第一作者：王昭晖
通讯作者：陈咏梅
通讯单位：北京化工大学
论文DOI：10.1002/adfm.202425301
阴阳极耦合电化学系统通过阳极的水氧化（2e-WOR）和阴极的氧还原（2e-ORR）同步生成过氧化氢（H2O2），为传统的蒽醌工艺提供了一种先进的替代方法。然而，这种耦合系统的效率往往受限于电催化剂活性和选择性。该工作报道了一种嵌入在空心介孔碳球中的无定形二氧化钛（TiOx@MCHS）双功能催化剂，它对2e-WOR和2e-ORR均表现出优异的电催化性能。以4 M K2CO3/KHCO3为电解质的无膜流动池中同时使用TiOx@MCHS负载电极作为阳极和阴极，在240 mA的恒电流条件下（阳极：1 cm2，阴极：4 cm2），实现了H2O2的高效生成（速率达到108.3 μmol min−1 cm−2，法拉第效率为~145%，槽压仅~2.5 V）。实验和计算结果揭示了低配位钛原子在优化两个电极反应途径所涉及的中间产物吸附方面的关键作用，从而提高了活性和选择性。
过氧化氢（H2O2）作为一种无有害副产物的绿色氧化剂，在化工合成、环境保护及医疗消毒等领域需求激增。当前主流的蒽醌法存在高浓度H2O2储运风险，而电化学合成技术因其温和反应条件与环境友好特性备受关注。电化学方法可以在阴极通过氧气的两电子还原（2e-ORR），或者在阳极通过水的两电子氧化（2e-WOR）反应实现H2O2生成。耦合这两种途径，理论上可实现200%的法拉第效率，但面临双重挑战：现有2e-WOR催化剂活性不足导致电流密度受限；阴阳极需不同电解液迫使采用复杂隔膜体系。
受限于2e-WOR苛刻的工作电位和氧物种吸附能的要求，金属氧化物几乎是2e-WOR催化剂的唯一选择；幸运的是，金属氧化物同样适用于2e-ORR，从而为双功能催化剂的开发提供了机会。其中，二氧化钛（TiO2）具有宽电位窗口和良好稳定性，但其∗OH吸附能过高、导电性差等问题制约其催化性能。
1. 通过构建无定形TiO2增加缺陷位点调控氧中间体吸附能。
2. 以空心介孔碳球作为载体，有效提高了催化剂的电子传输和质量传递速率。
3. 理论和实验揭示了不饱和配位的Ti原子在调控中间体吸附自由能方面起到了重要作用，从而赋予了无定形TiO2卓越的双功能活性。
4. 使用双功能催化剂，实现了在无隔膜电解池中阴阳极同时高效生成H2O2。
Scheme1. The synthetic scheme of TiOx@MCHS.
Figure 1. Characterization of TiOx@MCHS. The SEM image (a) and TEM image (b) of TiOx@MCHS. (c) The EDS element mapping and corresponding high-angle annular dark Field (HAADF) image of TiOx@MCHS. (d) The N2 adsorption-desorption isotherm of TiOx@MCHS and the BJH desorption dV/dD pore volume plot (inset image). (e) XRD patterns of TiOx@MCHS and MCHS. (f) The AC-TEM image of TiOx@MCHS. The XPS survey (g), Ti 2p spectra (h) and O 1s spectra (i) of TiOx@MCHS.
Figure 2. Electrochemical performance on 2e-WOR. (a) Schematic diagram of experiment setup used for 2e-WOR. (b) LSV curves of different catalysts obtained in 1 M Na2CO3 at a potential scanning rate of 5 mV s–1. (c) The Tafel slopes of different catalysts calculated from the LSV curves. The FEs (d) and generation rates (e) for H2O2 of different catalysts as a function of potential tested in 1 M Na2CO3. (d) The current densities of different catalysts under different scan rates and corresponding Cdl. (g) The WOR H2O2 FEs and production rates for H2O2 on TiOx@MCHS at different potentials performed in a 3.5 M K2CO3 and 0.5 M KHCO3 solution. (h) The LSV curves of TiOx@MCHS before and after 4 h electrolysis under 2.6 V in a 3.5 M K2CO3 and 0.5 M KHCO3 solution. (i) Performance comparison of different 2e-WOR catalysts.
