Solar Photocatalysis

Rapid growth in economy and society currently relies on fossil fuels heavily, leading to serious concern on energy sustainability and environmental pollution. This has aroused increasing interest in solar energy, which is the most abundant and green energy source. However, it remains a significant challenge in storing and harnessing solar energy due to its diurnal and seasonal fluctuation along with uneven distribution. Moreover, its energy density is relatively low; and the energy supply from traditional solar cells is time-varying. Consequently, it is difficult to synchronize the generation and usage of electricity from solar cells. In contrast, photocatalytic water splitting can convert solar energy to chemical energy, which can be stored in the form of hydrogen, an ideal energy carrier that is characteristic of cleanness and operational convenience. Also, photocatalytic CO2 reduction can transform greenhouse gas to valuable fuels. Furthermore, photocatalytic degradation of organic pollutants can decontaminate air, water, and soil. Additionally, photocatalytic disinfection and sterilization can reduce human exposure to pathogens and toxins. Therefore, photocatalysis has received extensive attention globally, becoming the hotspot and frontier across several fields, including chemistry, materials science, energy and environment engineering. In this special issue (Part 1), 2 progress reports, 12 review articles and 15 research articles have been published. Classified based on applications, 8 papers concern with hydrogen evolution, 7 papers involve CO2 reduction, 2 articles deal with pollutant decomposition, and 11 papers are related to nitrate reduction, nitrogen fixation, organic synthesis, syngas synthesis, NADH (nicotinamide adenine dinucleotide) regeneration and so on. From the materials perspective, 8 papers discuss C3N4, 4 articles involve CdS, 3 paper concern with conjugated polymers, other papers cover TiO2, CdSe, CoMn alloy, PbI2/CuI, silicon, metal-organic frameworks (MOFs), perovskite oxides, Bi2MoO6 and so on. Photocatalytic H2 production is of great interest from both theoretical and practical viewpoints because of its potential application in converting solar energy into storable chemical energy. Herein, Zhen and Xue (solr.202000440) have reviewed surface functionalization of polymeric carbon nitride at atomic and molecular levels for photocatalytic H2 production and CO2 reduction applications. Then, Yu et al. have (solr.202000372) reported enhanced photocatalytic H2 production activity of g-C3N4, which are prepared by one-step crystallization and cyano-group modification. Yang and co-workers (solr.202000414) have presented the fabrication of 2D/2D CdS/MXene Schottky heterojunctions by electrostatic self-assembly and solvothermal method and their application in high-efficiency photocatalytic hydrogen production. Tang and colleagues (solr.202000281) have reported the molecular cobalt catalysts grafted on a conjugated microporous polymer for high-efficiency H2 production. Zhao et al. (solr.202000415) have prepared a CdS/MoS2 nanooctahedron heterostructure with a tight interface for enhanced photocatalytic H2 evolution and biomass upgrading. Wu's group (solr.202000474) have reported a per-6-thiol-cyclodextrin engineered [FeFe]-H2ase mimic/CdSe quantum dot assembly for effective photocatalytic H2 evolution. Xu et al. (solr.202000486) have synthesized a lignin-modified g-C3N4 nanoarchitecture with an ultrathin layered topography for efficient photocatalytic H2 production. Finally, Kwon et al. (solr.202000411) have reported a self-assembly between the CdS quantum dots and the RuO2/reduced graphene oxide nanosheets, showing enhanced photocatalytic H2 production activity. Nowadays, there is increasing interest in solutions to the increasing CO2 level in the atmosphere. Photocatalytic reduction of CO2 into storable solar fuels is an appealing strategy to simultaneously overcome both environmental problems and energy crisis. In this special issue, Wang's group (solr.202000443) has firstly discussed the active sites of catalysts for CO2 activation and conversion. Then, Liang et al. (solr.202000478) have summarized recent research progress in g-C3N4 and its composite photocatalysts for CO2 reduction. Huang's group (solr.202000430) has reviewed junction engineering for photocatalytic and photoelectrocatalytic CO2 reduction. Zhang et al. (solr.202000387) have demonstrated an all-earth-abundant photothermal silicon platform for CO2 catalysis with nearly 100% sunlight absorption ability. Jia's group (solr.202000313) has reported anchoring single-atom Ru on CdS, showing enhanced CO2 capture and charge accumulation for highly selective photothermocatalytic