Baker Jordon, Wang Danyang, Alam Md Kawsar, Lao Ka Un, Arachchige Indika U
Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284-2006, United States.
Chem Mater. 2025 Apr 28;37(9):3260-3273. doi: 10.1021/acs.chemmater.4c03479. eCollection 2025 May 13.
Electrochemical water splitting represents a sustainable method for producing molecular hydrogen, a promising clean energy alternative to fossil fuels. Iron phosphides have emerged as earth-abundant catalysts for the hydrogen evolution reaction (HER), where performance can be enhanced by admixing synergetic metals to produce bimetallic catalysts. Herein, we report a theoretical and experimental study that reveals the influence of dopant-induced hexagonal to orthorhombic phase transition on the catalytic activity and stability of FeP nanorods (NRs) for HER. Among eight metal dopants computationally studied, Mo has been identified as the most promising dopant owing to its optimum hydrogen binding free energy (Δ ) on the FeP (210) surface. Accordingly, hexagonal and orthorhombic Fe Mo P NRs ( = 0-14%) with average lengths and widths ranging from 50.9 ± 22.1 to 92.4 ± 43.8 nm and 3.8 ± 1.0 to 6.3 ± 1.8 nm, respectively, were colloidally synthesized to investigate the structure- and composition-dependent HER activity. Upon incorporation of Mo, the underlying hexagonal FeP phase transformed into orthorhombic Fe Mo P when ≥ 0.11 (5.41%). The admixture of Mo caused variations in the surface chemistry, leading to a significant decrease in Fe and P charges. The HER performance was observed to be both phase- and composition-dependent with mixed-phase Fe Mo P NRs ( = 0.03, 0.06, and 0.09) exhibiting superior catalytic activity and overpotentials (η) of 298, 267, and 222 mV, respectively at a current density () of -10 mA/cm compared to hexagonal FeP (η = 378 mV) and orthorhombic Fe Mo P (η = 331-459 mV for = 0.12-0.28) catalysts. The highest HER performance was achieved for FeMoP NRs with a dopant composition of 4.58%, consistent with composition-dependent Δ calculations. Although all compositions displayed a Volmer-Heyrovsky HER mechanism, the admixture of Mo improved the HER kinetics, producing the lowest Tafel slope (167.08 mV/dec) for FeMoP NRs. The incorporation of Mo improves the charge transfer resistance and preserves the stability of hexagonal and orthorhombic NRs in alkali environments with a negligible increase in η after 10 h of HER. This study advances the understanding of dopant-induced crystal structure transitions and paves the way for efficient and stable catalytic material design.
电化学水分解是一种可持续的制氢方法，氢气是一种有望替代化石燃料的清洁能源。磷化铁已成为析氢反应（HER）中储量丰富的催化剂，通过混合协同金属制备双金属催化剂可提高其性能。在此，我们报告了一项理论和实验研究，揭示了掺杂剂诱导的六方相向正交相转变对FeP纳米棒（NRs）析氢催化活性和稳定性的影响。在计算研究的八种金属掺杂剂中，Mo因其在FeP（210）表面具有最佳的氢结合自由能（Δ ）而被确定为最有前景的掺杂剂。因此，我们通过胶体合成法制备了平均长度和宽度分别为50.9±22.1至92.4±43.8 nm和3.8±1.0至6.3±1.8 nm的六方和正交Fe Mo P NRs（ = 0 - 14%），以研究其结构和组成依赖性析氢活性。掺入Mo后，当 ≥ 0.11（5.41%）时，底层的六方FeP相转变为正交Fe Mo P。Mo的掺入导致表面化学性质发生变化，从而使Fe和P电荷显著降低。观察到析氢性能既依赖于相又依赖于组成，混合相Fe Mo P NRs（ = 0.03、0.06和0.09）在电流密度（）为 - 10 mA/cm²时表现出优异的催化活性，过电位（η）分别为298、267和222 mV，相比之下，六方FeP（η = 378 mV）和正交Fe Mo P（ = 0.12 - 0.28时η = 331 - 459 mV）催化剂的过电位更高。掺杂剂组成为4.58%的FeMoP NRs实现了最高的析氢性能，这与组成依赖性Δ 计算结果一致。尽管所有组成均显示出Volmer - Heyrovsky析氢机制，但Mo的掺入改善了析氢动力学，FeMoP NRs产生了最低的塔菲尔斜率（167.08 mV/dec）。Mo的掺入提高了电荷转移电阻，并在碱性环境中保持了六方和正交NRs的稳定性，析氢10小时后η的增加可忽略不计。这项研究增进了对掺杂剂诱导的晶体结构转变的理解，并为高效稳定的催化材料设计铺平了道路。
