Solar Ammonia Production from Water and Dinitrogen on Metal-Free Carbon NItride Photocatalysts

2021 Fiscal Year Final Research Report

• Project/Area Number: 19H02516
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 27030:Catalyst and resource chemical process-related
• Research Institution: Osaka University
• Principal Investigator: Shiraishi Yasuhiro 大阪大学, 基礎工学研究科, 准教授 (70343259)
• Co-Investigator(Kenkyū-buntansha): 平井 隆之 大阪大学, 基礎工学研究科, 教授 (80208800)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 光触媒 / アンモニア / 半導体 / 空中窒素固定 / 水 / 太陽エネルギー変換

Outline of Final Research Achievements

We had studied the design of metal-free photocatalysts that generate ammonia (NH3) from dinitrogen (N2) and water with high efficiency under visible light irradiation based on the semiconductor graphitic carbon nitride powders. Through three years of research, we had prepared the catalysts based on the following two strategies: (1) the construction of active N2 reduction sites by introducing surface defects, and (2) the introduction of active oxidation sites of water by doping the heteroatoms into the skeleton. We had found that the calcination of precursors with phosphorus pentoxide (P2O5) as a phosphorus source produces the metal-free photocatalysts containing high-concentration phosphorus atoms and surface nitrogen defects. These catalysts successfully generated NH3 with the solar-to-chemical energy conversion efficiency being 0.16%, which is the highest efficiency among the ever reported photocatalysts.

Free Research Field

光化学・光触媒化学

Academic Significance and Societal Importance of the Research Achievements

本研究で開発したNH3合成光触媒は、太陽光を利用して入手容易な原料から水素キャリアをダイレクトに製造する、工業体系を革新する新技術となるほか、新たな人工光合成技術となる可能性がある。それゆえ本研究で得られた成果は、新たなエネルギー製造技術の開発を先導する重要な研究と位置付けることができる。本研究で行った、CNへの窒素欠陥の導入、およびヘテロ元素のドープにより高効率NH3合成を実現した成果は、有機半導体光触媒の開発と高活性化に向けた新たな方法論を導くほか、メタルフリー光触媒による人工光合成研究を牽引する成果と考えられる。