CO2 reduction to solar fuels. Xiang et al. (solr.202000351) have prepared an ultrathin S-scheme heterojunction based on few-layer g-C3N4 and monolayer Ti3C2Tx MXene for photocatalytic CO2 reduction. Finally, Zhang's group (solr.202000326) has reported an ultraviolet-visible-near-infrared responsive Cu2-xS/g-C3N4 composite photocatalyst and its photocatalytic CO2 reduction performance. It worth noting that significant efforts have been made to prepare high-performance photocatalysts for environment remediation including air purification, hazardous waste removal, water purification, and etc. Herein Xu et al. (solr.202000416) have fabricated a g-C3N4/NH2-UIO-66 composite photocatalyst with enhanced photocatalytic removal efficiency for hexavalent chromium. Zhu's group (solr.202000453) has reported the enhanced photocatalytic phenol degradation activity in the presence of g-C3N4/PDI (perylenetetracarboxylic diimide). Janáky and co-workers (solr.202000418) have reported the preparation of PbI2/CuI nanocomposite electrode and its solar photoelectroreduction of nitrate ions. Peng's group (solr.202000487) has summarized updated research progresses in photocatalytic nitrogen-fixation reaction over semiconductors. Su and colleagues (solr.202000444) have surveyed recent advance in the rational harnessing of photoexcited hole-electron pairs in semiconductor photocatalysts, and the application in oxidative and reductive synthetic transformations for chemical and pharmaceutical production. Ouyang's group (solr.202000488) has reported the fabrication of CoMn alloy using a metal-segregation method and its enhanced photothermal conversion of syngas to light olefins. Qian and Zhang (solr.202000489) have commented the recent advance in the conjugated microporous polymers in visible light promoted chemical transformations such as water splitting, CO2 reduction, organic photoredox reactions, and etc. Chen and colleague (solr.202000442) have reviewed the current research status of Bi2MoO6-based photocatalysts and their surface/interface modification strategies and applications. Dong and co-workers (solr.202000419) have reviewed the synthesis strategy, interfacial effect and photocatalytic application of perovskite nanocrystals-based heterostructure photocatalysts. Hao and Li (solr.202000454) have reviewed visible-light initiated synergistic/cascade reactions over metal-organic frameworks. Ma's group (solr.202000397) has highlighted the 2D/2D Z-Scheme heterojunctions for photocatalytic application. Wang et al. (solr.202000392) have reviewed two-dimensional silicon (2D Si) for catalysis and photocatalysis applications. Liu's group (solr.202000339) has summarized the key developments of conjugated photocatalytic systems for NADH (nicotinamide adenine dinucleotide) regeneration. As the guest editors, we thank all the authors for their prompt response to the paper call and their valuable contribution to this special issue. All the manuscripts were refereed through rigorous peer-review processes. We greatly appreciate the timely and conscientious evaluation of manuscripts by the reviewers. Last but not least, we are grateful to Dr. Lulu Ma, Editor of Solar RRL, for her tremendous support and dedication. Jiaguo Yu received his B.S. and M.S. in chemistry from Central China Normal University and Xi'an Jiaotong University, respectively; his Ph.D. in Materials Science from Wuhan University of Technology (WUT). In 2000, he became a Professor at WUT. His research interests include photocatalysis, adsorption, supercapacitor, electrocatalysis, formaldehyde removal and so on. He is Foreign Member of Academia Europaea (The Academy of Europe) (2020), Foreign Fellow of the European Academy of Sciences (2020) and Fellow of the Royal Society of Chemistry (2015). Tierui Zhang is currently Professor at the Technical Institute of Physics and Chemistry, Chinese Academy of Sciences. He obtained his Ph.D. degree in Chemistry from Jilin University, China in 2003. He worked as a postdoctoral fellow in the labs of Prof. Markus Antonietti, Prof. Charl F.J. Faul, Prof. Hicham Fenniri, Prof. Z. RyanTian, Prof. Yadong Yin, and Prof. Yushan Yan. His current scientific interests focus on catalyst nanomaterials for energy conversion. Nianqiang Wu is currently Armstrong-Siadat Endowed Professor in Materials Science at University of Massachusetts Amherst, USA. He has received his Ph.D. degree in Materials Science and Engineering from Zhejiang University, China. Dr. Wu is Fellow of the Electrochemical Society (FECS) and Royal Society of Chemistry (FRSC). His research interest lies in: 1) photocatalysts and photoelectrochemical cells, 2) electrochemical energy storage, and 3) biosensing, microfluidics and photodynamic therapy.