A review of nanodiamond-based photocatalysts for solar energy conversion

Abstract

Photocatalysis is an important technology for using solar energy to produce hydrogen, convert CO2 to synthetic fuels, and decrease persistent pollutant. However, conventional photocatalysts have limitations, including poor spectral absorption, inefficient charge separation, and structural instability under operational stress, which demand innovative durable materials with tailored electronic properties. Nanodiamond (ND) has recently been recognized as a suitable material because of its exceptional chemical stability, superior charge carrier mobility, and possible surface functionalization. While its intrinsic wide bandgap limits its response to visible-light, different methods have been demonstrated to activate its catalytic potential. Here, several emerging strategies for improving the catalytic performance of ND-based photocatalytic systems are summarized, including surface functionalization, plasmonic hybridization, heteroatom doping, and heterostructure design. And the structure-activity relationship and design principle are proposed to improve the light harvesting, charge transport, and redox kinetics for constructing high efficiency ND-based photocatalysts used in the renewable energy and environmental industries.

1. Introduction

The direct and effective utilization of solar energy has become a key component of sustainable fields, such as photocatalysis, thermal catalysis, photovoltaic and photothermal power generation[1–3]. Photocatalysis, which mimics natural photosynthesis by leveraging semiconductors to drive redox reactions under light irradiation, has emerged as a cornerstone technology for solar energy cycles[4–8]. Its applications span 3 critical domains: (1) solar water splitting for hydrogen production[9–13]; (2) CO2 photoreduction to value-added hydrocarbons[14–18]; (3) environmental remediation via radical-mediated pollutant degradation[19–21]. The International Energy Agency asserts that hydrogen and hydrogen-based fuels play a pivotal role in achieving net-zero emissions.

Unfortunately, traditional semiconductor photocatalysts face multiple key challenges due to their inherent limitations in practical applications. Most photocatalysts possess wide band gap (Eg), rendering them capable of excitation solely by ultraviolet (UV) or near UV light. For example, ZnO (3.3 eV) and TiO2 (3.2 eV) have wide bandgaps, and can utilize only 4% of the solar energy in the UV[22–23]. While doping (e.g., N, S) or defect engineering can extend the absorption edge into the visible region[24], such modifications frequently result in an augmentation of carrier recombination centers, consequently diminishing quantum efficiency. Furthermore, the energy conversion efficiency is severely constrained by inadequate charge separation, electron–hole recombination and slow transport, as well as sluggish interfacial reactions. Meanwhile, concerns regarding thermal, hydrothermal, and chemical stability have the potential to jeopardize the photocatalytic lifetime, a predicament in practical applications. Additionally, the presence of toxic deactivation in photocatalysts represents a critical defect in photocatalytic applications[25]. These limitations necessitate advanced materials with broad light absorption, efficient charge separation, and robust stability.

Nanodiamond (ND) has arisen as a revolutionary catalytic platform, uniquely positioned to overcome conventional semiconductor limitations through distinguished structural and electronic properties[26]. As prototypical zero-dimensional carbon nanomaterials (diameter of 1–100 nm), NDs feature a sp3-hybridized tetrahedral lattice that confers remarkable core properties.