Dual-functional photocatalysts for in-situ generation of proton (H+) and photoreduction of carbon dioxide (CO2): A review

To date, the question of how to address the challenges associated with urgent global carbon emissions while harnessing renewable energy remains unanswered, a challenge that our world has so far failed to solve. Among many strategies, artificial photosynthesis systems that mimic natural processes to enable the in-situ generation of protons (H + ) for hydrogenation of CO 2 into value-added carbonaceous fuels represent a promising route. Herein, this review highlights recent advancements in solar-driven photoreduction of CO 2 in the presence of H + . Emphasis is placed on photocatalysts and their fundamental mechanisms governing the photoreduction of CO 2 , including light absorption, charge-carrier dynamics, surface adsorption, and photocatalytic efficiency. The concept of dual-functional photocatalytic active CO 2 via in-situ generation of H + provides a sustainable and carbon-neutral pathway to produce renewable energy. Although many efforts have been made, the overall energy conversion efficiency remains limited by the complexity of multistep reactions, rapid electron-hole recombination rates, and low quantum efficiencies. This review critically examines the key technical challenges and current strategies for further improving solar-to-fuel efficiency, with a focus on developing novel photocatalysts. Additionally, combining photocatalysis with biocatalysis, electrocatalysis, photoelectrochemical architectures, or membrane-assisted processes may enable the practical applications of artificial photosynthesis and help bridge the efficiency gap between lab-scale to industrial-scale. • Artificial photosynthesis enables in-situ protons (H + ) generation for CO 2 hydrogenation • Key challenges and strategies to improve solar-to-fuel efficiency • Focus on designing advanced, high-performance photocatalysts • Hybrid systems (photo-, bio-, electro-) enable practical CO 2 conversion applications