Modulating the Oxidation State of Titanium via Dual Anions Substitution for Efficient N₂ Electroreduction

Abstract

The electrocatalytic nitrogen reduction reaction (NRR) is a promising approach for renewable ammonia synthesis but remains significantly challenging due to the low yield and poor selectivity. Herein, a facile N and S dual anions substitution strategy is developed to tune the Ti oxidation states of TiO2 nanohybrid catalyst (NS‐TiO2/C), in which anatase TiO2 nanoplates with dense Ti3+ active sites are uniformly dispersed on porous carbon derived from 2D Ti3C2Tx nanosheets. The catalyst NS‐TiO2/C exhibits a superior ambient NRR efficiency with an NH3 yield rate of 19.97 µg h−1 mg−1cat and Faradaic efficiency of 25.49% and is coupled with a remarkable 50 h long‐term stability at −0.25 V versus RHE. Both experimental and theoretical results reveal that the N and S dual‐substitution effectively regulate the Ti oxidation state and electronical properties of the NS‐TiO2/C via simultaneously forming interstitial and substitutional TiS and TiN bonds in the anatase TiO2 lattice, inducing oxygen vacancies and dense Ti3+ active species as well as better electronic conductivity, which substantially facilitates N2 chemisorption and activation, and reduces the energy barrier of the rate‐determining step, thereby essentially boosting NRR efficiency. This work provides a valuable approach to the rational design of advanced materials by modulating oxidation states for efficient electrocatalysis.

Unveiling Spin State‐Dependent Micropollutant Removal using Single‐Atom Covalent Triazine Framework

“…The prepeak at 4971 eV is attributed to the quadruple‐allowed Ti 1s–3d electronic transitions, which is a typical feature of noncentral symmetry. [ 33 ] In the Fourier transform of the extended X‐ray absorption fine structure (EXAFS), no peaks related to TiO coordination (1.49 Å) and TiTi coordination (2.51 Å) are observed in Ti 1 N 3 /CTF‐10 (Figure 2c). Instead, light element bonding such as TiN or TiC first coordination shell is detected at 1.09 Å.…”

First-principles screening of transition metal doped anatase TiO2(101) surfaces for the electrocatalytic nitrogen reduction

“…5 For the eNRR, non-metal element (C or B) doped anatase TiO 2 exhibited an efficiency several times higher than that of defect-containing TiO 2 , although the mechanism for the enhancement is not clear 11,12 N and S co-doping significantly boosts the performance. A faradaic efficiency of 25.49% at À0.25 V RHE was reached, 13 which was attributed to the high density of Ti 3+ species and the improved electronic conductivity. For transition metal doping, Zheng et al found that the doping of Zr in anatase TiO 2 promotes the formation of O v sites, which deliver an excellent performance with a high ammonia production rate and a faradaic efficiency of 17.3% at À0.45 V RHE .…”

Unifying the Nitrogen Reduction Activity of Anatase and Rutile TiO2 Surfaces

“…[16,18] Recently, TiO 2 has also attracted more and more attention as an electrocatalyst for nitrogen reduction. [19][20][21][22][23][24][25][26][27][28][29][30] It was shown that oxygen vacancy created via in situ electrolysis is active for NRR. [19] Engineering the oxygen vacancy by doping becomes a popular strategy for designing TiO 2 -based electrocatalytic NRR catalysts.…”

“…[19] Engineering the oxygen vacancy by doping becomes a popular strategy for designing TiO 2 -based electrocatalytic NRR catalysts. For example, Zheng et al found that Zr doping can cause strain in the TiO 2 slab which promotes the formation of bi-Ti 3 + species which exhibited a Faraday efficiency of 17.3 % for NRR at À 0.45 V. [22] Carbon, [28,29] Copper, [26,27] Pd, [23] and Vanadium [21] doped TiO 2 showed similar performance; while Fe doping [24,25] or dual anion [30] doping further enhance the Faraday efficiency to about 22-26 %. These works suggest that TiO 2 is a promising candidate for electrocatalytic NRR.…”

“…Recently, TiO 2 has also attracted more and more attention as an electrocatalyst for nitrogen reduction [19–30] . It was shown that oxygen vacancy created via in situ electrolysis is active for NRR [19] .…”