Ferro-, piezo-, and pyroelectric materials are emerging as potential candidates for converting various forms of primary energy from the ambient environment (e.g., sunlight, mechanical, and thermal energy) into secondary energy (e.g., chemical energy). Despite the relatively short investigation time, much progress has been made related to this field. This review covers the fundamental principles of coupling ferro-, piezo-, and pyroelectric effects with different catalytic reactions; the crucial role of a polarization-induced internal electric field in charge separation and transport in these materials is discussed. We particularly focus on recent notable examples of using these three types of nanostructured materials for a variety of catalytic applications in the fields of renewable energy production (e.g., water splitting and CO 2 reduction), environmental remediation (e.g., organic pollutant decontamination), and materials synthesis (e.g., selective growth/deposition and organic synthesis). Finally, we conclude this review by proposing critical challenges and future perspectives for developing ferro-, piezo-, and pyroelectric nanomaterial-based catalysts for efficient energy harvesting.

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Zhao et al. Reply In the first sentence of the Comment [1], the authors refer to four systems: GaNð10 10Þ-1H, ZnOð10 10Þ-1H, GaNð10 10Þ-Li, and ZnOð10 10Þ-1Li. In the second sentence, the authors claim to demonstrate that "a charge-density-wave (CDW) phase is due to the artifact of the generalized gradient approximation (GGA), while the antiferromagnetic (AFM) ground state is predicted by the hybrid DFT calculation…" The Comment contains a single table, showing the total energy of the GaNð10 10Þ-1H system only. No numerical results were presented for the other three systems. It is not clear how the authors arrived at their very general conclusion.We have checked the validity of Kim et al.'s claim by performing new calculations using two popular hybrid functionals, HSE06 [2,3] and B3LYP [4], on the four systems mentioned in the Comment. These two hybrid functional methods are generally considered to be at the same level of accuracy. All hybrid functional calculations are performed on a 12-layer slab separated by a 12 Å vacuum. The two-dimensional k grid of the Brillouin zone is 8 × 6 for the pð1 × 1Þ cell and the same density is used for larger cells. The results are listed below.Based on these results, we draw a few observations: (i) For the GaNð10 10Þ-1H system, different hybrid functionals produce different ground states. The conclusions are not consistent. Our Table I shows that the B3LYP hybrid method favors the CDW state by 0.21 eV per pð2 × 2Þ unit cell, and that this preference is reversed with the HSE06 hybrid method, which instead favors the AFM state by 0.06 eV. This is similar to Kim's HSE results, which also favored the AFM state by 0.07 eV. Importantly, Kim et al. also perform RPA calculations, which favor the AFM state by 122 meV per pð2 × 2Þ unit cell in GaN-1H. We have confirmed this value for RPA. For the GaNð10 10Þ-1Li system, however, both hybrid functionals B3LYP and HSE06 favor the CDW ground state, by 0.5 and 0.25 eV, respectively. For GaNð10 10Þ-1Li, we have also carried out RPA calculations [5-8] using a four-layer slab. The RPA results favor the CDW state over the AFM state by 0.16 eV. Thus, for GaNð10 10Þ-1Li, all results using B3LYP, HSE06 and RPA support our findings [9], and disagree with the claim of Kim et al. (ii) For ZnOð10 10Þ with 1H and 1Li, both HSE06 and B3LYP functionals favor the CDW ground state, according to our new results shown