Realizing effective alkaline water/seawater electrolysis through efficient hydrogen and oxygen evolution reaction (HER and OER) electrocatalysts is demanding but attracts significant task. Herein, a novel NNNF@Mo 2 N/FeO x N y electrocatalyst comprising of Mo 2 N/FeO x N y interfacial rod-shaped structure on nitrogen-doped nickel nanosheets modified nickel foam (NF) (denoted NNNF) with remarkable HER and OER catalytic performance is reported. The nanosheet-rod structure coupled with multidimensional interfacial boundaries enriches the optimized NNNF@Mo 2 N/FeO x N y catalyst with rich active sites. As a result, the as-prepared NNNF@Mo 2 N/FeO x N y catalyst demands low overpotentials of 22/130 mV and 28/142 mV to drive current densities of 10/100 mA cm −2 for the HER, 222/348 mV and 239/361 mV for the OER in 1 M alkaline freshwater/seawater electrolytes, respectively. The catalyst also reveals excellent HER and OER stability for 100 h at a constant high current density of 100 mA cm −2 in both electrolytes. The catalyst also acts as bifunctional catalyst in overall water electrolytic devices requiring low overall voltages of 1.42/1.47 V@20 mA cm −2 in alkaline freshwater/seawater electrolytes, as well as considerable voltages of 1.50/1.81 V@100/500 mA cm −2 in 6 M KOH seawater electrolyte at 60 °C for industrial conditions.
Graphical We find that the N-doped Ni particles can enhance the adsorption of CO 2 and modulate the configuration of adsorbed CO on Ni-N-C sites. As a result, the optimal catalyst can efficiently convert CO 2 into CO with a faradaic efficiency of 96.7 % and a current density of 500 mA cm −2 in a strongly acidic electrolyte. Electro-chemically reducing CO 2 in a highly acidic medium is promising for addressing the issue of carbonate accumulation. However, the hydrogen evolution reaction (HER) typically dominates the acidic CO 2 reduction. Herein, we construct an efficient electro-catalyst for CO formation based on a core-shell structure, where nitrogen-doped Ni nanoparticles coexist with nitrogen-coordinated Ni single atoms. The optimal catalyst demonstrates a significantly improved CO faradaic efficiency (FE) of 96.7 % in the acidic electrolyte (pH=1) at an industrial-scale current density of 500 mA cm −2 . Notably, the optimal catalyst maintains a high FE of CO exceeding 90 % (current density=500 mA cm −2 ) in the electrolyte with a wide pH range from 0.67 to 14. In-situ spectroscopic characterization and density functional theory calculations show that the local electron density of Ni-N-C sites is enhanced by N-doped Ni particles, which facilitates the formation of *COOH intermediate and the adsorption of *CO. This study demonstrates the potential of a hybrid metal/Ni-N-C interface in boosting acidic CO 2 electro-reduction.
Electrolytic water splitting using renewable energy sources, such as solar power, provides a green and sustainable approach for hydrogen production. Anion exchange membrane (AEM) electrolyzers present substantial commercial prospects; however, the rate of hydrogen evolution reaction (HER) in alkaline electrolytes is limited by the water dissociation step. In this work, we fabricated an N-doped Ni substrate for loading ultrafine Pt nanoparticles, realizing spatial decoupling of the reaction process to break the limitation of water dissociation, where the N-doped Ni substrate and Pt nanoparticles facilitate the supply of ample H* and H2 release, respectively. The prepared Pt–N–Ni/NC with extremely low Pt loading (1.0 wt%) requires only 15 and 149 mV overpotentials to reach current densities of 10 and 1000 mA cm−2, respectively. When assembled into an AEM electrolyzer, the system requires a cell voltage of only 1.75 V to achieve a current density of 1000 mA cm−2. Notably, the solar-driven AEM electrolyzer demonstrates a current density of 1390 mA cm−2 with a solar-to-hydrogen efficiency (STH) of 8.27%. This study proposes a strategy to achieve efficient utilization and performance improvement of precious metals, promoting the development of efficient green hydrogen production.
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