No abstract

No abstract

No abstract

Low-grade metallurgical silicon (MG-Si, purity ∼98%−99%, $1/kg) with annual production over six million tons is an attractive feedstock to produce active photocatalysts. However, MG-Si is known as an electronically dead material due to serious charge recombination associated with high metal impurity levels. Upgrading MG-Si close to solar grade is essential to achieve desired performance; nevertheless, the traditional silicon refinement process is cost ineffective, has high energy consumption, and causes environmental pollution. Here, we address this critical issue by employing a roomtemperature one-step Cu-assisted chemical etching (CuACE) process, which successfully purifies MG-Si into active photocatalysts. We discover that the use of reducing agent (H 3 PO 3 ) instead of commonly employed oxidant (H 2 O 2 ) in the etchant system induces a novel phenomenon called "chemical cracking effect". This effect significantly decreases the granularity of bulk MG-Si particles and simultaneously exposes fresh surfaces carrying impurities to the acids. This induces CuACE with promising purification rates, where major removal efficiencies of metal impurity reach 98.2% for Fe, 62.6% for Ca, and 61.0% for Al. Also, purified MG-Si exhibits excellent photocatalytic activity toward methyl orange (MO) degradation. Our approach provides new insights into metal-assisted chemical etching (MACE) of dirty silicon and opens a path for utilization of MG-Si in heterogeneous photocatalysis.