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• Co-doped Ni 3 S 2 nanosheets assembled flower-like structure is grown on NF. • Co doping brings more active sites and enhanced catalysis kinetics. • Ultrathin nanosheets benefit high surface area and fast charge transfer. • Improved OER performances in alkaline media are achieved. Oxygen evolution reaction (OER) sets the huge obstacle for water electrolysis application, and the low-cost catalysts with small overpotential and fast kinetics are highly needed. Herein, cobalt-doped Ni 3 S 2 nanosheets constructed flower-like architecture is grown on nickel foam (Co-Ni 3 S 2 /NF) toward OER application. It is found that, heteroatom doping induces positive effects for OER, including the modulated electronic structure, more active sites, and accelerated charge transfer. Nanosheets structure assures exposed active sites and shortened charge transfer path. Benefited from the aforementioned advantages, the as-prepared sample exhibits impressive catalysis performances, such as ultralow overpotential of 160 mV at current density of 10 mA cm−2, small Tafel slope of 49 mV dec−1, and high stability, which behaves as the promising catalyst for OER. [ABSTRACT FROM AUTHOR]

• Electrochemical activation induces surface reconstruction of CoMo-LDH nanosheets. • The optimized electronic structure and enhanced intrinsic activity are obtained. • The increased catalysis sites and promoted charge transfer are achieved. • Generating 100 mA cm−2 at low overpotentials of 202 mV for HER. Surface reconstruction emerging in the electrochemical oxygen evolution process is regarded to be significantly important for the activated catalysis efficiency, however, which is rarely recognized for hydrogen evolution reaction (HER). Here, the electrochemical activation of CoMo layered double hydroxide (CoMo-LDH) nanosheet arrays is demonstrated to significantly activate the electrochemical HER property. The catalysis performance improvement originates from the surface transformation of CoMo-LDH to Co(OH) 2 /CoOOH, as well as the dissolution of Mo and its adsorption on the catalyst surface in K 2 Mo 3 O 10 phase. Based on the combined benefits of optimized electronic structure, increased catalysis sites, and promoted charge transfer, the overpotentials at catalysis current densities of 10 and 100 mA cm−2 are as low as 113 and 202 mV. This study demonstrates the electrochemical activation strategy to drive the surface reconstruction of bimetal hydroxides for enhanced HER performance, inspiring the research interests on the reconstruction and activation enhancement behaviors of HER electrocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sulfur on CoFe alloys embedded in nitrogen-doped carbon nanosheets is designed. • M−S n 2- is the robust catalysis sites for HER. • The synergisms between sulfur and CoFe@NC are beneficial for HER. • 2D NC interacted 3D network supplies easily accessible active sites and rapid charge transfer. • The present S-CoFe@NC exhibits Pt-like HER performance in neutral media. Seeking novel low-cost non-noble metal based electrocatalysts with high efficiency is of great significance to promote industrial application of hydrogen evolution reaction (HER). Herein, we originally demonstrate sulfur on CoFe alloys embedded in nitrogen-doped carbon nanosheets (S-CoFe@NC) catalyst with extremely robust HER activity in neutral media. The present sample exhibits active HER performance with ultralow overpotential of 37 mV at current density of 10 mA cm−2 and Tafel slope of 34 mV dec-1, which is the same as commercial Pt/C. Systemic studies show that strong interaction between bridging S n 2- and CoFe@NC introduces M−S n 2- as the robust catalysis sites for HER, which is also beneficial for the charge exchange. The specific structure of NC nanosheet interconnected network provides structure advantages for easily accessible active sites and fast charge transfer for electrocatalysis. Thus, this work paves a way for the development of new class of sulfur based electrocatalyst with efficient HER performance for neutral water splitting. [ABSTRACT FROM AUTHOR]