A highly active and stable oxygen evolution reaction (OER) electrocatalyst is critical for hydrogen production from water splitting. Herein, three-dimensional Ni₃S₂@graphene@Co₉₂S₈ (Ni₃S₂@G@Co₉S₈), a sandwich-structured OER electrocatalyst, was grown in situ on nickel foam; it afforded an enhanced catalytic performance when highly conductive graphene is introduced as an intermediary for enhancing the electron transfer rate and stability. Serving as a free-standing electrocatalytic electrode, Ni₃S₂@G@Co₉S₈ presents excellent electrocatalytic activities for OER: A low onset overpotential (2 mA·cm⁻² at 174 mV), large anode current density (10 mA·cm⁻² at an overpotential of 210 mV), low Tafel slope (66 mV·dec⁻¹), and predominant durability of over 96 h (releasing a current density of ∼14 mA·cm⁻² with a low and constant overpotential of 215 mV) in a 1 M KOH solution. This work provides a promising, cost-efficient electrocatalyst and sheds new light on improving the electrochemical performance of composites through enhancing the electron transfer rate and stability by introducing graphene as an intermediary.

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高活性和稳定的析氧反应（OER）电催化剂对于由水分解产生氢气至关重要。在此，在镍泡沫上原位生长了夹心结构的OER电催化剂三维Ni ₃ S ₂ @ graphene @ Co ₉₂ S ₈（Ni ₃ S ₂ @ G @ Co ₉ S ₈）。当引入高导电性石墨烯作为提高电子传输速率和稳定性的中间体时，它提供了增强的催化性能。作为独立的电催化电极，Ni ₃ S ₂ @ G @ Co ₉ S ₈对OER表现出优异的电催化活性：低的过电位（174 mV下为2 mA·cm ^-2），大的阳极电流密度（210 mV的下电位为10 mA·cm ^-2），低的Tafel斜率（66 mV·dec ^-1），在1 M KOH溶液中的主要耐久性超过96 h（电流密度约为-14 mA·cm ^-2，恒定且低电势为215 mV）。这项工作提供了一种有前途的，具有成本效益的电催化剂，并且通过引入石墨烯作为中介物，通过提高电子转移速率和稳定性，为改善复合材料的电化学性能提供了新的思路。

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