Wu Jiaxiang, Kan Erjun, Zhan Cheng
MIIT Key Laboratory of Semiconductor Microstructure and Quantum Sensing, Nanjing University of Science and Technology, Nanjing 210094, China.
School of Physics, Nanjing University of Science and Technology, Nanjing 210094, China.
Phys Chem Chem Phys. 2024 Nov 20;26(45):28449-28458. doi: 10.1039/d4cp03779k.
Single-atom catalysts (SACs) have shown promising activity in electrocatalysis, such as CO reduction (CORR), the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR). Transition-metal-embedded N-doped graphene (M-N-C) with TM-N active sites (where TM represents a transition metal) is a representative SAC family that has attracted the most attention in both experimental and theoretical studies. However, TM-N type M-N-C has received less attention than TM-N, although some experimental studies have reported its excellent activity in OER and CORR. To fully explore the electrocatalytic activity of TM-N type M-N-C, in this work we systematically investigate the OER and ORR activity of TM-N (TM = Ti, V, Cr, Mn, Fe, Co, Ni, Cu) and TM-NX (X = B, C, O, P) using density functional theory (DFT) calculation. We examine the formation energies, OER/ORR free energy diagrams, overpotentials, charge density, d-band center and electronic structure of each candidate. Our computational screening shows that CuN is a promising bifunctional electrocatalyst for both OER and ORR with low overpotentials of 0.31 V (OER) and 0.44 V (ORR), while CrN and CuNB are predicted to be promising OER catalysts, with overpotentials of 0.26 V and 0.50 V, respectively. A volcano plot derived from the scaling relationships suggests that substituting one nitrogen atom with a hetero atom significantly affects the potential-limiting step in OER/ORR, leading to worse activity in most cases. Density of states and d-band center analyses indicate that the change in OER/ORR activity is strongly correlated with the binding strength of *OH, which is dominated by the location of the d-band center. Our simulation results introduce a comprehensive insight into the activity of the TM-N site in TM-N-C, which could benefit the further development of graphene-based SACs for fuel cells and renewable energy applications.
单原子催化剂（SACs）在电催化领域展现出了良好的活性，例如在一氧化碳还原反应（CORR）、析氧反应（OER）和氧还原反应（ORR）中。具有TM-N活性位点（其中TM代表过渡金属）的过渡金属嵌入氮掺杂石墨烯（M-N-C）是一类具有代表性的单原子催化剂，在实验和理论研究中都备受关注。然而，尽管一些实验研究报道了TM-N型M-N-C在OER和CORR中具有优异的活性，但它受到的关注仍少于TM-N。为了全面探索TM-N型M-N-C的电催化活性，在本工作中，我们使用密度泛函理论（DFT）计算系统地研究了TM-N（TM = Ti、V、Cr、Mn、Fe、Co、Ni、Cu）和TM-NX（X = B、C、O、P）的OER和ORR活性。我们考察了每个候选物的生成能、OER/ORR自由能图、过电位、电荷密度、d带中心和电子结构。我们的计算筛选表明，CuN是一种有前景的双功能电催化剂，用于OER和ORR时过电位较低，分别为0.31 V（OER）和0.44 V（ORR），而CrN和CuNB预计是有前景的OER催化剂，过电位分别为0.26 V和0.50 V。基于标度关系得出的火山图表明，用杂原子取代一个氮原子会显著影响OER/ORR中的电位限制步骤，在大多数情况下会导致活性变差。态密度和d带中心分析表明，OER/ORR活性的变化与OH的结合强度密切相关，而OH的结合强度主要由d带中心的位置决定。我们的模拟结果为深入了解TM-N-C中TM-N位点活性提供了全面的认识，这有助于基于石墨烯的单原子催化剂在燃料电池和可再生能源应用中的进一步发展。
