A Carbon‐Free and Free‐Standing Cathode From Mixed‐Phase TiO₂ for Photo‐Assisted Li–CO₂ Battery

Abstract

Li–CO2 battery provides a new strategy to simultaneously solve the problems of energy storage and greenhouse effect. However, the severe polarization of CO2 reduction and CO2 evolution reaction impede the practical application. Herein, anodic TiO2 nanotube arrays are first introduced as carbon‐free and free‐standing cathode for photo‐assisted Li–CO2 battery, and the photo‐assisted charge and discharge mechanism is first clarified from the perspective of photocatalysis. Mixed‐phase TiO2 exhibits a long cycling life of 580 h (52 cycles) at 0.025 mA cm−2 and delivers a high discharge specific capacity of 3001 µAh cm−2 under UV illumination. The charge voltage dramatically reduces from 4.53 to 3.03 V under UV illumination. The improvement of photo‐assisted Li–CO2 battery performance relies on the synergistic effect of the hierarchical porous structure, strong UV absorption, efficient separation, and transfer of photo‐generated electrons and holes at hetero‐phase junction, and the facilitation of photo‐generated electrons and holes on CO2 reduction and CO2 evolution reaction. This work can provide useful guidance for designing efficient photocathode for photo‐assisted Li–CO2 battery and other metal–air batteries.

Type-II heterojunction photocathode for CO2 reduction and light-assisted metal–CO2 batteries

“…289 mV dec −1 for the TiO 2 /CC electrode) for the Li–CO 2 battery. 15,17 Meanwhile, we propose for the first time to quantify the actual contribution of the introduction of illumination to CO 2 conversion by calculating the efficiency of solar-to-carbon ( η STC ) conversion through the following equation: 43 where j ph is the photocurrent density of the device, 2.80 V is the electromotive force for the conversion of CO 2 into reduction products (C/Li 2 CO 3 ) and P in is the power of incident illumination, taken as 100 mW cm −2 for the AM 1.5 G spectrum with 1 sun intensity. The corresponding STC efficiency of the Li–CO 2 device was determined to be 1.19%.…”

“…Several strategies have been proposed to ameliorate the slow kinetics and the large overpotential for light-assisted metal–CO 2 batteries, including synthesis of high-efficiency bi-functional cathode catalysts, 15–18 the synergy of multi-field effects, 19,20 and the design of catalyst structures. 21,22 For example, Wang et al prepared a phthalocyanine-based metal–organic framework nanosheet with dual active metal sites (CoPc–Mn–O).…”

A Li–O2/CO2 battery based on bio-inspired engineering of the Bi2S3/PVP cathode

“…Commercial carbon materials KB and Super P were first used as cathode catalysts for Li-CO 2 batteries. [26][27][28] However, the catalytic activity of commercial carbon materials is limited. To improve their performance, some noble and transition metal-based materials have attracted much attention due to their excellent catalytic activity.…”

High‐Rate Nonaqueous Mg–CO2 Batteries Enabled by Mo2C‐Nanodot‐Embedded Carbon Nanofibers

“…To improve catalytic efficiency and accommodation of discharge product deposition, it is crucial to optimize the cathodic architecture. [34][35][36][37][38][39][40][41][42] To achieve this, the cathode's structure must possess three essential attributes: 1) nanosized catalyst materials-these materials should have a large surface area while preventing agglomeration within the cathode to enhance catalytic active sites; 2) conductive network-an extensive conductive network with ample surface area should be in place to facilitate efficient redox reactions; 3) macroporous structurethe cathode should feature a macroporous design to accommodate the deposition of discharge products effectively.…”