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Scalable synthesis of highly efficient and nonprecious metal based catalysts for pH-universal hydrogen evolution reaction (HER) is a daunting challenge. In this work, we fabricated self-supported composites of (Ni,Co) 3 C mesoporous nanosheets/N-doped carbon with adjustable sizes from 1 cm × 1 cm to 25 cm × 25 cm using a facile and rapid electrodeposition, which was then followed by carbonization. The as-prepared catalyst shows small overpotentials of 58, 118, and 71 mV at 10 mA cm −2 in acid, neutral, and basic electrolytes, respectively with high exchange current densities. The above HER activities exceeded most non-noble metal caride-based catalysts in a pH-universal electrolyte. Theoretical calculations suggest that bimetallic carbide is favorable for HER because of its metallic conductivity, close-to-zero Gibbs free energy change (ΔG H* ), and downshifted dband center (ε d ) revealed by density of states (DOS). The outstanding performance can be attributed to the tunable ultrathin nanosheet-like structure, large specific surface area, and electronic structure modulations. Our work developed an efficient, controllable, and largescale synthesis of a cost-effective, highly efficient, high performance, and stable catalyst for hydrogen evolution reaction, which can operate in a wide pH range.

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The electrocatalysis conversion of N 2 to NH 3 at ambient conditions is promising for achieving clean and sustainable NH 3 production with low energy consumption. However, this process suffers from the low yield rate of NH 3 and low Faradaic efficiency (FE) by the previously reported electrocatalysts. In this work, a nanocomposite of nickel oxide coated with nitrogen-doped porous carbon distributed on graphite paper (N-C@NiO/GP) with remarkable electrocatalytic activity for nitrogen reduction reaction (NRR) is reported. N-C@NiO/GP attains an impressive Faradaic efficiency of 30.43% for NH 3 production, and the NH 3 yield rate reaches 14.022 μg h −1 mg cat.−1 (1.15 × 10 −10 mol s −1 cm −2 ) at −0.2 V vs the reversible hydrogen electrode. The composite also shows excellent electrocatalytic activity and structure stability with an electrocatalytic period of up to 20 h. When the 15 N 2 is used as the feeding gas, the produced species are 14 NH 4 + and 15 NH 4 + , which suggests that the reaction follows a Mars−van Krevelen mechanism. The synthesized NH 3 is determined from the introduced N 2 as indicated by no obvious change in N/Ni ratio. The microstructure before and after the durability test is similar and the catalytic performance during the 2 h NRR process, which is repeated six times, is stable. This work not only exploits an excellent electrocatalyst for N 2 fixation to NH 3 but also provides a direction for the inexpensive preparation of highly active and stable transition metal oxide catalysts.