This review focuses on the discussion of the latest progress and remaining challenges in selected metal-free photocatalysts for hydrogen production. The scope of this review is limited to the metal-free elemental photocatalysts (i.e. B, C, P, S, Si, Se etc.), binary photocatalysts (i.e. BC3, B4C, CxNy, h-BN etc.) and their heterojunction, ternary photocatalysts (i.e. BCN) and their heterojunction, and different types of organic photocatalysts (i.e. linear, covalent organic frameworks, microporous polymer, covalent triazine frameworks etc.) and their heterostructures. Following a succinct depiction of the latest progress in hydrogen evolution on these photocatalysts, discussion has been extended to the potential strategies that are deemed necessary to attain high quantum efficiency and high solar-to-hydrogen (STH) conversion efficiency. Issues with reproducibility and the disputes in reporting the hydrogen evolution rate have been also discussed with recommendations to overcome them. A few key factors are highlighted that may facilitate the scalability of the photocatalyst from microscale to macroscale production in meeting the targeted 10% STH. This review is concluded with additional perspectives regarding future research in fundamental materials aspects of high efficiency photocatalysts followed by six open questions that may need to be resolved by forming a global hydrogen taskforce in order to translate bench-top research into large-scale production of hydrogen.

中文翻译：

---

用于氢析出的无金属光催化剂。

这篇综述着重讨论了用于制氢的精选无金属光催化剂的最新进展和尚存的挑战。本文的范围仅限于不含金属的元素光催化剂（即B，C，P，S，Si，Se等），二元光催化剂（即BC3，B4C，CxNy，h-BN等）及其异质结，三元光催化剂（即BCN）及其异质结，以及不同类型的有机光催化剂（即直链，共价有机骨架，微孔聚合物，共价三嗪骨架等）及其异质结构。在简要描述了这些光催化剂上制氢的最新进展之后，讨论范围扩大到了被认为是获得高量子效率和高太阳能到氢（STH）转换效率所必需的潜在策略。还讨论了可再现性问题以及报告氢气释放速率的争议，并提出了克服这些问题的建议。强调了一些关键因素，可以促进光催化剂从微型生产到大规模生产的可扩展性，以满足目标10％的STH。本文以关于高效光催化剂基本材料方面的未来研究的其他观点作为结尾，随后提出了六个尚待解决的问题，这些问题可能需要组建全球氢气工作组来解决，以便将台式研究转化为大规模生产氢气。强调了一些关键因素，可以促进光催化剂从微型生产到大规模生产的可扩展性，以满足目标10％的STH。本文以关于高效光催化剂基本材料方面的未来研究的其他观点作为结尾，随后提出了六个尚待解决的问题，这些问题可能需要组建全球氢气工作组来解决，以便将台式研究转化为大规模生产氢气。强调了一些关键因素，可以促进光催化剂从微型生产到大规模生产的可扩展性，以满足目标10％的STH。本文以关于高效光催化剂基本材料方面的未来研究的其他观点作为结束的结论，随后是组成全球氢特别工作组以将台式研究转化为大规模生产氢可能需要解决的六个悬而未决的问题。 。