Figure 3. Electrochemical performance on 2e-ORR. (a) The RRDE LSV curves of catalysts at 1600 rpm in O2-saturated 0.1 M KOH electrolyte with a potential scanning rate of 5 mV s–1. (b) The Tafel slopes of catalysts derived from the LSV curves. (c) The EIS plots of catalysts at half-wave potential in O2-saturated 0.1 M KOH with an electrode rotation rate of 1600 rpm. (d) The H2O2 selectivity and electron transfer number of catalyst calculated from RRDE LSV curves. (e) The LSV curves of TiOx@MCHS at 1600 rpm in O2-saturated Na2CO3 electrolyte with different concentrations. (f) The LSV curves of TiOx@MCHS at 1600 rpm in O2-saturated 1 M KOH electrolyte with the addition of different concentrations of carbonate (+0.02 M carbonate means the addition of 0.01 M Na2CO3 and 0.01 M NaHCO3). (g) The schematic diagram of the cell device for H2O2 electrosynthesis via 2e-ORR. The ORR H2O2 production rates (h) and FEs (i) for H2O2 on TiOx@MCHS at different potentials performed in a 1 M KOH or 3.5 M K2CO3+0.5 M KHCO3 solution.
Figure 4. DFT calculations of amorphous TiO2 toward 2e-ORR and 2e-WOR. The schematic diagram of H2O2 generation mechanism on amorphous TiO2 surface through water oxidation (a) and oxygen reduction reaction (b). The free energy diagram on the best active site for WOR (c) and ORR (d).
Figure 5. Performance in coupled 2e-WOR//2e-ORR flow cell. (a) The schematic diagram of the composition of the 2e-WOR//2e-ORR cell. (b) The H2O2 FEs, generation rates and the total voltages of the 2e-WOR//2e-ORR cell at constant currents. (c) The FEs, generation amounts of H2O2 and the cell voltages during long-term stability test at 120 mA (anode current density: 120 mA cm–2). (d) The comparison on catalytic performance. (e) The comparison on cell performance. All production rates for H2O2 are calculated based on geometric area of anode.
该工作成功构建了基于无定形TiO2嵌入介孔碳空心球（TiOx@MCHS）的双功能电催化剂，实现了2e-WOR与2e-ORR的高效耦合。理论计算揭示，TiOx@MCHS中不饱和配位的Ti位点通过双重调控机制显著提升催化性能：一方面优化2e-ORR过程中*OOH中间体吸附自由能，另一方面促进2e-WOR中*OH中间体耦合动力学。结合介孔空心碳骨架的快速传质优势，该催化剂在单一碳酸盐电解液中实现了108.3 μmol min−1 cm−2的H2O2生成速率及145%的法拉第效率，同时槽电压低至2.5 V（恒电流240 mA）。该研究不仅为2e-WOR//2e-ORR双功能催化剂微观结构设计提供了新的思路，更通过无膜流动电解槽的示范应用，展示了H2O2连续电合成技术的工业化潜力。
Wang, Z.; Li, K.; Hu, J.; Li, A.; Tang, Y.; Sun, Y.; Wan, P.; Jiang, H.; Chen, Y. Dual-Functional Catalyst of Amorphous TiO2 Embedded in Mesoporous Carbon Hollow Spheres for H2O2 Electrosynthesis. Adv. Funct. Mater. 2025, n/a (n/a), 2425301.
https://doi.org/10.1002/adfm.202425301
欢迎关注我们，订阅更多最新消息
“邃瞳科学云”推出专业的自然科学直播服务啦！不仅直播团队专业，直播画面出色，而且传播渠道多，宣传效果佳。
“邃瞳科学云"平台正在收集、整理各类学术会议信息，欢迎学会、期刊、会议组织方择优在邃瞳平台上进行线上直播，希望藉此帮助广大科研人员跨越时空的限制，实现自由、畅通地交流互动。欢迎老师同学们提供会议信息（会有礼品赠送），学会、期刊、会议组织方商谈合作，均请联系18612651915（微信同）。
投稿、荐稿、爆料：Editor@scisight.cn
