Wu Ziyang, Liao Ting, Wang Sen, Mudiyanselage Janith Adikaram, Micallef Aaron S, Li Wei, O'Mullane Anthony P, Yang Jianping, Luo Wei, Ostrikov Kostya, Gu Yuantong, Sun Ziqi
School of Mechanical, Medical and Process Engineering, Queensland University of Technology, 2 George Street, Brisbane, QLD, 4000, Australia.
Centre for Materials Science, Queensland University of Technology, 2 George Street, Brisbane, QLD, 4000, Australia.
Nanomicro Lett. 2022 Apr 1;14(1):90. doi: 10.1007/s40820-022-00832-6.
Oxygen vacancies (V) in electrocatalysts are closely correlated with the hydrogen evolution reaction (HER) activity. The role of vacancy defects and the effect of their concentration, however, yet remains unclear. Herein, BiO, an unfavorable electrocatalyst for the HER due to a less than ideal hydrogen adsorption Gibbs free energy (ΔG), is utilized as a perfect model to explore the function of V on HER performance. Through a facile plasma irradiation strategy, BiO nanosheets with different V concentrations are fabricated to evaluate the influence of defects on the HER process. Unexpectedly, while the generated oxygen vacancies contribute to the enhanced HER performance, higher V concentrations beyond a saturation value result in a significant drop in HER activity. By tunning the V concentration in the BiO nanosheets via adjusting the treatment time, the BiO catalyst with an optimized oxygen vacancy concentration and detectable charge carrier concentration of 1.52 × 10 cm demonstrates enhanced HER performance with an overpotential of 174.2 mV to reach 10 mA cm, a Tafel slope of 80 mV dec, and an exchange current density of 316 mA cm in an alkaline solution, which approaches the top-tier activity among Bi-based HER electrocatalysts. Density-functional theory calculations confirm the preferred adsorption of H* onto BiO as a function of oxygen chemical potential (∆μ) and oxygen partial potential (P) and reveal that high V concentrations result in excessive stability of adsorbed hydrogen and hence the inferior HER activity. This study reveals the oxygen vacancy concentration-HER catalytic activity relationship and provides insights into activating catalytically inert materials into highly efficient electrocatalysts.
电催化剂中的氧空位（V）与析氢反应（HER）活性密切相关。然而，空位缺陷的作用及其浓度的影响仍不明确。在此，由于氢吸附吉布斯自由能（ΔG）不理想而对HER不利的电催化剂BiO被用作探索V对HER性能作用的理想模型。通过简便的等离子体辐照策略，制备了具有不同V浓度的BiO纳米片，以评估缺陷对HER过程的影响。出乎意料的是，虽然产生的氧空位有助于提高HER性能，但超过饱和值的更高V浓度会导致HER活性显著下降。通过调整处理时间来调节BiO纳米片中的V浓度，具有优化氧空位浓度和可检测电荷载流子浓度为1.52×10¹⁹ cm⁻³的BiO催化剂在碱性溶液中表现出增强的HER性能，过电位为174.2 mV时达到10 mA cm⁻²，塔菲尔斜率为80 mV dec⁻¹，交换电流密度为316 μA cm⁻²，这接近Bi基HER电催化剂中的顶级活性。密度泛函理论计算证实了H*在BiO上的优先吸附是氧化学势（∆μ）和氧分压（P）的函数，并表明高V浓度导致吸附氢的过度稳定，从而导致HER活性较差。这项研究揭示了氧空位浓度与HER催化活性的关系，并为将催化惰性材料激活为高效电催化剂提供了见解。
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