image: a, Photothermal effect in photo-involved catalytic reactions. ΔT is the photo-induced temperature increase at catalyst interface and Δ λ is the wavelength shift of cladding mode resonance. b, Optical fiber sensing principle and system for operando monitoring light-to-heat at liquid-solid catalyst interface. view more
Credit: by Zhi Li, Yongguang Xiao, Fu Liu, Xiangyu Yan, Daotong You, Kaiwei Li, Lixi Zeng, Mingshan Zhu, Gaozhi Xiao, Jacques Albert and Tuan Guo
Solar-to-chemical energy conversion through photocatalysis or photo-electrocatalysis is one of the most attractive solutions to deal with the current energy crisis and global warming. As for the photo-involved catalytic reactions, photothermal effect is happening on the surface of the catalyst, which in turn drives the catalyst’s microscopic reactions and influences the structure-activity relationships of catalyst. In order to understand the correlation between thermal effects and photo-involved catalytic processes, in situ measuring the local temperature (i.e., at the catalyst surface) could provide new evidence about the intrinsic properties of photo-electrocatalysis process.
To address this, simple-to-implement CNT/gold coated tilted fiber Bragg gratings exciting narrow-band spectral comb is developed, in which CNT/gold coating layer allows for distinguishing measurements of bulk temperature in reactor (fundamental mode) and local temperature on the metal surface (high order cladding modes with high sensitivity to the metal temperature) without disturbing the photo-electrocatalytic reactions. A thermal resolution of 0.1 oC, a temporal resolution of 0.1 s is achieved by light-to-heat-to-surface temperature variation at liquid-solid catalyst interface. Moreover, a stable and reproducible correlation between light-to-heat and catalytic activities has been tested real-time for two photo-activated electrochemical processes (i.e., electro-oxidation of ethanol and electro-detection of acetaminophen (APAP)). Surface temperature measurements revealed a diffusion-controlled process of electro-oxidation (linear dependence of surface temperature) and a surface-controlled process for electro-detection (nonlinear relationship between electrocatalytic activity and light-to-heat generated temperature). This fundamental understanding thus is an example of the benefits provided by metal-coated tilted fiber Bragg grating optical fiber sensor in operando for electro-chemical sensing systems and eventually in deployed catalytic power plants.
While the interrogation tools herein include expensive instruments which are incompatible with widespread facilities monitoring power plants with a large number of photo-catalytic electrodes, the coming work is to develop customized, multiplexed laser diode-based interrogation systems compatible with products in market. Finally, accurate multi-point temperature measurements and mapping is prerequisite for the interpretation of photo-involved catalytic reactions, which is promising to improve the efficiency, reliability and cost-effectiveness and thus helps to make progress in terms of the usage of solar energy.
Journal
Light Science & Applications