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Electrochemical water splitting is considered a green and sustainable method of producing hydrogen energy. Herein, to pursue a highly efficient hydrogen evolution reaction, we fabricated high-performance electrocatalysts, by utilizing a bimetallic (Cu and Co) metal–organic framework to modify rGO through a one-step in situ approach. The synthesized CuCoOC@rGO presents a highly ordered structure with a defect-rich porous surface for the hydrogen evolution reaction (HER). Specifically, the appropriate adjustment of metal (Cu and Co), 1,3,5-benzenetricarboxylic acid (H3BTC), and rGO ratios leads to a well-defined morphology, which creates a defect-rich porous surface. Characterized by XRD, SEM, EDS, FT-IR spectroscopy, Raman spectroscopy, XPS, and BET, the morphology exposes more active sites, strong evidence for the promotion of electrocatalytic efficiency. Upon the analysis of the experimental data, the obtained CuCoOC@rGO catalyst exhibits excellent activity in alkaline media with a low overpotential of 120 mV at a current density of 10 mA cm−2, and a Tafel slope of 124 mV dec−1 for the hydrogen evolution reaction (HER). Guided by the structure–activity relationship, the superior HER activity of CuCoOC@rGO in alkaline electrolyte could originate from many sources, including: (1) as a self-supported substrate, CuCoOC@rGO not only leads to profitable electrical contact and mechanical stability but also firmly roots into the rGO without extra binders. (2) The highly ordered structure provides smooth ion and electron transport channels, which are conducive to electrolyte infiltration and gas release. (3) The abundance of defective pores on the surface of the nanoarrays, which offers more active sites for the catalytic process. This study provides new prospects for the rational design and fabrication of advanced hierarchical functional electrocatalysts for application in electrochemical energy devices. [ABSTRACT FROM AUTHOR]

The development of high activity, low-cost and stability hydrogen evolution reaction (HER) catalysts is a core issue in the field of water splitting. Herein, the bimetallic CoMo MOFs-derived N-doped carbon nanospheres with Co/Mo–N bonds is proposed to effectively improve the electrocatalytic HER performance. Meanwhile, the combination of the porous and spherical structure further promotes the effective contact on the electrode/electrolyte interface while enhancing the electrolyte into the inner structure of the material for a fast HER process. In addition, the N-doped and bimetallic Co/Mo oxides on the rough surface of nanospheres have the capability to furnish more electrocatalytic active sites. The obtained electrocatalyst owns the small overpotential of 112 mV at 10 mA cm−2 and Tafel slope of 106.8 mV dec−1 in 1.0 M KOH solution. This work provides a new prospect for the rational design and fabrication of bimetallic active sites in carbon nanomaterials electrocatalysts in the relevant energy applications. [Display omitted] • Bimetallic CoMo MOFs-derived N-doped carbon nanospheres is proposed to effectively improve the electrocatalytic HER performance. • The formation of Co–N and Mo–N, which would provide a fast electron transfer path in electrocatalytic process. • The formation of CoO and CoMoO 3 species could synergistic promote the adsorption and reaction of the H ads intermediates. [ABSTRACT FROM AUTHOR]

Fabrication of highly efficient and earth-abundant bifunctional electrocatalyst to accelerate the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are critical for overall water splitting. In this work, bimetallic Co/Mo oxides modified reduced graphene oxide (rGO) was synthesized using a simple one-pot hydrothermal method, which significantly improved the electrocatalytic activity in both HER and OER. Under the optimal conditions, the double layer capacitance of rGO modified by Co/Mo bimetal is 78.08 mF cm−2. The overpotential required for HER to reach -10 mA cm−2 current density is 488 mV, the dynamic Tafel slope is 126 mV dec−1. The overpotential required for OER to reach 10 mA cm−2 current density is 420 mV, the slope of kinetic Tafel is 169 mV dec−1. This work provides a new prospect for the rational design and fabrication of efficient HER/OER bifunctional electrocatalysts in electrochemical energy device application.Graphical Abstract: Fabrication of highly efficient and earth-abundant bifunctional electrocatalyst to accelerate the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are critical for overall water splitting. In this work, bimetallic Co/Mo oxides modified reduced graphene oxide (rGO) was synthesized using a simple one-pot hydrothermal method, which significantly improved the electrocatalytic activity in both HER and OER. Under the optimal conditions, the double layer capacitance of rGO modified by Co/Mo bimetal is 78.08 mF cm−2. The overpotential required for HER to reach -10 mA cm−2 current density is 488 mV, the dynamic Tafel slope is 126 mV dec−1. The overpotential required for OER to reach 10 mA cm−2 current density is 420 mV, the slope of kinetic Tafel is 169 mV dec−1. This work provides a new prospect for the rational design and fabrication of efficient HER/OER bifunctional electrocatalysts in electrochemical energy device application. [ABSTRACT FROM AUTHOR]