metal–organic frameworks. Density functional theory calculations prove that with an increase in the degree of freedom of alloys or a change in the metal proportions in FeCoNi ternary alloys, the electronic structures of materials can also be tuned intentionally by changing the number of transferred electrons between alloys and graphene. The optimal material alloys FeCo and FeCoNi exhibited remarkable catalytic performance for HER and OER in 1.0 M KOH, reaching a current density of 10 mA cm–2 at low overpotentials of 149 mV for HER and 288 mV for OER. In addition, as an overall alkaline water electrolysis, they were comparable to that of the Pt/RuO2 couple, along with long cycling stability.

Manganese (Mn) is generally regarded as not being sufficiently active for the oxygen reduction reaction (ORR) compared to other transition metals such as Fe and Co. However, in biology, manganese-containing enzymes can catalyze oxygen-evolving reactions efficiently with a relative low onset potential. Here, atomically dispersed O and N atoms coordinated Mn active sites are incorporated within graphene frameworks to emulate both the structure and function of Mn cofactors in heme-copper oxidases superfamily. Unlike previous single-metal catalysts with general M-N-C structures, here, it is proved that a coordinated O atom can also play a significant role in tuning the intrinsic catalytic activities of transition metals. The biomimetic electrocatalyst exhibits superior performance for the ORR and zinc-air batteries under alkaline conditions, which is even better than that of commercial Pt/C. The excellent performance can be ascribed to the abundant atomically dispersed Mn cofactors in the graphene frameworks, confirmed by various characterization methods. Theoretical calculations reveal that the intrinsic catalytic activity of metal Mn can be significantly improved via changing local geometry of nearest coordinated O and N atoms. Especially, graphene frameworks containing the Mn-N O cofactor demonstrate the fastest ORR kinetics due to the tuning of the d electronic states to a reasonable state.

Graphene, a 2D material consisting of a single layer of sp -hybridized carbon, exhibits inert activity as an electrocatalyst, while the incorporation of heteroatoms (such as N) into the framework can tune its electronic properties. Because of the different electronegativity between N and C atoms, electrons will transfer from C to N in N-doped graphene nanosheets, changing inert C atoms adjacent to the N-dopants into active sites. Notwithstanding the achieved progress, its intrinsic activity in acidic media is still far from Pt/C. Here, a facile annealing strategy is adopted for Ir-doped metal-organic frameworks to synthesize IrCo nanoalloys encapsulated in N-doped graphene layers. The highly active electrocatalyst, with remarkably reduced Ir loading (1.56 wt%), achieves an ultralow Tafel slope of 23 mV dec and an overpotential of only 24 mV at a current density of 10 mA cm in 0.5 m sulfuric acid solution. Such superior performance is even superior to the noble-metal catalyst Pt. Surface structural and computational studies reveal that the superior behavior originates from the decreased ΔG for HER induced by the electrons transferred from the alloy core to the graphene layers, which is beneficial for enhancing CH binding.

Developing highly active electrocatalysts with superior durability for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in the same electrolyte is a grand challenge to realize the practical application of electrolysis water for producing hydrogen. In this work, an ultrasmall Ru/Cu‐doped RuO2 complex embedded in an amorphous carbon skeleton is synthesized, through thermolysis of Ru‐modified Cu‐1,3,5‐benzenetricarboxylic acid (BTC), as a highly efficient bifunctional catalyst for overall water splitting electrocatalysis. The ultrasmall Ru nanoparticles in the complex expose more activity sites for hydrogen evolution and outperform the commercial Pt/C. Meanwhile, the ultrasmall RuO2 nanoparticles exhibit superior oxygen evolution performance over commercial RuO2, and the doping of Cu into the ultrasmall RuO2 nanoparticles further enhances the oxygen evolution performance of the catalyst. The outstanding OER and decent HER catalytic activity endow the complex with impressive overall water splitting performance superior to that of the state‐of‐the‐art electrocatalysts, which just require 1.47 and 1.67 V to achieve a current density of 10 mA cm−2 and 100 mA cm−2. The density functional theory calculations reveal that a Cu dopant could effectively tailor the d‐band center, thereby tuning electronic structure of Ru activity sites on the RuO2 (110) plane and ultimately improving the OER performance of RuO2.