Developing active and durable electrocatalysts for overall water splitting is desirable but challenging to realize sustainable hydrogen production. Here, we report a facile and general method to prepare ultrafine nickel (Ni)-iridium (Ir) alloy nanoparticles/graphene hybrids for overall water splitting. The optimized hybrid with 4.9 wt% Ir exhibits much higher catalytic activity and durability than commercial 20 wt% Ir/C for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Theoretical simulations reveal that the incorporation of Ir in metallic Ni lattice regulates hydrogen adsorption free energy to the optimum level, thus improving HER activity, while in situ generated amorphous Ir-Ni hydr(oxy)oxides around metallic Ni-Ir core have been demonstrated to be the active species under OER conditions, which switches OER rate-determining step to energy-favorable pathway. The overall water splitting electrolyzer assembled by the optimized electrocatalyst shows a low cell voltage of only 1.52 V and excellent stability to deliver a current density of 10 mA cm⁻². This work provides a powerful strategy toward general synthesis of ultrafine alloy nanoparticles for high-performance overall water splitting.

开发用于整体水分解的活性和持久性电催化剂是理想的，但要实现可持续的氢气生产具有挑战性。在这里，我们报告了一种用于制备超细镍（Ni）-铱（Ir）合金纳米粒子/石墨烯杂化物以进行整体水分解的简便通用方法。具有优化的4.9 wt％Ir的杂化体对氧释放反应（OER）和氢释放反应（HER）的催化活性和耐久性均比市售20 wt％Ir / C高。理论模拟表明，在金属Ni晶格中掺入Ir可以将氢吸附自由能调节到最佳水平，从而在原位提高HER活性。已经证明，在金属ER-条件下，金属Ni-Ir核周围生成的无定形Ir-Ni氢氧化物是活性物种，这将OER速率确定步骤切换为能量有利的途径。由优化的电催化剂组装的整个水分解电解槽显示出仅1.52 V的低电池电压和出色的稳定性，可提供10 mA cm ^-2的电流密度。这项工作为全面合成超细合金纳米粒子提供了强有力的策略，以实现高性能的整体水分解。