Abstract
An emerging design heuristic for electrochemical nitrate reduction (NO3RR) catalysts is synthesizing electron-deficient sites to facilitate binding of electron-rich NO3–. However, this rule has rarely been applied to metal-, nitrogen-doped carbon (MNC) catalysts. Titanium (Ti), with low electronegativity and high NO3RR reactivity, is a compelling MNC candidate. To date, atomically dispersed TiNxmotifs have eluded synthesis due to the strong oxophilicity of Ti. Here, we leverage nitrogen-rich carbon flowers (CF) to overcome synthetic challenges and produce Ti-, N-doped carbon flower (TiCF) catalysts. Advanced materials characterization demonstrates that TiCF catalysts are a mixed phase material with 3/4 of Ti atoms in TiO2-like nanoparticles and 1/4 of Ti atoms in novel, atomically dispersed TiNxsites. TiCF achieves 61 ± 7% NH3-selectivity at −0.70 V vs RHE and 14 ± 5 mA/cm2to NH3formation (|jNH3|) at −0.85 V vs RHE in (0.1 M NaOH + 0.1 M NaNO3+ 0.45 M Na2SO4) electrolyte. Control studies show both CF morphology and Ti sites are essential for high NO3RR activity. Density functional theory calculations attribute the NO3RR reactivity to TiNx, which facilitates multiple bond formation with surface intermediates to promote favorable NH3synthesis pathways. Thus, TiCF exhibits 60× higher |jNH3| values than bulk Ti and NH3yield rates (>0.06 mmol NH3/h/cm2) that are competitive with state-of-the-art MNC catalysts (e.g., FeNC, CuNC). TiCF introduces a new class of Ti electrocatalysts, advancing the MNC design space and sustainable NH3production.
| Original language | English |
|---|---|
| Pages (from-to) | 29026-29041 |
| Number of pages | 16 |
| Journal | Journal of the American Chemical Society |
| Volume | 147 |
| Issue number | 32 |
| DOIs | |
| State | Published - Aug 13 2025 |
Funding
This research was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division, Catalysis Science Program to the SUNCAT Center for Interface Science and Catalysis. Additional support was also provided by the National Science Foundation EFRI program (2132007), the Dreyfus Foundation Teacher-Scholar Award (TC-22-093), and the Chemical Engineering Department at Stanford University. M.J.L. acknowledges support from the National Aeronautics and Space Administration (NASA) Space Technology Graduate Research Opportunities fellowship (80NSSC20K1207) and the Northern California Chapter of the ARCS Foundation (Rhoda Goldman Memorial Scholarship). C.A.F.O. was supported by the DARPA FAARM program (Award HR0011-25-3-0309). The authors would like to acknowledge the use of the m2997 computer time allocation at the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The transmission electron microscopy portion of this research was supported by the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. Part of this work was performed at the Stanford Nano Shared Facilities (SNSF), supported by the National Science Foundation under award ECCS-2026822. The authors thank Jinyu Guo and Qianhong Zhu for support collecting Ti K-edge XAS measurements of TiCF (0.1 wt %). The authors additionally thank the Tarpeh, Jaramillo, and Bao groups for critical feedback on the project.