Improving the utilization of Ir electrocatalysts for the oxygen evolution reaction (OER) to significantly reduce their loading is essential for low-cost hydrogen production in proton exchange membrane water electrolysis. Herein, IrCo hollow nanospheres featuring a novel structure with ultrathin continuous shells which have only eleven atomic layers (2.26 nm) were synthesized by a facile sequential reduction route using NaBH₄ as a reducing agent at room temperature. It is revealed that the key intermediate in the formation of hollow nanospheres is amorphous cobalt boride formed between Co²⁺ and NaHB₄ in the first reducing step. The average diameter of the IrCo nanospheres was found to be 73.71 nm with the atomic ratio of 47.1% and 52.9% for Co and Ir, respectively. The IrCo hollow nanospheres exhibit highly efficient OER activity and long-term durability with a low overpotential of 284 mV at 10 mA cm⁻² (32.5 μg_Ir cm⁻²) and a high mass activity of 8.49 A mg⁻¹ (5.7 times higher than that of commercial IrO₂ (1.49 A mg⁻¹) at 1.7 V. The performance is also proved using an overall water splitting device with the overpotential of 318 mV to achieve 10 mA cm⁻² as well as a 17 mV shift at 5 mA cm⁻² after 14 h. This improvement is critically attributed to the advantages of the hollow structure, ultrathin continuous shells which are oxidized into IrO_x in situ and strong lattice strain effects induced by the specific hollow structure and alloying Co into Ir crystal lattices (1.6% against metallic iridium). These characteristics endow the hollow nanospheres with great potential to minimize the Ir loading dramatically for practical applications, compared to other previously reported structures like nanoparticles, nanoneedles and nanowires.

中文翻译：

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超薄壳IrCo空心纳米球作为在酸性介质中进行氧气释放反应的高效电催化剂

对于质子交换膜水电解中低成本制氢而言，提高Ir催化剂在氧释放反应（OER）中的利用率以显着降低其负载量至关重要。在此，在室温下使用NaBH ₄作为还原剂，通过简便的连续还原路线，合成了具有仅具有十一个原子层（2.26nm）的超薄连续壳的新颖结构的IrCo中空纳米球。结果表明，形成空心纳米球的关键中间体是Co ²⁺与NaHB ₄之间形成的非晶硼化钴。在第一步还原中。发现IrCo纳米球的平均直径为73.71 nm，Co和Ir的原子比分别为47.1％和52.9％。所述IRCO中空纳米球在10mA厘米表现出高效率的OER活性和长期耐久性具有低超电势284毫伏^-2（32.5微克_的Ir厘米^-2）和8.49毫克阿高质量活性^-1（高5.7倍比商用IrO ₂（1.49 A mg ^-1）在1.7 V时的性能好。还使用整体分水装置证明了性能，该分水器的过电势为318 mV，可实现10 mA cm ^-2，在5时的位移为17 mV mA cm ^-214小时后。这种改进主要归因于以下优势：空心结构，原位被氧化成IrO _x的 超薄连续壳以及特殊的空心结构以及将Co合金化为Ir晶格（相对于金属铱为1.6％）引起的强晶格应变效应。与其他先前报道的结构（如纳米粒子，纳米针和纳米线）相比，这些特性赋予空心纳米球很大的潜力，可将实际应用中的Ir负载显着降至最低。